Submarine geology and geophysics

OLR (1989) 36 (7) 573

A theoretical treatment is presented for the evap- oration rate of specific hydrocarbons from crude oil spills. The fraction remaining of a specific hydrocarbon at any given evaporative exposure (directly related to time) can be calculated from the hydrocarbon's vapor pressure. Experimental data from four crude oils support the theory and define the one unknown parameter. In addition, a technique is developed to predict fresh oil composition based on a weathered oil's composition and the weathered oil's initial boiling point. Dept. of Chem. Engng and Applied Chem., Univ. of Toronto, ON M5S 1A4, Canada.

89:3773 Svenson, Anders and H~ikan BjOrndal, 1988. A

convenient test method for photochemical transformation of pollutants in the aquatic environment. Chemosphere, 17(12):2397-2405.

A method (based on a modified Xenotest 1200) which has proved convenient for determination of photolytical degradation rates is described. The method was applied to testing of photochemical degradation of organic chemicals in aquatic media. Solutions of six chlorinated phenolic substances, 8-quinolinol and 9,10-anthraquinone were illumi- nated with filtered light, simulating daylight at

controlled conditions. Quantum yields of photochemical degradation and half lifetimes (of conversion) were calculated using a sun spectrum at 60°N. Swedish Environ. Res. Inst., P.O. Box 210 60, S-100 31 Stockholm, Sweden.

89:3774 Walker, W.W. et al., 1988. Biological and abiotic

degradation of xenobiotic compounds in in-vitro estuarine water and sediment/water systems. Chemosphere, 17(12):2255-2270. Gulf Coast Res. Lab., Ocean Springs, MS 39564, USA.

C240. Corrosion

89:3775 Kumar, Ashok and M.D. Armstrong, 1988. Cathodic

protection designs using ceramic-coated anodes. Mater. Perform., 27(10): 19-23. U.S. Army Con- struction Engng Res. Lab., 2902 Newmark Dr., Champaign, IL 61820-1305, USA.

89:3776 Lye, R.E., 1988. Current drain to cathodically

protected stainless steels in seawater. Mater. Perform., 27(10):24-28. Norsk Hydro, Res. Cen- tre, N-3900 Porsgrunn, Norway.

D. SUBMARINE GEOLOGY AND GEOPHYSICS

DIO. Apparatus and methods

89:3777 Duijndam, A.J.W., 1988. Bayesian estimation in

seismic inversion. Part I. Principles. Geophys. Prospect., 36(8):878-898.

The specification and use of a priori distribution have long been disputed by statisticians--the fully 'objective" frequentists pitted against the Bayesian school that advocates the interpretation of probability through the weighing of subjective factors. In this first of two papers Bayesian theory and estimation fundamentals are outlined. The subsequent paper will examine detailed inversion of post-stack seismic data, and also discuss uncertainty and

resolution analysis. However much rigorous statisticians may spurn Bayesian arguments, the author finds them 'more convincing' and the results 'more encouraging.' Using 'a priori information can strongly improve estimation results. It solves the problems of non-uniqueness and instability.' Delft Geophys. B.V., P.O. Box 148, 2600 AC Delft, Netherlands. (fcs)

89:3778 Duijndam, A.J.W., 1988. Bayesian estimation in

seismic inversion. Part ll. Uncertainty analysis. Geophys. Prospect., 36(8):899-918.

Bayesian estimation combines information from the output of an information system (data), which is

574 D. Submarine Geology and Geophysics OLR (1989) 36 (7)

reduced to a likelihood function, with a priori information (independently obtained or inferred) on the parameters, which is reduced to an a priori probability density function. The product of the two, the a posteriori pdf, is the solution to the inverse problem. However, the solution is incomplete without a full analysis of uncertainty. In this second of two papers, uncertainty analysis (resolution) is discussed at length in the application of Bayesian techniques to post-stack seismic data analysis. Delft Geophys. B.V., P.O. Box 148, 2600 AC Delft, Netherlands. (fcs)

89:3779 Milenkovi~, B.S., 1989. Verification of the hypothesis

regarding the random nature of fluctuation of geological properties. J. Geol, 97(1): 109-116. U1. Generala Pavla Ilica 2/9, 19210 Bor, Yugoslavia.

89:3780 Qu, Gaosheng, 1988. Quantitative mineralogical

analysis of carbonate sediments by X-ray diffraction. Mar. Geol. Quat. Geol., 8(2):53-66. (In Chinese, English abstract.) Inst. of Mar. Geol., Min. of Geol. and Mineral Resour., Qingdao, People's Republic of China.

89:3781 Sarda, N. and D. Matthews, 1988. An efficient

storage structure for bethynletric data. Light- house, 38:15-20.

To obtain a representation of the ocean bottom bathymetry for the purpose of channel dredging, it is necessary to observe and record the depths over virtually every square meter of surface for which modelling is required. Extracting the desired information from the large quantities of data collected by surveying is time-consuming and expensive. This paper presents an alternative to the storage system currently employed by the Department of Public Works. The rationale for the system design is given, and the result of processing actual data is indicated as a measure of the system's performance.

89:3782 Tsujiura, Masaru, 1988. Characteristic seismograms.

Bull. Earthq. Res. Inst., Univ. Tokyo, Suppl. Vol. V:1-212.

Two decades of records from the Dodaira seismic network were systematically culled in order to make a worldwide catalog of seismograms typical of individual regions. One hundred representative seismograms are presented along with basic analysis and comments on their characteristics. The seismograms are arranged by seismic region and presented in order of their epicentral distances and

depths. Usual and unusual seismic waveform features of each region are noted. Earthquake Res. Inst., Univ. of Tokyo, Japan. (fcs)

D40. Area studies, surveys, bathymetry

89:3783 Chang, Chengfa, R.M. Shackleton, J.F. Dewey and

Jixiang Yin (project leaders), 1988. The geological evolution of Tibet. Report of the 1985 Royal Society-Academia Sinica Geotraverse of Qinghai-Xizang Plateau. Phil. Trans. R. Soc., (A)327(1594):1-413; 14 papers.

The Tibetan Plateau, 5 km above sea level with a crust twice normal thickness, is the result of the collision of the Indian and Eurasian continents. Although the general character of the plateau has long been known, much of it has been inaccessible to foreign geologists. The opening of a road across central and northern Tibet, connecting Lhasa to Golmud, provided an opportunity to obtain significant new information on the area, and in June 1985 a cooperative venture involving ten Royal Society and fifteen Academia Sinica geologists embarked on a traverse across the plateau. The results available to date are presented in this volume and include data on regional stratigraphy, paleontology, sedimentol- ogy and paleoecology; plutonic, volcanic, and metamorphic rocks; ophiolites; paleomagnetics; isotope geochemistry; geological mapping; structure; Quaternary faulting; Cenozoic uplift and deformation; and the tectonic evolution of the plateau. (hbf)

D 6 0 . G e o m o r p h o l o g y (fans, canyons, etc.)

89:3784 Barnes, P.W. and Reidar Lien, 1988. Icebergs rework

shelf sediments to 500 m off Antarctica. Geology, geol. Soc. Am~ 16(12):1130-1133.

The action of iceberg keels and sea ice can produce both diamicts and ice gouge features (subcircular depressions, 'washboard' patterns, and hummocky beds) that can be misinterpreted as evidence for glacially-derived strata and glaciation. On the continental shelf off Antarctica gouges 15 m in depth, 350 m wide with lengths > 15 km occur under shelf waters hundreds of meters deep. On the basis of studies of the submarine bank tops and slopes off Wilkes Land and in the Weddell Sea, it is concluded that a poorly stratified diamicton, modern ice-keel turbate, probably occurs over large areas of the

OLR (1989) 36 (7) D. Submarine Geology and Geophysics 575

Antarctic shelf. USGS, Menlo Park, CA 94025, USA. (hbf)

D70. Coasts, beaches, marshes

89:3785 Friedrichs, C.T. and D.G. Aubrey, 1988. Nonlinear

tidal distortion in shallow well-mixed estuaries: a synthesis. Estuar. coast. Shelf Sci., 27(5) :521-545.

The importance of asymmetric tidal cycles in the transport and accumulation of sediment in shallow well-mixed estuaries is well documented at 54 tide gauges in 26 tidally dominated estuaries of varying geometry having negligible freshwater inflow. Ana- lyses of sea-surface heights are compared to the results of one-dimensional numerical modelling to clarify the physics of tidal response in well-mixed estuaries. Concise measurements of estuarine geometry and ocean tidal range are used to predict consistently the nature of tidal sea-surface distortion. Numerical modelling then is utilized to extend theoretical and observational relationships between geometry and sea-height to predict trends in velocity distortion and near-bed sediment transport. WHOI, Woods Hole, MA 02543, USA.

89:3786 Griggs, G.B. and J.F. Tait, 1989. Observations on the

end effects of seawalls. Shore Beach, 57(1):25-26.

Biweekly or monthly visual observations and surveys of several different types of seawalls around Mon- terey Bay (central California) made over a period of two yr yield data on end sections or return walls at the downcoast or downdrift ends that show the downcoast extent of effects is related primarily to wave height and wave period, or arrival time of the next incoming wave. End geometry, permeability of structure, angle of wave approach, and tidal stage also influence end effects. A lowered beach profile was detected over an arcuate area of scour extending as far as 150 m down coast. The importance of wall length to downcoast effect is questioned, but the seaward extent of the structure, particularly in the case of groins, plays a significant role in determining downcoast impact. Dept. of Earth Sci., Univ. of Calif., Santa Cruz, CA, USA. (hbf)

89:3787 Grosswald, M.G., 1989. 'Submerged shorelines' on

glaciated continental shelves: solving the puzzle? J. coast. Res., 5(1):113-121.

A hypothesis is proposed which has been based upon an analysis of physical processes operating at the grounding line of the Ross Ice Shelf, Antarctica. It

suggests that the submarine terrace-shaped benches of glaciated shelves were formed at the grounding lines of the Pleistocene marine ice sheets, well below the former sea levels. Consequently, present-day depths of the benches cannot indicate the sea levels of the past. Inst. of Geogr., Acad. of Sci., 29 Staromonetny St., Moscow 109017, USSR.

89:3788 Hanson, Hans, 1989. Genesis---a generalized shore-

line change numerical model. J. coast. Res., 5(1):1-27.

The model is based on the one-line theory, for which it is assumed that the beach profile remains un- changed, thereby allowing beach change to be described uniquely in terms of the shoreline position. A simple user interface allows the system to be applied to a diverse variety of situations involving almost arbitrary numbers, locations, and combi- nations of groins, jetties, detached breakwaters, seawalls, and beach fills. Other features included are wave shoaling, refraction, and diffraction; sand passing through and around groins, and sources and sinks of sand. An overview of the modeling system is presented, and comparisons to analytic solutions as well as prototype situations are presented. Dept. of Water Resour. Engng, Lund Inst. of Tech., Univ. of Lund, S-221 00, Sweden.

89:3789 Hardisty, J. and A.J. Laver, 1989. Breaking waves on

a macrotidal barred beach: a test of McCowan's criteria. J. coast. Res., 5(1):79-82.

The location of the breakpoint on a macrotidal beach can vary in a discontinuous manner due to the presence of longshore bars. Here we extend analyses to test predictions of the location of the breakpoint on a barred profile against observations. The results continue to support the theoretical analysis of McCowan (1894) and suggest that a value of 0.78 for the ratio of the wave height to the water depth at the breakpoint can be used to model breaker location to + 5 m on a 300-m-wide intertidal profile. Dept. of Geogr., Royal Holloway and Bedford New Coll., London Univ., Egham, Surrey, TW20 0EX, UK.

89:3790 Hill, J.M. and P. Turnipseed, 1989. Spatial analysis

of coastal land loss by soft type [in I.xmislana]. J. coast. Res., 5(1):83-91. Dept. of Civ. Engng, Louisiana State Univ., Baton Rouge, LA 70803, USA.

89:3791 Kostachuk, R.A. and J.L. Luternauer, 1989. The role

of the salt-wedge in sediment resnspension and


deposition: Fraser River Estuary, Canada. J. coast. Res., 5(1):93-101.

Results from channel surveys of the Fraser River Estuary indicate that resuspension and deposition of sandy bed-material are affected by the salt-wedge. As the tide rises, the salt-wedge migrates into the channel and rapid deposition of suspended bed- material occurs. This is related to interference in the pattern of sediment exchange between the flow and the bed and reduced turbulence in the upper layer. During falling tides the salt-wedge moves seaward and resuspension begins as the tip of the wedge passes, in response to enhanced turbulence, and is then sustained by accelerating downstream flows. Dept. of Geogr., Univ. of Guelph, ON N I G 2Wl, Canada.

89:3792 Lippmann, T.C. and R.A. Holman, 1989. Quanti-

fication of sand bar morphology: a video technique based on wave dissipation. J. geophys. Res., 94(C1):995-1011.

A technique is presented to remotely measure the scales and morphology of natural sand bars based on the preferential dissipation of wind waves and swell over the crests of the bar. Photographic or video images are recorded and statistical uncertainties associated with incident wave height mod- ulations removed by averaging. However, during high waves, persistent surface foam obscures the relationship of image intensity to local dissipation, and an enhancement technique of image differenc- ing must be done to remove the bias. Errors in the estimate of bar crest distance from the shoreline are generally ~35%, but this value depends on the geometry of the particular bar. Logistic simplicity and quantitative capabilities make this technique very attractive. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA.

89:3793 Moore, G.W. and J.G. Moore, 1988. Large-scale

bedforms in boulder gravel produced by giant waves in Hawaii. Spec. Pap. geol. Soc. Am., 229:101-110.

An analysis of sedimentary structures on and within the beds of the Hulopoe Gravel on Lanai supports the hypothesis that the formation is the product of a giant wave train that resulted from the huge submarine landslide ~ 5 0 km southwest of Lanai at ~105,000 yrBP. At its type location in a bayhead gulch about 22 m above sea level and 200 m from shore, the deposit consists of three beds, 2, 4, and 2 m thick, each with a lower unit of basalt and limestone boulders, cobbles, and sand and an upper

unit of basalt boulders in a pebbly-sand matrix. The paired units are interpreted as being laid down by the runup and backwash of each wave. Dunelike ridges of basalt boulders are found locally on the upper surface of the gravel. Landward-dipping, imbricated clasts at the bed boundaries may be due to torrential flow and crossbedding created by the backwash. Dept. of Geol., Oregon State Univ., Corvallis, OR 97331, USA. (hbf)

89:3794 Morton, R.A., 1988. Nearshore responses to great

storms. Spec. Pap. geol. Soc. Am., 229:7-22.

Great storms, particularly on low-energy coasts, are responsible for the production of large geomorphic features and bedforms and much of the coarser- grained basin fill. During peak storm intensity the coarse sediments are transported by unidirectional currents. As storm intensity subsides, orbital wave motion controls sand deposition and is succeeded by settling of fine particles from suspension, creating graded storm bed units with a thickness that varies directly with wave and current energy and flow duration and inversely with distance from shore. A comparison of modern storm deposits with their ancient counterparts shows many similarities in sedimentologic properties, texture, structure, and vertical sequence, suggesting that the products of the hypothetical super storm are either unrecognized or unimportant in the overall geologic record. Bur. of Economic Geol., Univ. of Texas, P.O. Box X, Austin, TX 78713, USA. (hbf)

89:3795 Nakashima, L.D., 1989. Shoreline responses to

hurricane Bonnie in southwestern Louisiana. J. coast. Res., 5(1):127-136. Louisiana Geol. Sur- vey, P.O. Box G, Univ. Sta., Baton Rouge, LA 70893, USA.

89:3796 Nuttle, W.K., 1988. The extent of lateral water

movement in the sediments of a New England salt marsh. Wat. Resour. Res., 24(12):2077-2085.

Models of depth-averaged hydraulic head are used with data from a water balance study to describe horizontal pore water fluxes near a creek bank. Three hydrologically distinct regions are identified in the sediment. In the marsh studied, semidiurnal tides may drive an oscillating horizontal flux in the narrow region within ~2 .5 m of the creek bank;

15 m from the creek there is no horizontal water movement. Between 2.5 and 15 m, drainage to the creek is driven by alternating periods of surface flooding and nonflooding. There is little or no input of fresh groundwater at this site. The spatial extent


of the drained region depends on the duration of the nonflooded period, morphology of the sediment surface, and the ratio of hydraulic conductivity to specific storage of the sediment. Dept. of Environ. Sci., Univ. of Virginia, Charlottesville, VA 22903, USA.

89:3797 Pilkey, O.H. and T.D. Clayton, 1989. Summary of

beach replenishment experience on U.S. east coast barrier islands. J. coast. Res., 5(1): 147-159.

This paper summarizes data on the occurrence of beach replenishment on the U.S. east coast, listing the date, volume, length, and cost of each emplace- ment operation, as well as funding source. The amount of data available is quite variable and much information is lacking. A 'broad brush' overview of these data has previously been published (Pilkey and Clayton, 1987), and more detailed analyses are presently in preparation. Dept. of Geol., Duke Univ., Durham, NC 27708, USA.

89:3798 Psuty, N.P. (ed.), 1988. Dune/beach interaction.

Proceedings of a special session, Annual Meet- ing of the Association of American Geogra- phers, Portland, Oregon, April 1987. J. coast. Res., (Spec. Iss.)3:136pp; 22 papers.

Long, multiple-page abstracts of the twenty-two presentations made at the annual meeting by researchers from ten countries are published in this special issue in the hope that in total they provide a timely state-of-the-art summary of studies of dune/ beach interaction. Among the numerous subjects covered are sediment budget; the surf zone, beach, beach ridge, foredune, and mobile dune environments; geomorphological, sedimentological, and pedological factors; quartz grain textures; erosion and accretion; seasonal processes; cyclical changes; artificial construction of foredunes; dune crest mobility; eolianite and eolian transport; and effects of changing sea level. Geographic areas covered include Victoria and southeast Australia; Ireland and northwest England; Portugal, Spain, and Bel- gium; Putuo Island and Fujian, China; Algoa Bay and South Africa; Chile; and Long Island, Loui- siana, and Lake Erie, in the U.S. (hbf)

89:3799 Samsuddin, M., 1989. Influence of seasonal changes

on the texture of beach sands, southwest coast of India. J. coast. Res, 5(1):57-64. Centre for Earth Sci. Studies, P.O. Box 7250, Akkulam, Trivan- drum 695 031, India.

89:3800 Smith, A.W.S., 1989. Reflected edge waves. Shore

Beach, 57(1):20-22.

Beach recession on the Gold Coast of Queensland, Australia is accelerated in the vicinity of 'hard' surface projections, such as revetments and groins, which are not perfectly parallel to the incoming wave train and which merge back into a generally parallel beach face. During storm conditions the higher- than-normal wave attack produces an incoming wash that refracts around the oblique 'hard' surface and is then reflected ~90 ° to that surface as an edge wave. The energy of the edge wave (roughly two-thirds that of the incoming wave) is picked up by incoming beach-parallel waves. The higher- energy waves produce a much flattened beach and localized recession. The unusually high local surge levels also result in wave action further up the beach berm, adding to the recession rate. (hbf)

D80. Reefs and atolls

89:3801 Bourrouilh-Le Jan, F.G. and L.C. Hottinger, 1988.

Occurrence of rhodolites in the tropical Pacific-- a consequence of Mid-Miocene paleoceanographic change. Sedim. Geol., 60(1-4):355-367.

Rhodolites occurring over wide areas of the tropical Pacific are dated in many places by diagnostic larger Foraminifera as of Middle Miocene age. They are preceded in Early Miocene and succeeded in Late Miocene by hermatypic coral deposits. The processes linking this facies change with time to paleo- oceanographic events documented in deep-sea sediments are identified as sea-level rise drowning the reefs, a slight drop of winter SST and an increase in the fertility of surface waters inhibiting compen- satory growth of hermatypic corals until sea-level fall restored the earlier, original conditions of deposition. Lab. de Geol. Sedimentol. comparee et applique, Univ. de Pau, 64000 Pau, France.

89:3802 Grigg, R.W. and David Epp, 1989. Critical depth for

the survival of coral islands: effects on the Hawaiian Archipelago. Science, 243(4891):638- 641.

Coral islands drown when sea level rise exceeds the maximum potential of coral reefs to grow upward. During the Holocene transgression sea levels rose at rates of up to l0 to 20 millimeters per year, and most coral island reefs situated deeper than a critical depth of 30 to 40 meters below present day sea level


drowned. Coral islands that did not drown apparently all developed on antecedent foundations shallower than critical depth. During low stands in sea level during the Pleistocene, these islands were elevated and subject to subaerial erosion. Today, the depth of drowned banks is inversely related to summit area. Bank summit area may therefore be an important factor determining the failure or success of coral islands. ®1989 by AAAS. Hawaii Inst. of Mar. Biol., Univ. of Hawaii, Honolulu, HI 96822, USA.

89:~803 Hallock, Pamela et al., 1988. Platforms of the

Nicaraguan Rise: examples of the sensitivity of carbonate sedimentation to excess trophic re- s o u r c e s . Geology, geol. Soc. Am., 16(12):1104- 1107.

No coral reef development has been discovered on the Nicaraguan Rise carbonate platforms in the tropical waters of the western Caribbean; instead, sponge-algal communities dominate the drowning surfaces. The importance of trophic resources to coral reef development is indicated by the distribution of the coral-algal benthos across the region and the corresponding west-east gradient of biotic pigments in surface waters. Dept. of Mar. Sci., Univ. of South Florida, St. Petersburg, FL 33701, USA. (hbf)

89:3804 Riddle, M.J., 1988. Cyclone and bioturbation effects

on sediments from coral reef lagoons. Estuar. coast. Shelf Sci., 27(6):687-695. Australian Inst. of Mar. Sci., PMB No. 3, Townsville MC, QLD 4810, Australia.

D 1 I0. Erosion

89:3805 Malinverno, Alberto et al., 1988. Sonar images of the

path of recent failure events on the continental margin off Nice, France. Spec. Pap. geol. Soc. Am., 229:59-76.

A SeaMARC I survey of the continental margin off Nice, France, the site of a tsunami associated with a submarine slide which submerged about 100 km of coastline on October 16, 1979, reveals the presence of steep-sided canyons with hanging tributary gullies and badland topography that is compared to the giant bedforms in the Channeled Scabland of eastern Washington. The 80-km image path details the features of a scoured surface with depressions up to 70 m deep, produced by erosion of the underlying

sediments; although there is evidence of extensive substrate reworking, there has been little if any deposition. Lamont-Doherty Geol. Observ., Pali- sades, NY 10964, USA. (hbf)

89:3806 Mullins, H.T. and A.C. Hine, 1989. Scalloped bank

margins: beginning of the end for carbonate platforms? Geology, geol. Soc. Am., 17(1):30-33.

Bathymetric, seismic, and satellite data have revealed the presence of a 'new' type of erosional carbonate bank common to much of the Gulf of Mexico and the Caribbean. These banks may be tens of kilometers across with irregular shapes and convex-bankward embayments formed by large- scale failure triggered by earthquakes or dissolution and/or current undercutting along the platform margin. It is suggested that the small, isolated banks found in the Bahamas may be only remnants of former large platforms and may signal the demise of carbonate platforms in that area. Dept. of Geol., Syracuse Univ., Syracuse, NY 13244, USA. (hbf)

D120. Sedimentary processes (deposition, diagenesis, etc.)

89:3807 Clifton, H.E. (ed.), 1988. Sedimentologic conse-

quences of convulsive geologic events. Spec. Pap. geol. Soc. Am., 229:157pp; 11 papers.

This volume is an outgrowth of a symposium held in Orlando, Florida, during the October 1985 meeting of the Geological Society of America. Included are reports describing a number of relatively infrequent, high-energy, convulsive geological events that have left their mark on the sedimentary record: great storms along the nearshore; the eruptions of Mount St. Helens in the past decade and Mount Mazama ~6900 yrBP; submarine failure on the continental margin off Nice, France; the 1929 Grand Banks earthquake; turbidity current action on basin plains; giant waves in Hawaii; floods in the Late Wiscon- sinan Wabash Valley; a Mid-Tertiary happening in the San Emigdio Range, southern California; and the K /T boundary event. (hbf)

89:3808 Farrow, G.E. and J.A. Fyfe, 1988. Bioerosion and

carbonate mud production on high-latitude shelves. Sedim. Geol~ 60(1-4):281-297.

Low-latitude carbonate muds are often composed of entire units of skeletons or precipitates, whereas high-latitude carbonate muds are bioerosional or


result from maceration. Bioerosion at high latitudes is very rapid and most intense in the photic zone, particularly down to 25 m depth. Shelly substrata may be crushed, bitten, drilled, bored, or scraped. Clionid sponges, endolithic algae, acmaeid gastropods, and echinoids are the most significant agents. The mud fraction of northwest European shelf sediment generally contains 10-20% CaCO3, and some Holocene supratidal mud-flats exceed 50%. Much of the shelf represents a modern-day equivalent of the 'calcareous shale' facies common in the geological record. British Geol. Survey, Murchison House, W. Mains Rd., Edinburgh EH9 3LA, Scot- land, UK.

89:3809 Pilkey, O.H., 1988. Basin plains: giant sedimentation

events. Spec. Pap. geol. Soc. Am., 229:93-100.

A summary of data on thirteen of the huge basin plains found at the seaward end of continental margin sediment transport systems in the western North Atlantic, Caribbean, and Mediterranean basins, demonstrates that they are fundamentally the product of turbidity currents. Although the plains are composed in part of hemipelagic sediments (up to 20%) and some debris flows, they are largely filled by turbidity currents, which not only supply large volumes of sediments debauched from canyon mouths on the continental margin, but also produce the flat plain floors. The largest turbidity event sampled to date is the Black Shell Turbidite of the Hatteras Abyssal Plain, which alone was responsible for deposition of at least 100 km 3 of sediment. Dept. of Geol., Duke Univ., Durham, NC 27708, USA. 0abf)

89:3810 Piper, D.J.W., A.N. Shor and J.E. Hughes Clarke,

1988. The 1929 'Grand Bank¢' earthquake, slump, and turbidity current. Spec. Pap. geol. Soc. Am., 229:77-92.

Unpublished data collected between 1981 and 1985 and previously published studies on the area of the 1929 event, which was triggered by an M s = 7.2 earthquake on the continental slope above the Laurentian Fan and moved at least 175 km 3 of sediment within a huge lobe on the Sohm Abyssal Plain, are summarized. Although an earthquake of this magnitude probably occurs every few hundred years along the eastern Canadian margin, there is no evidence of similar scale turbidite deposits in the region, and it is suggested that such a convulsive event requires not only a large triggering earthquake but also the availability of large quantities of coarse sediments at an appropriate depth. Atlantic Geosci.

Centre, Bedford Inst. of Oceanogr., P.O. Box 1006, Dartmouth, NS B2Y 4A2, Canada. (hbf)

89:3811 Prior, D.B., E.H. Doyle and M.J. Kaluza, 1989.

Evidence for sediment eruption on deep seafloor, Gulf of Mexico. Science, 243(4890):517-519.

A large crater has been discovered on the seafloor, Gulf of Mexico, in a water depth of 2176 meters. Deep-tow high-resolution imagery shows that the crater is cut into a low hill surrounded by near- surface concentric faults. Approximately 2 million cubic meters of ejected sediment forms a peripheral debris field. The low hill and faults may be related to mud diapirism or intrusion of gas hydrates into near-surface sediments. A recent eruption evacuated sediments from the crater, apparently because of release of overpressured petrogenic gas. ©1989 by AAAS. Coastal Studies Inst., Louisiana State Univ., Baton Rouge, LA 70803, USA.

89:3812 Reeckmann, S.A., 1988. Diagenetic alterations in

temperate shelf carbonates from southeastern Australia. Sedim. Geol., 60(1-4):209-219.

Temperate shelf carbonates have skeletal and mineralogical compositions unlike their tropical counterparts, commonly lacking non-skeletal grains and often composed of low- and high-Mg calcite with only subordinate aragonite. Diagenesis takes place in marine waters with lower carbonate saturation. Marine cementation is rare. Diagenetic stabilization of aragonite and high-Mg calcite has taken at least 80,000 yr during subaerial exposure. The lack of aragonite leads to lack of secondary porosity and only sparse low-Mg calcite cement, even after prolonged freshwater diagenesis. In sequences containing siliciclastic clays, pyrite, and glauconite, abundant iron in interstitial waters leads to precipitation of ferroan calcite cements. A unique, void- filling micritic, low-Mg calcite layer with pink/brown coloration, found in many Tertiary temperate shelf carbonate sequences, is a feature of the vadose zone. Exploration Dept., Esso Australia, GPO 4047, Sydney, NSW 2000, Australia.

89:3813 Smith, A.M., 1988. Preliminary steps toward for-

marion of a generalized budget for cold-water carbonates. Sedim. Geol, 60(1-4):323-331.

Rates of gross production, net production, and diagenesis were investigated at Shell Beach in the Gulf of Maine, a shelly pocket beach. Gross production by dominant organisms was calculated to be 1600 g CaCO3/m 2 per y over the area of


production. Net production was on the order of 13-130 g CaCO3/m 2 y. The difference is explained by strong, destructive diagenesis, dominantly biological, and at a rate of 80-1300 g CaCOa/m 3 y. The large gap between gross and net production seems to be characteristic of cold-water carbonate sediments, as does the strongly destructive diagenesis. The gap must be remembered when assessing fossil cold- water populations. Dept. of Earth Sci., Univ. of Waikato, Private Bag, Hamilton, New Zealand.

89:3814 Strasser, Andr~ and Paul Bernier, 1988. Early

diagenetic ferruginous cementation in the intertidal zone: example from Noirmoutier Island, France. Oceanologica Acta, 11(4):353-357. Dept. de Geol. et Paleontol., Univ. de Geneve, 13, rue des Maraichers, 1211 Geneve 4, Switzerland.

89:3815 Weedon, G.P., 1989. The detection and illustration of

regular sedimentary cycles using Walsh power spectra and filtering, with examples from the Lias of Switzerland. J. geol. Soc., Lond., 146(1): 133- 144. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK.

89:3816 Wilson, J.B., 1988. A model for temporal changes in

the faunal composition of shell gravels during a transgression on the continental shelf around the British Isles. Sedim. Geol., 60(1-4):95-105. Inst. of Oceanogr. Sci., Deacon Lab., Wormley, Godalming, Surrey, UK.

89:3817 Young, H.R. and C.S. Nelson, 1988. Endolithic

biodegradation of cool-water skeletal carbonates on Scott shelf, northwestern Vancouver Island, Canada. Sedim. Geol., 60(1-4):251-267.

Biodegradation of shell material is widespread in the deposits on Scott shelf, especially in the large aragonitic bivalves, Glycymeris and Humilaria. Ten types of endolithic microborings have been identified in the shells, including green algae, blue-green algae, fungi, bacterial, and clionid sponges, as well as macroborings of phoronids, polychaetes, and naticid gastropods. Boring physically weakens the shells, rendering them more prone to mechanical and biological abrasion. Boring also increases the porosity and surface area of skeletal grains and destroys their organic matrix, making them susceptible to maceration and dissolution. Many aragonitic shells have become thoroughly degraded within ~ 1000 yr in ambient seawater. Such selective taphonomic loss of skeletal material may be considerable in ancient

temperate-shelf limestones. Dept. of Geol., Brandon Univ., Brandon, MB R7A 6A9, Canada.

D130. Sediments (rocks, formations, type, composit ion, etc.)

89:3818 Blom, W.M. and D.B. Alsop, 1988. Carbonate mud

sedimentation on a temperate shelf: Bass Basin, southeastern Australia. Sedim. Geol., 60(1-4): 269-280.

Calcite carbonate muds are accumulating in relatively shallow (70-85 m) water depths in the central part of Bass Basin. Produced by primary accumulation and disintegration of nannoplankton and biodegradation of skeletal carbonate grains, the muds occur in the lowest-energy environment, are up to 1 m thick in the central basin and thin toward the basin margins. Bioturbation modifies their texture by increasing grain size as fecal pellets, creating a seafloor not in equilibrium with hydrodynamic conditions. Radiocarbon dates are 10,290_+250 to 11,660_+300 yrBP for an early post-glacial marine transgression embayment facies and 8700_+ 710 yrBP for the base of the modern strait facies, implying a Holocene sedimentation rate of ( 1 2 cm/k.y, for the basin center, falling to ( 6 cm/k.y, toward the margins. Dept. of Geol. and Geophys., Univ. of Sydney, NSW 2006, Australia.

89:3819 Bryant, W.R. and R.H. Bennett, 1988. Origin,

physical, and mineralogical nature of red clays: the Pacific Ocean Basin as a model. Geo-Marine Letts, 8(4): 189-249.

Extensive examination of North Pacific Basin red clays by scanning and transmission electron mi- croscopy reveals that the mean constituents are illite-rich argillaceous or shale clasts, quartz, and authigenic smectite. The main source of the shale clasts and quartz are eolian and are derived mainly from African and Asian shales. Geotechnical examination of the clays indicates that they are overconsolidated, attributed to the strong bonding of argillaceous or shale clasts, quartz, and other particulate matter by x-ray amorphous and crystalline sheets of authigenic smectite characterized by high surface activity. Dept. of Oceanogr., Texas A&M Univ., College Station, TX 77843, USA.

89:3820 Collins, L.B., 1988. Sediments and history of the

Rottnest Shelf, southwest Australia: a swell- dominated, non-tropical carbonate margin. Sedim.

OLR (1989) 36 (7) D. Submarine Geology and Geophysics 58/

Geol., 60(1-4):15-49. Dept. of Geol. and Geophys., Curtin Univ. of Tech., G.P.O. Box U 1987, Perth, WA 6001, Australia.

89:3821 DuBois, L.G. and W.L. Prell, 1988. Effects of

carbonate dissolution on the radiocarbon age structure of sediment mixed layers. Deep-Sea Res., 35(12A): 1875-1885.

Cores from the tropical Atlantic show the effects of a depth-dependent relationship between dissolution and bioturbation. The age of the mixed layer becomes younger in cores taken from >4400 m water depth. Solution-induced modification of the carbonate sediment coincides with change in age structure. The interaction of bioturbation with dissolution in sublysocline cores produces a bias in the observed radiocarbon age of the mixed layer toward young ages. Published observations of mixed layer ages in the equatorial Pacific show the reverse trend; mixed layer ages become older below the lysocline. The existence of Atlantic vs Pacific response patterns indicates the bioturbation/dissolution relationship is environment-dependent and time-varying. This conclusion has important implications for the interpretation of deep-sea sediment records. Dept. of Geol. Sci., Brown Univ., Provi- dence, RI 02912, USA.

89:3822 Gaillard, Christian, 1988. Recent bioturbation off

New Caledonia. Preliminary results of the Biocal cruise. Oceanologica Acta, 11(4):389-399. (In French, English abstract.) Centre des Sci. de la Terre, Univ. Claude Bernard-Lyon I, 69622 Villeurbanne Cedex, France.

89:3823 Gorbunova, Z.N., 1987. Highly dispersed minerals in

cores from the southwestern Pacific Ocean. Oceanology (a translation of Okeanologiia), 27(6):725-728. Shirshov Inst. of Oceanol., USSR Acad. of Sci., Moscow, USSR.

89:3824 Gostin, V.A., A.P. Belperio and J.H. Cann, 1988.

The Holocene non-tropical coastal and shelf carbonate province of southern Australia. Sedim. Geol., 60(1-4):51-70.

Carbonate-dominant sediments form and accumulate over the wide marine shelf of southern Australia, which is bathed by cold upwelling waters that support luxuriant biota. There is a dearth of continental detritus, and the open coast is battered by persistent southwest swell. Much sediment is reworked, and overall shelf sedimentation rates are

low. Tidal amplitude and currents establish a depth and inundation-related zonation of plants and animals. Muddy carbonate sand accumulates below 30 m, where bryozoans, bivalves and sponges dominate. Shallow seagrass meadows contain a rich fauna that results in rapid accumulation of unsorted, muddy bioclastic sand. Mangrove woodlands accumulate mud-rich, gastropod-bearing sediment. As tidal amplitude and desiccation increase, a supratidal zone bare of vegetation becomes the site for deposition of gypsum-rich and fenestral calcite mud. Dept. of Geol. and Geophys., Univ. of Adelaide, GPO Box 498, Adelaide, SA 5001, Australia.

89:3825 Hs0, K.J., 1988. Cretaceous/Tertiary boundary sed-

iment. Spec. Pap. geol. Soc. Am., 229:143-154.

The marly clay unit found in many parts of the world in both marine and continental sequences spanning the K/T boundary is described. In the marine sequence found at Caravaca, Spain, the clay includes a 0.5-cm basal lamina of red clay composed of impact ejecta, a thicker dark gray clay or marl of reworked extraterrestrial debris deposited in an oxygen-poor environment, and an overlying lighter gray clay that is transitional to Paleocene sediments. On land in the Raton Basin of New Mexico, the section includes a lower white clay made up of fine elastics, interpreted as fallout material, and an upper carbonaceous shale. Swiss Fed. Inst. of Tech., Zurich, Switzerland. (hbf)

89:3826 Kersten, Michael and Volker Klatt, 1988. Trace

metal inventory and geochemistry of the North Sea shelf sediments. Mitt. geoL-pal(lont. Inst. Univ. Hamb, 65:289-311.

Surficial sediments from the entire North Sea shelf were analyzed for lead, chromium, copper, zinc, manganese, iron, calcium, and organic carbon. Highest metal values were found in near-coast sediments off northeastern England, in the German Bight, and in the Fisher Bank, far away from major river input. Statistical analysis of the data indicates a non-natural source of the elevated metal concentrations. Biodeposition is discussed as a potential contributor to the enhanced heavy metal load found in the sediment fines of the central North Sea. Tech. Univ. Hamburg-Harburg, Eissendorfer Str. 40, D- 2100 Hamburg 90, FRG.

89:3827 Kounkou, G.L. and J.-P. Barusseau, 1988. Terrig-

enous sedimentation of the Upper Quaternary in the Cayar deep-sea fan (Senegal-Gambia Abyssal


Plain, Atlantic Ocean). Oceanologica Acta, 1 !(4):359-368.

A sedimentological and micropaleontological study of a Cayar deep-sea fan core, which bottoms in isotopic stage five, shows that the hemipelagic component remains generally constant except in the Holocene, where sedimentation rates are about three times greater. Turbiditic occurrences, abundant in all stages, seem more frequent during cold-to-warm transitions (arid-to-humid), coinciding with trans- gressive glacio-eustatic sequences. However, the Holocene displays a greater occurrence of turbidite layers with the shortest recorded periods. Lab. de Rech. de Sedimentol. Mar., Univ. de Perpignan, av. de Villeneuve, 66025 Perpignan, France.

89:3828 Kunzendorf, H., P. Stoffers and R. Gwozdz, 1988.

Regional variations of REE patterns in sediments from active plate boundaries. Mar. Geol., 84(3- 4): 191-199.

About 150 sediment samples from mid-ocean ridges and from a back-arc spreading environment were analyzed by instrumental neutron activation. A ratio method for rare-earth elements involving a plot of elemental ratios of Ce/La and La/Yb is proposed to characterize marine sediments. In the characteri- zation plot, East Pacific Rise and Lau Basin sediments occupy distinct fields, suggesting hydrothermal overprint, while sediments from the central Indian Ocean and the Carlsberg Ridge plot into the field for normal deep-sea sediments. Riso Natl. Lab., P.O. Box 49, DK-4000 Roskilde, Denmark.

89:3829 Land, L.S., J.A. Kupecz and L.E. Mack, 1988.

Lonann salt geochemistry (Gulf of Mexico sed- hnentary basin, U.S.A.): a preliminary synthesis. Chem. Geol., 74(1-2):25-35.

Samples of Jurassic salt and anhydrite obtained from the sedimentary basin have been analyzed for bromide content and 87Sr/S6Sr. Observations suggest that during deformation salt undergoes extensive rock-water interaction, losing bromide to reacting brines and incorporating radiogenic Sr. Similar behavior of anhydrite during deformation with respect to Sr is also observed. In general, the data suggest a dynamic system in which physical modification of evaporites during deformatign and deep burial is accompanied by chemical modification. Dept. of Geol. Sci., Univ. of Texas, Austin, TX 78713, USA.

89:3830 Nelson, C.S., S.L. Keane and P.S. Head, 1988.

Non-tropical carbonate deposits on the modern New Zealand shelf. Sedim. Geol., 60(1-4):71-94.

Extensive shallow-marine platforms off New Zea- land are blanketed by skeletal carbonate sediments. Terrigenous sediment supply is low, and growth of epibenthos is fostered by firm substrates and high nutrient levels. Rapid transition to terrigenous- dominated facies is characteristic. The dominantly calcitic carbonates are coarse-grained and fragmen- tal. Skeletal material is dominated by bryozoans and bivalve molluscs with significant local contributions from other biota. The name bryomol is suggested for this distinctive temperate-region skeletal carbonate facies. Bioerosion is important. The facies afford good analogues for onland occurrences of New Zealand Cenozoic limestones. Dept. of Earth Sci., Univ. of Waikato, Hamilton 2001, New Zealand.

89:3831 Nelson, C.S. (ed.), 1988. Special issue. Non-tropical

shelf carbonates---modern and ancient. Sedim. Geol., 60(1-4):367pp; 23 papers.

The occurrence, genesis, and significance of non- tropical shelf carbonates (also termed cool-water, temperate-latitude and mid- or high-latitude carbonates) are explored in this special issue---the first compilation of papers dealing exclusively with these deposits--and provide a useful data base for future studies. There are four sections treating modern examples--shelf deposits of Australia and New Zealand, and the British Isles and Porcupine Bank in the NE Atlantic; ancient examples--the Mid-Or- dovician Black River and Trenton limestones of southern Ontario, Permian limestones in the southeastern Bowen Basin of Queensland, Permo-Triassic carbonates of Malaysia, Pliocene barnacle-dominated carbonates from Hawke's Bay in New Zea- land, and Cenozoic algal biostromes from northern Italy; diagenetic aspects and carbonate muds found in Australia, New Zealand, and Vancouver Island, Canada; and special aspects--application of bryo- zoan zoarial growth-form studies, a budget for cold-water carbonates, carbonate lithofacies as paleolatitude indicators, the fate of temperate-type carbonate platforms, and the significance of tropical Pacific rhodolites. Dept. of Earth Sci., Univ. of Waikato, Hamilton 2001, New Zealand. (hbf)

89:3832 Noorany, Iraj, 1989. Classification of marine sedi-

ments. J. geotech. Engng, Am. Soc. civ. Engrs, 115(1):23-37.

A new classification system is proposed for marine sediments based on the principle of soil mechanics and geology. The system can be used as an auxiliary


to the unified classification system. Marine sediments are divided into three major groups: terrigenous, biogenous, and hydrogenous, which are then subdivided. The system incorporates new symbols, consistent with those of the unified system, for all marine sediments. A classification chart is provided, and numerous examples are cited to illustrate application of the system. Dept. of Civ. Engng, San Diego State Univ., San Diego, CA 92182, USA.

89:3833 Ramesh, R. and V. Subramanian et al., 1989. The

elemental chemistry of sediments in the Krishna River Basin, India. Chem. Geol., 74(3-4):331-341.

Composition of bed, core and suspended sediments collected from the Krishna River were studied; observations are discussed in the light of other Indian rivers, world's average river suspended particles, surficial rock and soils. Suspended sediments are enriched (5 to l0 times) in all the elements considered relative to bed sediments; mobility of elements within the basin is controlled by basin geology, size and mineralogical characteristics. There is no systematic variation with depth for the major elements and the concentrations of most elements are considerably higher than in estuarine or Bay of Bengal sediments. Subramanian: Sch. of Environ. Sci., Jawaharlal Nehru Univ., New Delhi l l0 067, India.

89:3834 Salge, Uwe and H.K. Wong, 1988. The Skagerrak: a

depo-environment for recent sediments in the North Sea. Mitt. geol.-pal~ont. Inst. Univ. Hamb., 65:367-380. Geol.-Palontol. Inst. und Mus., Univ. Hamburg, Bundesstr. 55, D-2000 Ham- burg 13, FRG.

89:3835 Schmitz, Birger, 1988. Origin of microlayering in

worldwide distributed lr-rich marine Creta- ceous/Tertiary boundary clays. Geology, geol. Soc. Am., 16(12):1068-1072.

A study of the lithological and chemical microlayering of Ir-rich marine Cretaceous/Tertiary boundary clays from Denmark, Spain, and New Zealand reveals that the clays include a basal thin, red layer, largely locally derived and water transported, and an overlying organic-rich zone containing concentrations of Ir, Ni, Co, Cr, Zn, Cu, As, and Sb. The basal unit appears to represent precipitation from seawater, not fallout, and the metal concentrations most likely result from precipitation accompanying decomposition of the abundant algal matter on the end-Maastrichtian seafloor. It seems unlikely that the Ir-enrichment derives directly from

a global dust cloud raised by an asteroid impact, but the ultimate origin of some of the metals found in the marine clays may have been extraterrestrial. Dept. of Geol., Univ. of Stockholm, S-10691 Stock- holm, Sweden. (hbf)

89:3836 Scoffin, T.P., 1988. The environments of production

and deposition of calcareous sediments on the shelf west of Scotland. Sedim. Geol., 60(1- 4): 107-124.

Dominant calcareous organisms and sediment characteristics are described for eight shelf environments. Principal sites of carbonate production are shallow rocky substrates with barnacles, molluscs, echinoderms and serpulids; sheltered, shallow sandy zones where molluscs, echinoderms, and benthic foraminifers are the active producers although sediments are commonly barnacle-rich; between islands, where tidal currents are enhanced and waves suppressed and calcareous red algae and mussels build localized banks; and deep, open-shelf water where molluscs are major skeletal contributors to sediment. Well- sorted, cross-bedded, beach and dune sands commonly contain ~75% CaCO3, and in sheltered depressions bioturbated muds accumulate with up to 30% calcite silt, probably the breakdown product of barnacles and benthic foraminifers. Dept. of Geol., Univ. of Edinburgh, EH9 3JW, UK.

89:3837 Scoffin, T.P. and G.E. Bowes, 1988. The facies

distribution of carbonate sediments on Porcupine Bank, northeast Atlantic. Sedim. Geol., 60(1- 4):125-134.

Porcupine Bank (51-54°N, 12-15°W, ~10,000 km 2 in area and 150-500 m deep) is effectively removed from present-day terrigenous sedimentation. Water temperatures range from 10-14.5°C. Carbonate sediments presently accumulate on the bank, mixing with relict quartz sands and pebbles and boulders of glacial origin. The lithofacies have a crudely concentric zonation with pelagic foraminiferal oozes in the deepest waters passing to foraminiferal glau- conitic quartz sands over the bulk of the bank (500-200 m depths), where scattered patches of Lophelia pertusa coral are found, which in turn pass into a narrow zone at the bank crest (~200 m), which has coarse sands of quartz and skeletal fragments of benthic organisms. The similarity of the facies pattern to that of Rockall Bank, 500 km north, supports construction of a depth-related facies model for modern open-sea temperate carbonate sediments. Dept. of Geol., Univ. of Edinburgh, EH9 3JW, UK.


89:3838 von Haughwitz, Wolfram, H.W. Wong and Uwe

Salge, 1988. The mud area southeast of Helgo- land: a reflection seismic study. Mitt. geol.- pali~ont. Inst. Univ. Hamb., 65:409-422. Geol.- Palontol. Inst. und Mus., Univ. Hamburg, Bundestr. 55, D-2000 Hamburg 13, FRG.

89:3839 Wirth, Hans and M.G. Wiesner, 1988. Sedimentary

facies in the North Sea. Mitt. geol.-paldont. Inst. Univ. Hamb., 65:269-287.

Three sediment types were distinguished in North Sea sediments analyzed for grain-size, clay mineralogy, and organic carbon content: a mud facies in the inner German Bight and Skagerrak/Norwegian Channel; a mixed mud-sand facies in the Outer Silver Pit, the Oyster Grounds, Elbe Rinne, and parts of the central North Sea; and a sand facies covering the remaining platform. Clay mineral analysis showed that chlorite-rich material from the North Atlantic was temporarily deposited in the central and northern North Sea, whereas kaolinite- rich clays from continental sources were common in the southern North Sea and along the Danish coast. The major factor for the distribution of organic carbon was grain-size, which in <20 /~m fractions was almost constant except in a few areas of sand and mixed facies where carbon increased by a factor of two because of transitory deposition of fine- grained organic-rich material. Geol. Palaontol. Inst. und Mus. der Univ. Hamburg, Bundesstr. 55, 2000 Hamburg 13, FRG.

D140. Submarine hydrology (springs, hy- d r o the rma l deposi ts , etc.)

89:3840 Evans, W.C., L.D. White and J.B. Rapp, 1988.

Geochemistry of some gases in hydrothermal fluids from the southern Juan de Fuca Ridge. J. geophys. Res., 93(B12):15,305-15,313.

Five samples of hydrothermal fluids from two vent areas on the ridge were analyzed for dissolved gases. Concentrations in the end-member hydrothermal fluid of H2, CH4, and CO 2 are well above values in ambient seawater and are similar to concentrations reported for other ridge crest systems. The carbon isotopic ratios suggest that at least some of the CH 4 and CO 2 is basalt-derived. Small amounts of ethane, propane, and butane detected in the samples may also have formed in the basalt. One sample of almost pure hydrothermal fluid contained a significant fraction of the recharge Ar and N2, suggesting that

the fluid had not undergone extensive vapor-liquid phase separation. USGS, MS 434, 345 Middlefield Road, Menlo Park, CA 94025, USA.

89:3841 Fouquet, Yves et al., 1988. Geological setting and

mineralogical and geochemical investigations on sulfide deposits near 13°N on the East Pacific Rise. Mar. Geol., 84(3-4): 145-178.

Investigation of hydrothermal deposits on the EPR near 13°N, where there has been hydrothermal activity for >20,000 yr, shows that sulfides occur in four main tectonic settings: the middle and top part of the central graben, the marginal high, and the flank of the Southeastern Seamount. The sulfide samples exhibit a wide range of mineralogical assemblages which are dependent upon location; their classification into nine types is proposed. Hydrothermal activity at the axis is now increasing in intensity. The relative paucity of Zn-rich massive sulfides off-axis is likely due to depletion of Zn in hydrothermal fluids. R-mode factor analysis shows fractionation of reduced sulfur fluid during dis- charge into three groups displaying the principal types of sulfide samples collected. IFREMER, Centre de Brest, DERO/GM, B.P. 70, F-29263, Plouzane, France.

89:3842 Holm, N.G., 1988. Carbon isotope distribution in

organic matter and siderite of a modern metalliferous hydrothermal sediment and possible implications for gold associated with banded iron formation. Mar. Geol., 84(3-4):201-207.

Carbon isotope distribution in organic matter and siderite has been determined in the metalliferous sediments of Santorini, Greece. It has been proposed that the isotopically light carbon in carbonates of banded iron formations (BIF) is the result of 'dilution' of carbon in marine carbonates by isotopically light carbon from organic matter. A redistribution of some reduced carbon in newly precipitated ferruginous sediment to carbonate minerals in proportions found in some BIFs has been modelled in the present study. The isotopic shifts of the carbonate minerals were close to values observed in the geological record, suggesting organic matter was much more abundant during early phases of BIF development. The association of gold and reduced organic carbon is well established; it may be worthwhile to reevaluate the role of organic activity in deposition of BIFs and their potential as a source of gold. Dept. of Geol., Univ. of Stockholm, S-106 91 Stockholm, Sweden.


89:3843 Jensenius, Jorgen and N.C. Munksgaard, 1989.

Large scale hot water migration systems around salt diapirs in the Danish Central Trough and their impact on diagenesis of chalk reservoirs. Geochim. cosmochim. Acta, 53(1):79-88. Konin- klijke/Shell Explor. en Prod. Lab., Volmerlaann 6, 2288 GD Rijswijk ZH, Netherlands.

89:3844 Johnson, K.S., J.J. Childress and C.L. Beehler, 1988.

Short-term temperature variability in the Rose Garden hydrothermal vent field: an unstable deep-sea environment. Deep-Sea Res., 35(10- 11A): 1711-1721.

Temperature, measured over a period of 72 h within the animal communities of the vent field, ranged from a highest mean temperature of 5.54°C in the central clump of vestimentiferan worms to a lowest mean value of 2.26°C, recorded over the basaltic substrate. Temperature of the ambient water was 2.07°C. The site with the highest temperature was characterized by extreme variability in temperature, and in general, temperature fluctuated over all the time scales with no clear periodicity. However, these fluctuations must have a significant impact on adaptations by animals of the vent community. Mar. Sci. Inst., Univ. of Calif., Santa Barbara, CA 93106, USA.

89:3845 Lupton, J.E., E.T. Baker and G.J. Massoth, 1989.

Variable ~He/heat ratios in submarine hydrothermal systems: evidence from two plumes over the Juan de Fuca Ridge. Nature, Lond., 337(6203): 161-164.

The first vent fluid samples recovered from the Galapagos Rift and at 21°N on the EPR had a nearly identical ratio of 3He/heat, even though the two hydrothermal systems were separated geograph- ically and had widely differing fluid exit temperatures. A number of global estimates were then based on these results. Here we show that 3He/heat ratios vary by over an order of magnitude between submarine hydrothermal systems, suggesting that early measurements of the 3He/heat relation are not representative of all hydrothermal systems, and that flux calculations based on the oceanic 3He flux must be undertaken with caution. Mar. Sci. Inst., Univ. of Calif., Santa Barbara, CA 93106, USA.

89:3846 Marchig, V. et al., 1988. New discoveries of massive

sulfides on the East Pacific Rise. Mar. Geol., 84(3-4): 179-190.

Large occurrences of massive sulfides on the EPR between 18 ° and 24°S are restricted to zones characterized by relatively shallow bathymetric position and greater coverage with sheet rather than pillow lava, and greater than usual tectonic strain. Although animal communities that depend on sulfide oxidation are scarce and small, those that profit from the food supply provided by the primary fauna have dense populations over relatively large areas. Enrichment of the hydrothermal component in sediments adjacent to a spreading center is not typical of hydrothermal fields along the EPR. It can be concluded from evaluation of the sediment that hydrothermal activity increases northward. Fed. Inst. for Geosci. and Nat. Resources, P.O. Box 51 01 53, D-3000, Hannover 51, FRG.

89:3847 Nehlig, Pierre and Thierry Juteau, 1988. Deep crustal

seawater penetration and circulation at ocean ridges: evidence from the Oman Ophiolite. Mar. Geol., 84(3-4):209-228.

Detailed field mapping of the plutonic sequence and sheeted dike complex in several areas of the Sumail Ophiolite Nappe and comparison with other well- studied areas have shown that early hydrothermal circulation affected the whole crust down to the petrological Moho. Five major vein systems have been distinguished~amphibole, zoisite-epidote, epidote, quartz, and prehnite, each characteristic of a particular environment. Seawater diffusing from these veins penetrates the crust and induces retrograde metamorphic transformation such as hydra- tion, sodium gain, and leaching of calcium. Thermal gradients, deduced from fluid-inclusion micro- thermometric studies, decrease exponentially with depth and vary between 300C°/km in the volcanic unit and 30C°/km in the plutonic sequence. Lab. de Petrol., Univ. de Bretagne Occidentale 6, av. Le Gorgeu, F-29287 Brest Cedex, France.

89:3848 Oberh~nsli, R. and P. Stoffers (eds.), 1988. Special

issue. Hydrothermal activity and metalliferous sediments on the ocean floor. Mar. Geol., 84(3- 4):145-284; 9 papers.

Selected papers from a symposium on active hydro- thermalism and evidence for its ancient counterparts, held in conjunction with the 1987 EUG meeting in Strasbourg, are presented. Two papers describe active massive sulfide deposits on the East Pacific Rise; two others describe Mesozoic synsedi- mentary hydrothermal equivalents in the Alps. Other reports on present-day processes consider special geochemical aspects of modern sediments--REE patterns and carbon isotopes. The remaining papers


on evidence for ancient hydrothermal activity include two studies of the Oman ophiolite, and an investigation of a metamorphosed hydrothermal eruption breccia from the Austrian Alps. Geol. Inst. Eidgenoessich Tech. Hochschule-Zentrum, CH-8092 Zurich, Switzerland. (hbf)

89:3849 Schlosser, Peter et al., 1988. 3He in the Bransfield

Strait waters: indication for local injection from back-arc rifting. Deep-Sea Res., 35(12A):1919- 1935.

3He profiles from the eastern and central basins of the Bransfield Strait show maxima below the sill depths that separate the strait from the surrounding open ocean. The 3He excess is interpreted as a local injection of a 3He-rich helium component into Bransfield Strait deep waters from back-arc rifting. Tritiogenic 3He and excess 3He from mixing with Circumpolar Deep Water are excluded as possible sources. The estimated 3He/4He ratio of the injected helium component is less than that of pure mantle helium and may contain radiogenic helium from continental crustal material which underlies the Bransfield Strait. Inst. fur Umweltphysik, Univ. Heidelberg, Im Neuenheimer Feld 336, D-6900 Heidelberg, FRG.

89:3850 Varnavas, S.P., 1989. Submarine hydrothermal me-

taliogenesis associated with the collision of two plates: the southern Aegean Sea region. Geochim. cosmochim. Acta, 53(1):43-57.

The geochemistry of sediments from the southern Aegean Sea demonstrates that the active tectonics in the Hellenic Arc-Trench system favor hydrothermal mineralization processes involving leaching of oceanic crust. The distribution and geochemical behavior of Mn, Fe, Cu, Zn, Pb, and Ba indicate a hydrothermal influence at plate boundaries, in fore-arc basins, and on the island arc. All fore-arc basins have greater Mn enrichments and higher heat flow values than the trenches. Because the Fe-Mn sediments identified are end-members of the hydrothermal fractionation sequence known from areas where leaching of oceanic crust occurs, it is suggested that other members of the sequence, such as metal sulfides, may be found in these areas. Dept. of Geol., Univ. of Patras, Greece.

D170. Historical geology, stratigraphy 89:3851

Bogaard, P,v.d. et al., 1988. Eruption ages and magma supply rates during the Miocene evolution of

Gran Canada. Naturwissenschaften, 75(12):616- 617. Inst. fur Mineral. der Ruhr Univ., D-4630 Bochum, FRG.

89:3852 Carannante, G. et al., 1988. Carbonate Utbofacies as

paleolatitude indicators: problems and limitations. Sedim. Geol, 60(1-4):333-346.

Detailed study of Miocene carbonates in the Medi- terranean region and their modern analogues reveals at least three major lithofacies in addition to the classic tropical coral reef chlorozoan lithofacies: chloralgal lithofacies, similar to the chlorozoan but without hermatypic corals; rhodalgal lithofacies with abundant encrusting coralline algae; and molechfor lithofacies consisting of benthic foraminifers, molluscs, echinoids, bryozoans, and barnacles. These carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature. Chloralgal and rhodalgal lithofacies can be considered transitional between the chlorozoan lithofacies of shallow tropical shelves and the molechfor lithofacies of colder and/or deeper areas. Dept. Sci. della Terra, Univ. di Napoli, Largo S. Marcellino 10, 80138 Naples, Italy.

89:3853 Chaloner, W.G. and L.R.M. Cocks, 1989. [Special

section.] Biota and palaeoatmospheres. [Sympo- sium, London, 19 December 1987.] J. geol. Soc., Loud., 146(1):145-186; 6 papers.

The symposium reached the general consensus that the composition of the atmosphere has changed both since its primordial formation and during the Phanerozoic. Included in this special section are a review of evidence for outgassing, based on the inert gas and isotopic composition of meteorites and terrestrial materials; evidence for significant changes in the oxygen and carbon dioxide in the air in response to photosynthetic activity; the H, C, N, and O cycles which evolved as the abiotic synthesis of organic substrates gave way to 'chemo-organo- trophy' and eventually to photosynthesis; the presence of fossil charcoal in the geologic record from the Devonian which constrains the percent of atmospheric 02 to within 13-35%; the present state of carbon cycling and the complications introduced by other atmospheric constituents relative to a greenhouse effect; and a perspective on paleo- atmospheric variations with particular reference to their ecological implications. (hbf)

89:3854 Clifton, H.E., 1988. Sedimentologic relevance of

convulsive geologic events. Spec. Pap. geol. Soc. Am., 229:1-6.


The role of 'extraordinarily energetic events of regional influence,' such as explosive volcanic eruptions, bolide impacts, giant mass failures, catastrophic floods, major earthquakes, and large storms and tsunamis, is poorly understood, perhaps because in many cases the record of events beyond the pale of history is poorly defined and subject to over- simplification. In particular, if the difficulty of establishing the synchroneity of effects stemming from a single event can be overcome, it is likely that convulsive events will assume greater importance in the overall evaluation of the geologic record. USGS, 3455 Middlefield Rd., Menlo Park, CA 94025, USA. (hbf)

89:3855 Gruszczyflski, Michal et al., 1989. A brachiopod

calcite record of the oceanic carbon and oxygen isotope shifts at the Permian/Triassic transition. Nature, Lond., 337(6202):64-68.

We present here empirical data derived from the brachiopod shell calcite, whose isotope composition generally corresponds to that of the seawater in which the animals lived originally. These data allow us to assess quantitatively the magnitude of changes in the Earth's ecosystem during the critical time of the Permian/Triassic transition. Inst. of Paleobiol., Polish Acad. of Sci., AI. Zwirki i Wigury 93, PL-02-089 Warsaw, Poland.

89:3856 Hay, W.W., 1988. Paleoceanography: a review for the

GSA centennial. Geol. Soc. Am. Bull., 100(12): 1934-1956.

The birth of the multidisciplinary science of paleoceanography occurred roughly 30 yr ago, and much of its rapid progress can be attributed to the coring programs begun after World War II. Paleocean- ography research aims at defining the history of the circulation of the oceans. Significant advances toward this end include development of a refined stratigraphic base with a resolution of about 100,000 yr for much of the Mesozoic; documentation of the thermal history of the ocean from the Mesozoic on; knowledge of the fluctuations and interactions involving the calcium carbonate compensation depth; investigation of organic, carbon-rich deep-sea sediments; the revelation and implications of deep- sea hiatuses; changes in the paleogeography of ocean plankton; and new insights into the changing modes of circulation, which in the deep sea may reverse on a variety of time scales. Coop. Inst. for Res. in Environ. Sci., Univ. of Colorado, Boulder, CO 80309, USA. (hbf)

89:3857 Holser, W.T. et al., 1989. A unique geochemical

record at the Permian/Triassic boundary. Nature, Lond., 337(6202):39-44.

A 330-metre core drilled through the marine Per- mian/Triassic boundary in the Carnic Alps of Austria allows closely-correlated studies of geochemistry, petrography and palaeontology across the boundary. The isotope shifts and metal concentrations are extended, multiple and complex, and do not resemble those seen at the Cretaceous/Tertiary boundary. Both the carbon isotope shifts and chemical events (including an iridium anomaly) may have causes related to a major regression of the sea. Dept. of Geol. Sci., Univ. of Oregon, Eugene, OR 97403, USA.

89:3858 Hudson, J.D., 1989. Palaeoatmospheres in the Phan-

erozoic. J. geol. Soc., Lond., 146(1):155-160.

The likely controls on atmospheric composition are reviewed and the role of organisms stressed as monitors, recorders, motors and moderators of palaeoatmospheric changes. Whereas there is a good general case for changes in p02 and pCO 2 during Phanerozoic time, proposals for timing and mechanism in the earlier Phaneroxoic are speculative at present. It seems probable that the Late Paleozoic spread of land plants raised 02 and reduced CO 2 levels in the atmosphere. The end-Cretaceous crisis had a transient impact on the atmosphere, whose general constancy through geological time is one of the most remarkable features of Earth history. Dept. of Geol., Univ. of Leicester, LE1 7RH, UK.

89:3859 Ivanova, Ye.V., 1987. Miocene climatic zonation of

the Indian Ocean. Oceanology (a translation of Okeanologiia), 27(6):719-724.

The locations of climatic zones at four time intervals during the Miocene are reconstructed from the ranges of planktic Foraminifera shells in Indian Ocean Miocene deposits. A gradual cooling in the south during the Miocene, as a result of growth of the Antarctic glacial shield, was accompanied by migration of climatic zones toward the Equator. Two warmer intervals (end of the Early and Late Miocene) and two cooler periods (beginning of the Early Miocene and end of the Middle Miocene) are identified in the north. The climate of the Indian Ocean was warmer throughout the Miocene and the climatic zones were located farther to the south than at present. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.


89:3860 Kallel, Nejib et al., 1988. Evidence of cooling during

the Younger Dryas in the western North Pacific. Oceanologica Acta, 11(4):369-375.

The isotopic and micropaleontological records from a western North Pacific sediment core show a definite cooling synchronous with the Younger Dryas, as recorded in the North Atlantic. The deglaciation began at ~14,750 yrBP and the polar front retreat started at ~ 12,750 yrBP. It reached its northernmost position, during this period, at

11,450 yrBP. Between about 11,000 and 10,000 yrBP, the polar front occupied a more southerly location. Centre des Faibles Radioactivites, Lab. mixte, ave. de la Terrasse, 911198 Gif-sur-Yvette Cedex, France.

89:3861 Medvedev, V.S. and Yu.A. Pavlidis, 1987. New

geological-geomorpbological data on the shelf areas of the Seychelles Islands and Madagascar. Oceanology (a translation of Okeanologiia), 27(6):729-734. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR.

89:3862 Mobley, C.M., 1988. Holocene sea levels in southeast

Alaska: preliminary results. A retie, 41 (4): 261-266. Sheldon Jackson Coll., 801 Lincoln St., Sitka, AK 99835, USA.

89:3863 Turner, G., 1989. The outgassing history of the

Earth's atmosphere. J. geol. Soc., Lond., 146(1): 147-154.

Helium provides the best indication of current noble-gas outgassing rates, which are extremely low in comparison to the mean rates over geological time. Extremely high (4°Ar/36Ar) ratios in MORB indicate conclusively that the major release of primordial volatiles occurred before there had been significant growth of radiogenic 4°At in the mantle, i.e. within the first 500 Ma or so of Earth history. High (ngXe/]3°Xe) ratios in MORB combined with the argon data can be used to indicate that 80% or more of the release occurred in the first 50 Ma of Earth history, though alternative interpretations are possible. The data can be used to constrain a narrow range of acceptable mathematical models. Dept. of Geol., Univ. of Manchester, M13 9PL, UK.

89:3864 von Haugwitz, Wolfram and H.K. Wong, 1988. The

Dogger Bank: seismic stratigraphy and Holocene sedimentation. Mitt. geol.-paldont. Inst. Univ. Hamb., 65:381-407. Geol.-Palaeontol. Inst. und

Mus. der Univ. Hamburg, Bundestr. 55, D-2000 Hamburg 13, FRG.

89:3865 Williams, G.E., 1989. Precambrian tidal sedimentary

cycles and Earth's paleorotation. Eos, 70(3):33, 40-41.

Paleotidal cycles ranging from semidiurnal to the lunar nodal cycle apparently are recorded by Late Precambrian (~650 Ma) rhythmically laminated sedimentary rocks (rhythmites) of postulated ebb- tidal origin in South Australia. The rhythmites may provide unique information on paleotidal periods and Earth's paleorotation. Calculated values suggest that since Late Precambrian time the average equivalent phase lag (the angle between the Earth- Moon axis and Earth's tidal bulge, derived from the response of the solid and ocean tides) was near 3 ° rather than the present value of 6 °. Precambrian sedimentary rhythmites may record much valuable information on the early history of Earth's rotation and the lunar orbit. Dept. of Geol. and Geophys., Univ. of Adelaide, South Australia.

89:3866 Xue, Chunting, Guodong Cheng and Yongqing

Zhou, 1988. Relationship between late Late Pleistocene and early Early Holocene terrestrial deposits and sea level changes in Yellow River Delta area. Mar. Geol. Quat. Geol., 8(2): 103-11 I. (In Chinese, English abstract.) Inst. of Mar. Geol., Ministry of Geol. and Min. Res., Qingdao, People's Republic of China.

89:3867 Zachos, J.C., M.A. Arthur and W.E. Dean, 1989.

Geochemical evidence for suppression of pelagic marine productivity at the Cretaceous/Tertiary boundary. Nature, Lond., 337(6202):61-64.

Stable isotope data from planktonic and benthic microfossils across the K / T boundary in the North Pacific reveal a rapid and complete breakdown in this biologically mediated gradient. The fluxes of barium and CaCO 3 also decrease significantly at the time of the major marine plankton extinctions. The implied substantial reduction in oceanic primary productivity persisted for ~0.5 Myr before the carbon isotope gradient was gradually re-established. The stable isotope and preservational data indicate that environmental change, including cooling, began at least 200 kyr before the K / T boundary, and a peak warming of ~ 3 ° C occurred 600 kyr after the boundary event. Grad. Sch. of Oceanogr., Univ. of Rhode Island, Narragansett, RI 02882, USA.


DI80. Paleontology (see also E-BIOLOGICAL OCEANOGRAPHY)

89:3868 Abelmann, Andrea, 1988. Freeze-drying simplifies

the preparation of microfossils. Micropaleontol- ogy, 34(4):p.361. Alfred Wegener Inst. fur Polar- und Meeres., Postfach 12061, Columbusstrasse, D-2850 Bremerhaven, FRG.

89:3869 Allison, P.A., 1988. Konservat-Lagerst~tten: cause

and classification. Paleobiology, 14(4):331-344.

A review of the processes required for exceptional preservation of soft-bodied fossils demonstrates that anoxia does not significantly inhibit decay and emphasizes the importance of early diagenetic mineralization. Early diagenesis is the principal factor amongst the complex processes leading to soft-part preservation. The development of a particular preservational mineral is controlled by rate of burial, amount of organic detritus, and salinity. A new causative classification of soft-bodied fossil biotas is presented based upon fossil mineralogy and mineral paragenesis. Univ. of Washington, Friday Harbor Lab., 620 University Rd., Friday Harbor, WA 98250, USA.

89:3870 Berggren, W.A. and K.G. Miller, 1988. Paleogene

tropical planktonic foraminiferal biostratigraphy and magnetobiochronology. Micropaleontology, 34(4):362-380.

Confusion has arisen over the connotation and correlation of two competing tropical-subtropical Paleogene planktonic foraminiferal zonations (Berggren 1969, Blow 1979). This derives from the fact that the former scheme, when originally published, was viewed as provisional and precise definitions were not given for the zonal system. We review here the development of these two zonal schemes in a historical context, present a definition, in part revised and updated, of the P-zonation system of Berggren (1969), and correlate this and related zonal schemes to a magnetostratigraphic and, ultimately, magnetobiochronologic framework to the extent possible. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA.

89:3871 Boltovskoy, Demetrio and Ana Vrba, 1988. Clas-

sification and geographic distribution of Sty- iodictya-type radiolarians. Micropaleontology, 34(4):332-340. Dept. de Ciencias Biol., Univ. de Buenos Aires, 1428 Buenos Aires, Argentina.

89:3872 Boltovskoy, Esteban and Demetrio Boltovskoy,

1988. Cenozoic deep-sea benthic Foraminifera: faunal turnovers and paleobiogeographic differences. Revue Micropalbont., 31(2):67-84.

A study of the Foraminifera from DSDP sites 208, 289, 305, 357, 360 and 369 shows that Oligocene and post-Oligocene faunas differ little from Recent assemblages, this entire interval being characterized by slow and gradual faunal replacements: the most important faunal turnover recorded took place below the Eocene-Oligocene boundary. Within the Oligocene-Pliocene interval, most of the changes defined are not correlated between sites; the makeup and relative proportions of assemblages are more influenced by geographic location and ecological factors than by their evolutionary history. The usefulness of deep-sea benthic Foraminifera for biostratigraphic interpretations is restricted by their spotty occurrence, their long time-ranges, and their markedly local qualitative and quantitative character and variations. Museo Argentino de Cienc. Nat. Bernardino Bivadavia, Av. Angel Gallardo 470, 1405 Buenos Aires, Argentina.

89:3873 Hoffman, Antoni, 1989. Mass extinctions: the view of

a sceptic. J. geol. Soc., Lond., 146(1):21-35.

The concept of periodic mass extinctions by extraterrestrial impacts has contributed very strongly to the current revival of interest in the problem of mass extinctions. In this context, several radical claims have been made. The validity of these claims, however, is questionable at all levels: from the interpretation of particular events, to the concept of mass extinctions as a special class of phenomena, to their proposed causation by impacts. Mass extinctions may actually be clusters of more or less accidentally aggregated-in-time but causally distinct extinction episodes. Inst. of Paleobiol., Acad. of Sci., Al. Zwirki i Wigury 93, PL-02-089 Warsaw, Poland.

89:3874 Kamiya, Takahiro, 1988. Contrasting population

ecology of two species of Loxoconcha (Ostracoda, Crustacea) in Recent Zostera (eelgrass) beds: adaptive differences between phytal and bottom- dwelling species. Micropaleontology, 34(4):316- 331.

The population density of the phytal species Loxo- concha japonica increased explosively in early sum- mer and suddenly decreased in late autumn, characteristics closely related to seasonal changes in the Zostera stock. Conversely, the bottom-dwelling L. uranouchiensis had a population density relatively


constant through the year; its main breeding season was from autumn through winter. Some ecological features, such as the main breeding season and fecundity are preserved in sub-fossil population structure, which will help in paleoecological reconstructions and in understanding fossil paleocom- munities. Dept. of Earth Sci., Kanazawa Univ., l-l, Marunouchi, Kanazawa 920, Japan.

89:3875 Miller, A.I. and J.J. Sepkoski Jr., 1988. Modeling

bivalve diversification: the effect of interaction on a macroevolntionary system. Paleobiology, 14(4): 364-369.

The global diversification of Bivalvia has historically received two conflicting interpretations. One is that a major upturn in diversification was a consequence of Late Permian mass extinction. The other is that the bivalves have experienced slow but nearly steady exponential diversification through most of their history, unaffected by interactions with other clades. Through most of the Phanerozoic the diversity of bivalves did indeed exhibit slow growth. However, 'hyperexponential bursts' in diversification during the initial Ordovician radiation and after the Late Permian and Late Cretaceous mass extinctions suggest that a higher diversification rate was damp- ened through most of the Phanerozoic. Analysis of the observed pattern using a two-phase coupled logistic model suggests that interactions with other taxa have substantially affected bivalve global diversity. Dept. of Geol., Univ. of Cincinnati, OH 45221, USA.

89:3876 Moore, P.D., 1989. Some ecological implications of

palaeoatmnspheric variations. J. geoL Soc., Lond., 146(1):183-186.

A graphic model is presented to indicate the complexity of interacting forces resulting from a change in atmospheric carbon dioxide level, and it can be seen that any resultant ecological outcome will be influenced by a series of factors. This is particularly true of the hydrological consequences of atmospheric change. Changes in the levels of both atmospheric carbon dioxide and oxygen have had profound effects on the evolution of plant life by modifying the selective pressures favoring alternative systems of carbon assimilation. These photosynthetic strategies are also closely related to local hydrology. Div. of Biosphere Sci., King's Coll., Campden Hill Rd., London W8 7AH, UK.

89:3877 Nigrini, Catherine and J.P. Caulet, 1988. The genus

Anthocyrtidlum (Radiolaria) from the tropical Late Ncogene of the Indian and Pacific oceans. Micropaleontology, 34(4):341-360.

Detailed morphologies of ten species (two new) along with their geographic and stratigraphic ranges are described. Phylogenetic lineages may be proposed in some cases, but in general our studies have not revealed clear evolutionary trends. However, eight stratigraphically useful and easily recognizable Neogene datum levels based on Anthocyrtidium can be identified and paleomagnetically dated. 510 Papyrus Dr., La Habra Heights, CA 90631, USA.

89:3878 Nirei, Takashi and Takeshi Sato, 1988. Fossil pollen

assemblages of the core sample from Tobishima Basin, central Japan Sea. J. Fac. mar. Sci. Technol., Tokai Univ., 26:27-37. (In Japanese, English abstract.)

89:3879 Rosen, B.R., 1988. Progress, problems and patterns in

the biogeography of reef corals and other tropical marine organisms. Helgol~mder Meeresunters., 42(2):269-301.

The first part of this paper summarizes the descrip- tive biogeography of reef corals, with mention of other tropical marine organisms, in terms of present-day latitudinal and longitudinal patterns, and stratigraphical patterns (mostly Cenozoic). The second part reviews current theories for explaining the distribution of reef corals. Dept. of Palaeont., Brit. Mus., Cromwell Rd., London SW7 5BD, UK.

89:3880 Russell, M.P. and D.R. Lindberg, 1988. Real and

random patterns associated with molluscan spatial and temporal distributions. Paleobiology, 14(4): 322-330.

The species-level properties of geographic range and geologic duration are often used as variables in evolutionary studies. However, estimates of species duration are not independent of estimates of geographic range. Before these properties are used in macroevolutionary hypotheses, error associated with these estimates must be quantified. To assess the error associated with estimates of geographic range and geologic duration, various sampling regimes were modeled and the bias associated with the


estimates was calculated. Three analyses are presented which document this bias. Dept. of Paleontol., Univ. of Calif., Berkeley, CA 94720, USA.

89:3881 Sepkoski, J.J. Jr., 1989. Periodicity in extinction and

the problem of cataslrophism in the history of life. J. geol. Soc., Lond., 146(1):7-19.

The hypothesis that extinction events have recurred periodically is greatly strengthened by new data on the stratigraphic ranges of marine animal genera. In the interval from the Permian to Recent, these data encompass some 13,000 generic extinctions, pro- viding a more sensitive indicator of species-level extinctions than previously used familial data. Extinction time series display nine strong peaks spaced at 26 Ma intervals. These new data weaken or negate most arguments against periodicity, which have involved criticisms of the taxonomic data base, sampling intervals, chronometric time scales, and statistical methods used in previous analyses. The new data also suggest that many of the periodic events may not have been catastrophic, occurring instead over several stratigraphic stages or substages. Dept. of Geophys. Sci., Univ. of Chicago, 5734 S. Ellis Ave., Chicago, IL 60637, USA.

89:3882 Sliter, W.V., 1989. Biostratigraphic zonation for

Cretaceous planktonic foraminifers examined in thin section. J. foram. Res., 19(I):I-19.

A biostratigraphic zonation for Cretaceous planktonic foraminifers examined in thin section provides improved resolution for dating oceanic pelagic limestones as well as calcareous concretions in continental margin deposits. The zonation comprises 31 zones and 4 subzones that span the Hauterivian to Maestrichtian stages, and are modified from previous zones based on isolated specimens. Use of the zonation has allowed dating and detailed correlation of allochthonous pelagic limestone in several circum-Pacific tectonostratigraphic terranes. The zonation also provides a framework for corre- lating oceanic and continental-margin deposits as well as low- and middle-latitude assemblages of Cretaceous planktonic foraminifers. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA.

89:3883 Wei, Wuchang and S.W. Wise Jr., 1989. Discouster

praeb/fax n.sp.: a possible ancestor of Discoaster b/fax Bukry (Coccolithophoridae). J. Paleont., 63(1): 10-14. Dept. of Geol., Florida State Univ., Tallahassee, FL 32306, USA.

D200. Gravity, geodesy, magnetism

89:3884 Brandsma, Dan, S.P. Lund and T.L. Henyey, 1989.

Paleomagnetism of Late Quaternary marine sediments from Santa Catalina Basin, California continental borderland. J. geophys. Res., 94(B 1): 547-564.

Paleomagnetic secular variation (PSV) records from three Santa Catalina Basin sediment cores permit a correlation of the cores and four independent PSV calibration curves from western North America that have detailed radiocarbon age control. The PSV correlations indicate that the sediments are all younger than ~ 11,000 yrBP. The relative accuracy of the curves is ~200 yrs, an order-of-magnitude improvement in the chronology of these sediments. Sedimentation rates derived from the curves indicate a constant rate of 20-25 cm/kyr for the last 6700 yr throughout the basin, and more variable rates prior to 6700 yrBP. The change in rate corresponds to a subtle change in lithology and probably indicates a major shift in paleoceanographic processes within the basin at 6700 yrBP. Dept. of Geol. Sci., Univ. of So. California, Los Angeles, CA 90089-0740, USA.

89:3885 Segall, P. and M.V. Matthews, 1988. Displacement

calculations from geodetic data and the testing of geophysical deformation models. J. geophys. Res., 93(B 12): 14,954-14,966.

Solution by constrained optimization, its connection with generalized matrix inverses, and currently used solution methods are reviewed, and a 'model coor- dinate' solution is introduced that fixes the inde- terminate components of the displacement field by minimizing the difference between computed dis- placements and those predicted by a geophysical model. A means to exploit overdetermination of some geodetic data by decomposing model residuals from a geometrically redundant network into two orthogonal components is also proposed. USGS, 345 Middlefield Rd., MS/977, Menlo Park, CA 94025, USA.

D210. Heat flow 89:3886

Denlinger, R.P. and W.Z. Savage, 1989. Thermal stresses due to cooling of a viscoelastic oceanic lithosphere. J. geophys. Res., 94(B1):744-752.

As the lithosphere cools, the horizontal components of the contraction give rise to potentially large


thermal stresses. Instant-freezing methods to cal- culate these stresses inaccurately predict transient thermal stresses in rapidly cooling silicate glass plates because of the temperature dependent rhe- ology of the material. For this reason a thermoviscoelastic model is used to estimate thermal stresses in young oceanic lithosphere, and a theory is formulated for linear creep processes that have an Arrhenius rate dependence on temperature. Stress differences between instant-freezing and linear- thermoviscoelastic theory are more pronounced at early times (0-20 m.y.) when the instant-freezing stresses may be twice as large; both methods underestimate the depth of compressi~qal stresses. School of Oceanogr., Univ. of Washington, Seattle, WA 98195, USA.

89:3887 Henry, S.G. and H.N. Pollack, 1988. Terrestrial heat

flow above the Andean subduction zone in Bolivia and Peru. J. geophys. Res., 93(B12):15,153- 15,162.

Thirty-five new and nine revised heat flow measurements are reported for sites overlying the Andean subduction zone in Bolivia and Peru. Sites in the Peruvian Cordillera have a mean heat flow of 41 mW m 2, whereas those in the Bolivian Cordillera and Altiplano average 84 mW m 2, and sub-Andean ranges and adjacent sedimentary platform have a mean flow of 50 mW m 2. The higher heat flow lies east of Quaternary volcanoes along the Bolivia- Chile border and can be recognized as a 'backarc' heat flow high. Contrasting flow patterns correlate with the variable angle of subduction of the Nazca Plate beneath the region. The presence of extensive Miocene volcanics in Peru suggest that Peruvian heat flow at 10 Ma was similar to that in Bolivia today. Imbrication of cold oceanic lithosphere beneath Peru may provide a mechanism for rapid reduction of the heat flow over the past 10 Ma. Conoco Inc., P.O. Box 2197, Houston, TX 77252, USA.

D240. Local or regional tectonics

89:3888 Breen, N.A., 1989. Structural effect of Magdalena

Fan deposition on the northern Colombia convergent margin. Geology, geol. Soc. Am., 17(1): 34-37.

A mechanism is proposed which explains the curvature of structural trends in some mountain belts as the result of rapid sedimentary loading on the upper plate within a subduction zone, causing an

indentation of the plate, reducing its surface slope, and inhibiting sliding on the plate interface. Sedi- ments beneath the less-than-critical slope will de- form internally, and over time can produce a marked effect on the geometry of the mountain belt. The Magdalena Fan on the northern Colombia margin provides an example of the proposed mechanism. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA. (hbf)

89:3889 Dewey, J.F. et al., 1988. The tectonic evolution of the

Tibetan Plateau. Phil. Trans. R. Soc., 327(1594): 379-413.

The Tibetan Plateau between the Kunlun Shin and Himalayas consists of terranes accreted successively to Eurasia between the Late Permian and Middle Eocene, when peninsular India was added to the plateau. Substantial southward ophiolite obduction occurred in the Late Jurassic and latest Cretaceous- earliest Paleocene. Paleomagnetic data suggest suc- cessive wide Paleotethyan oceans during the Late Paleozoic and Early Mesozoic and a Neotethys, at least 6000 km wide, during the Mid-Cretaceous. Thickening of the Tibetan crust occurred by northward-migrating north-south shortening and vertical stretching during the Mid-Eocene to earliest Mio- cene identation of Asia by India. From Early Pliocene to the present, the plateau has risen about two km and has suffered east-west extension. Dept. of Earth Sci., Parks Rd., Oxford OXI 3PR, UK.

89:3890 Faure, M., P. Moni6 and O. Fabbri, 1988. Micro-

tectonics and 39Ar-4°Ar dating of high pressure metamorphic rocks of the south Ryukyu Arc and their bearings on the pre-Eocene geodynamic evolution of eastern Asia. Tectonophysics, 156(1- 2): 133-143.

The pre-Eocene metamorphic rocks found in the Yaeyama Islands (southern Ryukyu Arc) have disputed relationships with the metamorphic formations of Japan and Taiwan. New stratigraphic, microstructural, and 39Ar-a°Ar data on the pre- Eocene formations of the islands are presented which support the correlation of the high-pressure schists with the Permian Sangun schists. The relationships with the other formations of the arc, southwestern Japan, and Taiwan are discussed, and the pre-Miocene geologic evolution of the south Ryukyu Arc is integrated into already proposed geodynamic models for southwestern Japan. Dept. des Sci. de la Terre, Univ. d'Orleans, 45067 Orleans Cedex 2, France.


89:3891 Faure, Michel, Olivier Fabbri and Patrick Monie,

1988. The Miocene bending of southwest Japan: new 39Ar/4°Ar and microtectonic constraints from the Nagasaki schists (western Kyushu), an extension of the Sanbagawa high-pressure belt. Earth planet. Sci. Letts, 91(1-2): 105-116. Dept. des Sci. de la Terre, Univ. d'Orleans, Orleans, France.

89:3892 Karsten, J.L. and J.R. Delaney, 1989. Hot spot-ridge

crest convergence in the northeast Pacific. J. geophys. Res., 94(B1):700-712.

Evolution of the Juan de Fuca Ridge during the past 7 m.y. has been reconstructed taking into account the propagating rift history and migration of the spreading center in the 'absolute' (fixed hot spot) reference frame. Northwestward migration of the spreading center has resulted in progressive en- croachment of the ridge axis on the Cobb Hot Spot and westward jumping of the central third of the ridge axis more recently than 0.5 Ma. Relative seamount volumes also indicate variation in magmatic output during this interval; in most cases rift propagation has been away from the hot spot. No obvious correlation exists between propagation rate and increasing hot spot output or increasing prox- imity to the ridge axis. These observations do not support the concept of hot spot-driven rift propagation; however, short-term reversals in propagation direction at the Cobb Offset coincide with activity of the Heckle melting anomaly, suggesting that local propagation effects may be related to excess magma supply at the ridge axis. Inst. of Geophys., Univ. of Hawaii, 2525 Correa Rd., Honolulu, HI 96822, USA.

89:3893 Lonsdale, Peter, 1989. The rise flank trails left by

migrating offsets of the equatorial East Pacific Rise axis. J. geophys. Res., 94(B1):713-743.

Seabeam and magnetic surveys of the young rise flank around nontransform rise crest offsets at 5.5°N, 4.9°N, 3.4°N, 2.0°N, and 2.8°S mapped distinctive trails of obliquely lineated, highly magnetic crust that spreads from curving, overlapping rift zones. Patches of interrift crust are periodically shed from the axial zone, together with abandoned portions of overlapped rift zone, to become important elements of the rise flank trails. The oblique azimuths of the paired 'fracture zone' trails that diverge from the rise crest offsets show that most have migrated along the rise crest at average speeds of 25-125 mm/yr. Most offsets on the southern Pacific-Cocos boundary have migrated south, and most on the northern boundary have migrated north; the patterns are not readily explained by the

inferred distribution of mantle upwellings along the EPR axis. Scripps Inst. of Oceanogr., La Jolla, CA 92093, USA.

89:3894 McCaffrey, Robert, 1988. Active tectonics of the

eastern Sunda and Banda arcs. J. geophys. Res., 93(B12): 15,163-15,182.

The tectonics of the eastern Sunda and Banda arcs of eastern Indonesia are inferred from centroid depths, seismic moments, and fault plane solutions of 63 large earthquakes that occurred between 1962 and 1984. The collision of Australia with the Banda Arc shortens the upper plate beneath the forearc and backarc basin between the Timor and Scram troughs. The eastern end of the Sunda Arc and southern Banda Arc respond to collision by shortening in the direction of convergence, elongating perpendicular to convergence, and thrusting over the backarc basin. The rate of N-S shortening over the entire upper plate is roughly 20% of the predicted convergence rate between Australia and southeast Asia. The Indonesian example demonstrates the complexity in three dimensions of continental accretion and mountain building by arc-continent collision. Dept. of Geol., Rensselaer Polytech. Inst., Troy, NY 12180, USA.

89:3895 McCann, W.R. and R.E. Habermann, 1989. Mor-

phologic and geologic effects of the subduction of bathymetric highs. Pure appl. Geophys., 129(1- 2):41-69.

Observations on forearc morphology and geology indicate that both relief on the subducting seafloor and rate of sediment supply to the subduction zone are important factors for the evolution of forearc features. An increase in either factor tends to compress the plate, thrusting sediments landward, and perhaps deforming the sediments and crystalline rocks of the overriding plate, as well as producing coastal uplift. The more buoyant features produce the more marked changes and may lead to significant erosion of the upper plate and subsidence of its leading edge within a period of a few million years. Dept. of Geol., Univ. of Puerto Rico, Mayaguez, Puerto Rico 00708, USA. (hbf)

89:3896 Murata, Akihiro, 1987. Hokusatsu Bend and clock-

wise rotation of the southwest Japan Arc. J. Fac. Sci. Univ. Tokyo, (2)21(4):333-349.

Detailed mapping and geometrical analysis of the Shimanto and Sambosan groups, which have been folded and faulted at the Hokusatsu Bend between


the Southwest Japan Arc and Nansei Shoto Arc, reveal that the folds within the bend are conical and have more steeply dipping axes (~30°WNW) than those in the other bends in Kyushu. The bends appear to have formed in the Miocene as the northeast limb of the arc rotated clockwise ~ 3 0 ° and its southern counterpart rotated 300-40 ° coun- terclockwise. Geol. Inst., Faculty of Sci., Univ. of Tokyo, 113, Japan. (hbf)

89:3897 Mutter, J.C. and R.L. Larson (and the northwest

Australia study group), 1989. Extension of the Exmouth Plateau, offshore northwestern Austra- lia: deep seismic reflection/refraction evidence for simple and pure shear mechanisms. Geology, geol. Soc. Am., 17(1):15-18.

Results of a two-ship reflection and refraction program to determine the velocity structure of the deep crust and upper mantle beneath the Exmouth Plateau, supplemented by dredging and exploratory drilling data, reveal that the plateau is underlain by large rotated blocks bounded by deep, normal faults. Magmatic underplating is present on the outer plateau, but absent in the central region. It is proposed that initial deformation consisted of simple shear detachments along low-angle faults in the central plateau, which subsequently passed laterally into an outer region of pure shear deformation, distinguished by high-angle normal faults, and magmatism. Lamont-Doherty Geol. Observ., Pali- sades, NY 10964-0190, USA. (hbf)

89:3898 Smith, E.G.C., Tim Stern and Martin Reyners, 1989.

Subduction and back-arc activity at the Hikurangi convergent margin, New Zealand. Pure appl. Geophys., 129(1-2):203-231.

The Hikurangi margin is a zone of oblique subduction extending from the Kermadec Trench to ~42°S along the Pacific-Australian plate boundary. Sub- duction here has been occurring for at least 16-20 Ma at a rate which varies from ~ 6 0 mm/a at its southern end to ~45 mm/a at 42°S. North of 39°S there has been andesitic volcanism for 18 Ma, and backarc extension for 4 Ma has created an onshore basin with high heat flow, thin crust, and low upper mantle velocities; the evidence implies that the plate interface is uncoupled. South of 39°S volcanism is absent and downward flexure linked to strong coupling has produced a backarc basin with normal heat flow. It is postulated that these marked differences between north and south may be the result of a NE-SW increase in the buoyancy of the Pacific lithosphere. Geophys. Div., Dept. of Sci. and Indust. Res., Wellington, New Zealand. (hbf)

89:3899 Sorel, Denis et al., 1988. The role of slab-pnil force in

the Plioeene--Pleistoeene geodynamic evolution of the Aegean Arc: subsidence and uplift of the external arc and changes in the tectonic regime. C. r. Acad. Sci., Paris, (S6r. II)307(19):1981- 1986. (In French, English summary.) Lab. de Geol. dynam, interne, Bat. no. 509, Univ. Paris XI, Centre univ., 91405 Orsay Cedex, France.

89:3900 Versfelt, J. and B.R. Rosendahl, 1989. Relationships

between pre-rift structure and rift architecture in lakes Tanganylka and Malawi, East Africa. Nature, Lond., 337(6205):354-357.

In the same way that tensile cracks in the side of a brick building generally follow the mortar between bricks, rifts initially follow the weakest pathways in the pre-rift materials. In the Tanganyika and Malawi Rift Zone region, the rift system follows Proterozoic mobile belts and bifurcates around the Tanganyika craton, which apparently has acted as a resistant core. Here we show that the fundamental architecture of the Tanganyika and Malawi Rift Zones (that is, the positioning of half-grabens, the way they link together, and the types and trends of linking structures) is strongly influenced by the nature of the pre-rift fabric and the orientation of the stress field. Texaco, Latin America/West Africa, P.O. Box 343300, Coral Gables, FL 33134, USA.

89:3901 Yin, Yanhong, 1988. The origin of the Manila

Trench. Mar. Geol. Quat. Geol., 8(2):37-45. (In Chinese, English abstract.)

The 1000-km-long Manila Trench, west of Luzon in the eastern South China Sea, is an arcuate structure, striking S-N and facing west. Seismic data indicate the active Benioff zone beneath the trench lies at a depth of 200 km and dips 40-50°E. The trench is oriented perpendicular to the South China Sea Basin, where spreading ceased at 17 Ma. Data suggest that the trench formed in response to the obduction of the Luzon microplate toward the South China Sea crust and that the Central Cordillera mountain on Luzon, which is rootless although 3000-m high, is supported by the pushing of the Philippine Sea Plate. Inst. of Mar. Geol., Min. of Geol. and Mineral Resour., Qingdao, People's Republic of China. (hbf)

89:3902 Yu, H.-S., 1988. Tectonic evolution of the Pearl River

Mouth Basin off the South China coast. Acta oceanogr, taiwan., 20:79-94.


Multichannel seismic profiles, exploratory well data, and the regional geology of South China suggest a backarc spreading model for the tectonic development of the 150,000 km 2 Pearl River Mouth Basin. From Mid-Jurassic to Mid-Cretaceous, the South China margin was subjected to regional uplift, granitic intrusions, and basaltic eruptions marking the subduction of the Kula Plate. From Late Cretaceous to Mid-Oligocene, the basin was dominated by rifting of attenuated continental crust which ruptured segments of the basins. A prominent Early Miocene unconformity separates tilted non- marine to marginal-marine Lower Tertiary facies deposited in grabens, from overlying undisturbed marine Neogene facies. Eruptions of Cenozoic basalt may have interrupted the drifting stage of backarc spreading. Inst. of Oceanogr., Natl. Taiwan Univ., Taipei, Taiwan.

89:3903 Zhang, Kang, 1988. Cenozoic extension in the

eastern Asia and its gcotectonic significance. Mar. Geol. Quat. Geol., 8(3):25-34. (In Chinese, Eng- lish abstract.) Inst. of Petroleum Geol., Min. of Geol. and Mineral Resour., Beijing, People's Republic of China.

D250. Plate and global tectonics

89:3904 Cloetingh, Sierd, Rinus Wortel and N.J. Vlaar, 1989.

On the initiation of subdnction zones. Pure appl. Geophys., 129(1-2):7-25.

An analysis of intraplate stress fields and lithospheric theology to identify possible mechanisms for the formation of subduction zones along passive margins, concludes that aging of such margins will not result in the spontaneous initiation of subduction, and instead favors the action of external plate-tectonic forces acting upon young margins prestressed by thick sedimentary loads, such as might occur in very young oceanic lithosphere. The analysis also suggests that plate reorganizations result from the development of new spreading ridges. Dept. of Sedimentary Geol., Free Univ., P.O. Box 7161, 1007 MC Amsterdam, Netherlands. (hbf)

89:3905 Dewey, J.F., 1988. Extensional collapse of orogens.

Tectonics, 7(6): 1123-1139. (In Chinese, English abstract.)

Lithospheric extension occurs along orogenic belts because they have thicker continental crust, contain structural inhomogeneities, and suffer extensional

orogenic collapse caused by body forces resulting from isostatically compensated elevation gradients. Collapse occurs especially where rapid advective thinning of the shortened thermal boundary con- duction layer occurs beneath an orogen and causes rapid uplift. The extensional collapse of orogens offers a partial explanation for why oceans close and reopen in roughly the same places, preservation of very high pressure metamorphic rocks, and the return of orogenic large crustal thickness to normal without very much erosional denudation of supra- crustal sequences, high-temperature metamorphic assemblages and minimum-melting granitic suites. Dept. of Earth Sci., Parks Rd., Oxford, OXl 3PR, UK.

89:3906 Ernst, W.G., 1988. Tectonic history of subduction

zones inferred from retrograde blueschist P-T paths. Geology, geol. Soc. Am., 16(12): 1081-1084.

Experimental evidence equates the formation of blueschists with the high pressure/temperature re- lations common to subduction zones and related convergent plate settings. However, in many cases, such as in the western Alps, Phanerozoic blueschists bear the intense overprint of later, lower pressure greenschists or epidote-amphibolite facies. It is speculated that such overprints occur when a tectonically-induced halt or marked reduction in plate-closure velocity results in the lower pressure/temperature facies which is associated with upthrusting or diapiric ascent. However, if the blueschist belt returns slowly toward the surface due to isostatic forces during continued plate descent and refrigeration, the low pressure overprint on the schists is lacking. Inst. of Geophys. and Planet. Phys., Univ. of Calif., Los Angeles, CA 90024-1567, USA. (hbf)

89:3907 Hansen, V.L., 1988. A model for terrane accretion:

Yukon-Tanana and Slide Mountain terranes, northwest North America. Tectonics, 7(6): 1167- 1177.

A model is presented which correlates the Yukon- Tanana (YT) and Slide Mountain (SM) terranes within a unifying tectonic framework in which each terrane represents a different crustal level of the same Late Paleozoic-Early Mesozoic magmatic arc and west-dipping subduction complex formed during plate convergence outboard of western North America. The SM represents the upper crustal level of the arc and accretionary complex, and the heterogeneously metamorphosed and ductilely deformed YT represents the deeper crustal level. It is suggested that the YT-Teslin suture zone-SM


association in Yukon may serve as a model for tectonically coherent continental margin expansions. Dept. of Geol. Sci., Southern Methodist Univ., Dallas, TX 75275, USA.

89:3908 Hawkesworth, Chris and Rob Ellam, 1989. Chemical

fluxes and wedge replenishment rates along recent destructive plate margins. Geology, geol. Soc. Am., 17(1):46-49.

Data on the Nd, Sr, and other isotope variations found in island-arc tholeiites lead to the conclusion that the isotope and trace element content of subduction-related basalts and continental plate margins are consistent with a flux from subducted oceanic crust to the mantle wedge. Observed differences can be accounted for by variations in the mantle wedge, rather than in the subducting slab. A model is proposed in which only 25% of Sr and < 15% of the Rb, Ba, and K is derived from the slab, whereas some previously proposed models have postulated that 90% of the K in new crust is slab-derived. The fact that as little as 3% Sr in subducted crust is required for the slab-derived flux implies recycling of most of the large ion lithophile elements deep within the upper mantle. Dept. of Earth Sci., The Open Univ., Milton Keynes MK7 6AA, UK. (hbf)

89:3909 Lin, Jian and E.M. Parmentier, 1989. Mechanisms of

lithospheric extension at mid-ocean ridges. Geophys. J., 96(1): 1-22.

Finite difference and boundary element methods are used to determine steady-state mantle temperatures and velocities which have relevance for the thermal structure of the oceanic lithosphere. The effects of crustal hydrothermal cooling on ridge thermal structure are also examined, and thermal models of ridges are developed which include the effects of lithospheric thickening on mantle flow, the heat of magmatic crustal accretion, and hydrothermal cooling due to seawater. An investigation of gravity and topography within three segments of the EPR demonstrates the importance of spreading rate on ridge thermal and mechanical structure. Dept. of Geol. and Geophys., WHOI, Woods Hole, MA 02543, USA. (hbf)

89:3910 Ocean Drilling Program, (Leg 122 shipboard

scientific party), Ulrich yon Rad and B.U. Haq (co-chief scientists), 1989. Ocean Drilling Pro- gram. Breakup of Gondwanaland. Report. Na- ture, Lond., 337(6204):209-210.

ODP Leg 122 across the old Gondwanan passive margin off northwestern Australia included six drill sites into the > 8 km of sediment covering subsided continental crust. Four of the sites on the Wombat Plateau provide a composite sedimentary record during Triassic (248-213 Ma) rifting and the Cre- taceous to Cenozoic (144 Ma to the present). Two sites on the western central Exmouth Plateau provide a Cretaceous to Cenozoic record of passive margin evolution. The time of margin breakup is constrained by a major erosion surface at the end of the Neocomian 131-119 Myr). A period of oxygen depletion, marked by a black shale, occurs at the Cenomanian/Turonian boundary. Preliminary analysis suggests other important sequence boundaries on the Wombat Plateau, and generally good correlation with recognized patterns of global changes. (hbf)

89:3911 Peltzer, Gilles and Paul Tapponnier, 1988. Formation

and evolution of strike-slip faults, rifts, and basins during the India-Asia collision: an experimental approach. J. geophys. Res., 93(B12):15,085- 15,117.

Processes which governed the formation of large Tertiary strike-slip faults during the penetration of India into eastern Asia are investigated using plane strain indentation experiments on layered plasticine models. Results show that fault or shear zones form after only 7-10% bulk strain, and subsequent deformation is controlled by the geometry of fault patterns. The ubiquity of strain softening in experimental deformation and the widespread occurrence of shear zones in nature suggest that long-term deformation of continental lithosphere may be primarily influenced by the geometry of large faults which develop rapidly under increasing strain. The experiments simulate the evolution of the western ends of the strike-slip faults which appear analogous to trench-fault-fault junctions and suggest mechanisms for formation of extensional basins. Lab. de Tecton., Mecan. de la Lithosphere, Inst. de Phys. du Globe, 4 Place Jussieu, 75252 Paris Cedex 05, France.

89:3912 Ruff, L.J. and Hiroo Kanamori (eds.), 1989. Special

issue. Subduction zones, Part II. Pure appL Geophys., 129(1-2):282pp; 8 papers.

This is the second of two volumes describing the diverse aspects of subduction. Part I dealt with global-scale reviews and accretionary prism processes; Part II covers large-scale tectonics, subduction initiation, and earthquake occurrences. Among the topics included are passive margin vulnerability to


subduction; the trench-trench-trench triple junction of central Honshu; subduction of bathymetric highs; large quakes in the Macquarie Ridge complex; predicting ground motions for a hypothetical event in the Cascades; backarc activity at the Hikurangi convergent margin in New Zealand; unusual seismic coupling in the Bonin Arc; and the role of trench sediments in the subduction zone. (hbf)

89:3913 Seno, Tetsuzo and Takashi Takano, 1989. Seis-

motectonics at the trench-trench-trench triple junction off central Honshu. Pure appl. Geophys., 129(1-2):27-40.

Focal mechanisms and focal depths were determined using Worldwide Standardized Seismograph Net- work records to study the interactions and deformation of plates at the complex triple junction between the Pacific, North America, and Philippine Sea plates. South of the junction, deformation takes place along nearly vertical normal faults perpendicular to the Bonin Trench, perhaps representing an accommodation to the change in dip angle between northeast Japan and the Izu-Bonin arcs; north of the junction, movement extends farther landward and occurs along nearly vertical normal faults paralleling the Japan Trench, perhaps reflecting the loading of the Philippine Sea Plate. Still further north earthquakes represent the motion between only the Pacific and North America plates without the intervention of the Philippine Sea slab. Intl. Inst. of Seismol. and Earthquake Engng, Bldg. Res. Inst., Tsukuba, Ibaraki-ken 305, Japan. (hbf)

89:3914 Stock, Joann and Peter Molnar, 1988. Uncertainties

and implications of the Late Cretaceous and Tertiary position of North America relative to the Farallon, Kula, and Pacific plates. Tectonics, 7(6): 1339-1384.

Updated global plate reconstructions and calculated uncertainties of the Pacific, Kula, and Faral- Ion/Vancouver plates relative to North America are presented for selected times since 68 Ma. Major differences between these results and those of others are due to the use of more detailed Africa-North America reconstructions, separate Vancouver and Farallon plate reconstructions, and the assumption of a rigid Antarctica Plate during Cenozoic time. Uncertainties of the positions of the Pacific and North America plates since 26 Ma range up to _+ 100 km in position or from 1 to 3 m.y. in time. Pacific-North America displacement in the past 20 Ma is considerably less than that calculated by fixed hotspot reconstructions. Faral lon-North America convergence velocity decreased greatly between 56

and 50 Ma; a change in direction occurring some- time between 50 and 42 Ma may not correlate with the time of the Hawaiian-Emperor bend (43 Ma). Dept. of Earth and Planetary Sci., Harvard Univ., Cambridge, MA 02138, USA.

D280. Volcanism, magmatism 89:3915

Epp, David and N.C. Smoot, 1989. Distribution of scamounts in the North Atlantic. Nature, Lond., 337(6204):254-257.

An extensive collection of multi-narrow-beam bathymetric data is used to locate over 800 seamounts in the North Atlantic. Ridge crest-generated seamounts are formed only between Iceland and the Hayes fracture zone, where there are contributions of plume material to the mid-ocean ridge plumbing system. It appears that in the slow-spreading North Atlantic an injection of plume material into the ridge plumbing system is necessary for the formation of seamounts at the ridge crest. NSF, 1800 G St. NW, Washington, DC 20550, USA.

89:3916 Fornari, D.J. et al., 1988. Morphology and structure

of Loihi Seamount based on Seaheam sonar mapping. J. geophys. Res., 93(B 12): 15,227-15,238.

The new maps and perspective images from Sea- beam data define the major structural and physi- ographic features of the volcano. Constructional volcanism has been localized along the southern and northern rift zones and has been active there since early in the seamount's history. The asymmetry between eastern and western slopes is attributed to mass wasting on the west flank. The prominent kink in the present south rift zone may represent a fundamental readjustment of along-rift magma conduits caused by gravitational slumping. Lava cones and volcanic ridges form a continuous chain o f volcanic constructs around the periphery of the summit platform. The morphology and structural relationships of pit craters on the summit suggest that the southeastern pit is the youngest. This model predicts a N-S age progression for summit volcanism on Loihi. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA.

89:3917 Lewis, T.J. et al., 1988. Subducti6n of the Juan de

Fuca Plate: thermal consequences. J. geophys. Res., 93(B12): 15,207-15,225.

Terrestrial heat flux was measured in fjords, bore- holes, and offshore wells at sites across the conver-


gent margin of southwestern British Columbia. The heat flux above the subducting Juan de Fuca Plate steadily decreases landward from over 50 mW m -2 on the shelf to 25 mW m -: seaward of the Garibaldi Volcanic Belt. An abrupt increase to 80 mW m -2 over a distance of 20 km is centered 30 km seaward of the volcanic zone, and very large variations occur locally within the Pleistocene volcanic area. Meas- ured heat generation of crustal samples along the entire profile is low, 0.6-0.8 #W m -3. It is postulated that dehydration of subducting oceanic crust at and above 450°C absorbs heat and produces water which flows updip into the overlying subduction complex, redistributing heat seaward. A relatively cool crustal wedge lies above the deeper subducting oceanic crust; the abrupt increase in surficial heat flux at its thick landward side must be caused by a shallow heat source produced by ascending magma. Geol. Survey of Canada, Pacific Geosci. Centre, P.O. Box 6000, Sidney, BC V81 4B2, Canada.

89:3918 Lightfoot, Peter and Chris Hawkesworth, 1988.

Origin of Deccan Trap lavas: evidence from combined trace element and Sr-, Nd- and Pb- isotope studies. Earth planet. Sci. Letts, 91(1- 2):89-104.

Geochemical and isotope results are presented from a new study of the most southern basalts in the Deccan Trap, India. Three chemical formations are recognized, two of which can be correlated with the established stratigraphy in Mahabaleshwar and imply a regional southerly dip of 0.06 over a distance of 250 km. New major, trace element and Sr, Nd, and Pb isotope data are presented which identify several endmembers responsible for the isotope variations and shed new light on the nature of the subcontinental mantle and the interaction between asthenospheric and lithospheric material. Geosci. Lab., Ontario Geol. Survey, 77 Grenville St., l lth FI., Toronto, ON, Canada.

89:3919 Nelson, C.H., P.R. Carlson and C.R. Bacon, 1988.

The Mount Mazama climactic eruption (~6900 yrBP) and resulting convulsive sedimentation on the Crater Lake caldera floor, continent, and ocean basin. Spec. Pap. geol. Soc. Am., 229:37-58.

The eruption of Mount Mazama, perhaps 'the most significant convulsive sedimentary event in North America during Holocene time,' produced deposits of pyroclastic ash that covered > 1,000,000 km 2 of the continent, creating a Mid-Holocene stratigraphic marker across North America and its western continental margin. The eruption included an initial single-vent phase producing the pumice deposit, a

ring-vent phase resulting in flows extending at least 14 km from the vent and 60 km down valley, and the phase marked by development of phreatic explosion craters on the caldera floor. The acoustic stratigraphy of the area is described along with the widespread effects of the eruption and the damage potential likely to be associated with such an event today. USGS, 345 Middlefield Rd., Menlo Park, CA 94025, USA. (hbf)

89:3920 Rhodes, J.M. et al., 1989. Geochemical evidence for

invasion of Kilauea's plumbing system by Mauna Loa magma. Nature, Lond., 337(6204):257-260.

Although on rare occasions they have erupted concurrently, the brief historical record appears to show that when Kilauea is most active, Mauna Loa is in repose and vice versa, suggesting that they may be competing for the same magma supply. Petro- logical, geochemical and isotope data, however, require a diametrically opposite conclusion. Distinct differences in major-element, trace-element and isotope compositions of lavas are regarded as compelling evidence that the two volcanoes have separate magmatic plumbing systems. Here we present preliminary geochemical data which show that in the past 2,000 yr Kilauea has erupted a spectrum of lava compositions resembling historical Kilauea lavas at one end and Mauna Loa lavas at the other. We discuss the cause of this diversity, and speculate that magma from Mauna Loa may have invaded Kilauea's 'high-lever magmatic plumbing system. Dept. of Geol./Geogr., Univ. of Mass., Amherst, MA 01003, USA.

89:3921 Sarda, Philippe, Thomas Staudacher and C.J.

Allrgre, 1988. Neon isotopes in submarine basalts. Earth planet. Sci. Letts, 91(1-2):73-88.

Very large neon isotopic anomalies have been accurately measured in mid-ocean ridge basalt glassy samples from diverse locations worldwide. Values for 2°Ne/22Ne range up to ~ 13 and 2~Ne/22Ne values up to ~0.07. Loihi Seamount data show an atmospheric neon isotopic composition, which is consistent with previous He-Ar-Xe data and their interpretation as representative of a deep undegassed mantle source. Recent mixing within the mantle best explains the neon isotopic features, as well as the He -Ne-Ar -Xe relationships. It is suggested that MORB 2WNe/22Ne anomalies are due to nuclear reactions within the mantle. Lab. de Geochim. et Cosmochim., Inst. de Phys. du Globe, 4 place Jussieu, 75252 Paris Cedex 05, France.


89:3922 Scrutton, R.A. and P.A.D. Bentley, 1988. Major

Cretaceous volcanic province in southern Rockali Trough. Earth planet. Sci. Letts, 91(1-2): 198-204.

A group of three large curvilinear ridges, each about 2 km high and 20 km wide at its base, has been mapped in the acoustic basement of southern Rockall Trough. Evidence points to a volcanic- sedimentary composition for the ridges. Seismic continuity with the acoustic basement of the rest of Rockall Trough suggests that the trough basement is of similar composition. A ridge age of Lower Cretaceous is indicated. Volumetrically, the ridges are on the scale of hotspot features such as the Wyville-Thomson Ridge. Grant Inst. of Geol., W. Mains Rd., Edinburgh EH9 3JW, UK.

89:3923 Sharkov, Ye.V. and A.A. Tsvetkov, 1988. Origin of

magmas in active continent-ocean transition zones. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 294(1-6):107-109.

Continent-ocean transition zones are known to include virtually all the igneous rock types found in the present Earth. These rocks are the products of two different types of magma generation--those produced by melting mantle, analogous to the intraplate magmatism found on the Hawaiian Is- lands, and those due to subduction, which involves melting of hydrated crustal material that has de- scended to the melting zone and its overlying mantle wedge. The probable sequence of events during magma generation and the problem posed by the occurrence of subalkalic K-Na volcanism on island arcs proper are discussed. Inst. of Economic Geol., Petrol., Mineral. and Geochem., Acad. of Sci., Moscow, USSR. (hbf)

89:3924 Tilling, R.I. (guest editor), 1988. Special section.

How volcanos work, Part 3. J. geophys. Res., 93(B12):14,757-14,880; 10 papers.

Collectively the three parts of 'How Volcanoes Work,' are planned to provide a sampling of the nearly 300 papers presented at the 1987 international symposium by that name, commemorating the 75th anniversary of the founding of the Hawaiian Vol- cano Observatory and attesting to the multidisciplinary nature of modern studies on volcanology. The papers in this section supply information on Mount Etna, Mount St. Helens, the Vesuvius eruptions of 79 A.D., the Kurile Island Arc, Woods Mountains Volcanic Center in southeastern Cali- fornia, and Momotombo Volcano in Nicaragua, as well as on several of the Hawaiian volcanoes.

Discussions of the growth of aa lava fields, loading by shallow intrnsives, magma storage and conduit systems, erosional furrows, petrochemical variations of island arc andesite, genesis of peralkaline rhyolite ash flow tufts, relationship between sulfur dioxide emission and Earth tides, and the application of oxygen fugacity to volcanologicai monitoring are included. (hbf)

89:3925 Yu, Liansheng, Qinchen Cao and Xu Yu, 1988.

Study on tholeiitic basalt of Juan de Fnca Ridge. J. Shandong Coll. Oceanol., 18(2):56-68. (In Chinese, English abstract.)

Geochemical analysis of a sample of tholeiitic basalt taken from the rift valley at 2425 m depth reveals slightly higher percentages of Ca and Mg and slightly lower percentages of Si and K than the average tholeiite, suggesting that the rock was an early-stage product of the differentiation of mantle magma. Major minerals are labradorite and augite. The presence of higher percentages of Cu, Co, and Ni within the glassy rind than within the crystalline interior of the sample implies an interaction with seawater. The age of the sample, based on isotopic dating, is 340,000 yrBP. Shandong Coll. of Oceanol., Qingdao, People's Republic of China. (hbf)

89:3926 Zharinov, S.E., 1988. Petrochemical variations of

island arc andesites (Kurile Island Arc). J. geophys. Res., 93(B12): 14,828-14,834.

In the case of the Kurile Arc, two main factors, based on multivariate statistical analysis, govern the petrochemical variety of andesites. The first ('mantle') factor is the depth to the Benioff seismic zone, and the second ('crustal') factor is the position of the peripheral magma chamber. Trends in the variations of the initial chemical components depending on changes in the controlling factors have been determined. The chemical composition of volcanics depends on the type and structure of the crust. Inst. of Volcanol., Petropavlovsk-Kamchatsky, USSR.

D290. Crust, mantle, core

89:3927 Agrinier, Pierre, Marc Javoy and Jacques Girardeau,

1988. Hydrothermal activity in a peculiar oceanic ridge: oxygen and hydrogen isotope evidence in the Xigaze ophiolite (Tibet, China). Chem. Geol~ 71(4):313-335.

The Xigaze ophiolite locally displays a 7-km-thick continuous sequence which probably represents an


oceanic crust formed at a slow spreading ridge. It consists from top to bottom of pillow-lavas, rare trondjhemites, dolerite sills and dikes, isotropic and rare layered gabbros, and ultramafic rocks, either fresh or serpentinized. Oxygen and hydrogen stable- isotope results on samples from the ophiolite indicate that there is very little ~80-depleted rocks, and that they cannot balance the amount of ~sO-enriched rocks. Consequently the results of hydrothermal interaction between the Xigaze ophiolite sequence and seawater is an ~so depletion of the seawater. However, the contribution of the Xigaze- type 'ridges' to the buffering of 8zsO in Cretaceous seawater was probably small. Lab. de Geochim. des Isotopes Stables, Inst. de Phys. du Globe, Univ. Paris VI, F-75230 Paris Cedex 05, France.

89:3928 Anderson, D.L., 1989. Composition of the Earth.

Science, 243(4889):367-370.

New estimates of solar composition, compared to earlier measurements, are enriched in Fe and Ca relative to Mg, A1, and Si. The Fe/Si and Ca/Al atomic ratios are 30--40% higher than chondritic values. These changes necessitate a revision in the cosmic abundances and in the composition of the nebula from which the planets accreted. These new values imply that the mantle could contain about 15% by weight FeO and more CaMgSi:O 6 than has been supposed. Geophysical data are consistent with a dense, FeO-rich lower mantle and a CaMgSi206 (diopside)-rich transition region. FeO contents of 13-18% by weight appear to be typical of the mantles of inner solar system bodies. The oldest komatiites have a similar chemistry to the derived mantle. These results favor a chemically zoned mantle. ©1989 by AAAS. Seismol. Lab., Calif. Inst. of Tech., Pasadena, CA 91125, USA.

89:3929 ECORS-CROP Deep Seismic Sounding Group, A.

Hirn, S. Nadir and F. Thouvenot, 1989. A new picture of the Moho under the western Alps. Nature, Lond., 337(6204):249-251.

A tight sampling of this deep reflector across the western Alps shows abrupt changes in its depth and dip. The root zone of the chain (the zone of maximum crustal thickness) is well defined, with a 55-kin-deep crust-mantle boundary. The Moho under the western Po plain is also clearly seen, and a shallow reflective structure is mapped under the Brianctonnais zone in the 25-30 km depth range. This structure, if interpreted as lower-crustal or upper- mantle material, would support the hypothesis of a flaking of the lithosphere under the western Alps. Thouvenot: Lab. de Geophys. Interne et Tec-

tonophys., Observ. de Grenoble, IRIGM, 38041 Grenoble, France.

89:3930 Goleby, B.R. et al., 1989. Geophysical evidence for

'thick-skinned' crustal deformation in central Australia. Nature, Lond., 337(6205):325-330.

Until now, there has been no clear evidence from deep seismic reflection profiles of crustal faults that displace the Moho. New data from central Australia show such a structure in a region characterized by large thrust structures, large gravity anomalies and abrupt changes in teleseismic travel times. Here the principal thrust, the Redbank Deformed Zone, cuts through the crust, and the Moho is significantly displaced across it. The evidence leads to a model of thick-skinned crustal deformation which occurred in an intra-cratonic environment in the Late Devonian. Bur. of Mineral Resour., Geol. and Geophys., G.P.O. Box 378, Canberra ACT 2601, Australia.

89:3931 Hay, W.W., J.L. Sloan II and C.N. Wold, 1988.

Mass/age distribution and composition of sediments on the ocean floor and the global rate of sediment subduction. J. geophys. Res., 93(B12): 14,933-14,940.

The total mass of sediments on the ocean floor is estimated to be 262 x 102] g. Mass/age distribution is a function of area/age distribution of ocean crust, supply of sediment to the deep sea, and submarine erosion and redeposition. About 140 x 102~ g of seafloor sediment is pelagic and 122 x 102~ g is detritus, mostly terrigenous, but with a small proportion of volcanics. Virtually all pelagic sediment and some terrigenous sediment is subducted at a rate estimated at 1 x 102j g per m.y. The composition of ocean floor sediment differs significantly from that of the passive margin and continent so that loss of ocean floor sediment through subduction may drive the composition of global sediment toward enrichment in silica, alumina, and potash and depletion in calcium. Dept. of Geol., Univ. of Colorado, Boulder, CO 80309, USA.

89:3932 Heaton, T.H. and S.H. Hartzell, 1989. Estimation of

strong ground motions from hypothetical earthquakes on the Cascadia Subduction Zone, Pacific Northwest. Pure appl. Geophys., 129( 1-2): 131-202. USGS, 525 S. Wilson Ave., Pasadena, CA 91106, USA.

89:3933 Helffrich, G.R., Seth Stein and B.J. Wood, 1989.

Subduction zone thermal structure and miner-


alogy and their relationship to seismic wave reflections and conversions at the slab/mantle interface. J. geophys. Res., 94(B1):753-763.

Using a petrologic model of mantle and slab mineralogy and a data base of elastic properties of mantle and slab phases, theoretical seismic velocities were calculated and compared with observed velocity contrast and boundary thickness constraints to investigate whether the observed sharp contrasts can result from thermal structure, compositional differences, phase changes, or other effects. The results indicate that the contrasts are substantially lower than those obtained from seismological studies and that temperature and bulk compositional differences between mantle and slab are inadequate to cause the observed velocity contrast. It is proposed that phase transformations in mantle and slab mineralogies are important factors in these sharp contrasts. Other contributing effects may include preferential mineral orientation and, at shallower depths, the presence of partial melt or hydrous fluid from dehydration reactions. Dept. of Geol. Sci., Northwestern Univ., Evanston, IL 60208, USA.

89:3934 Hinze, W.J., 1988. Scientific drilling into the Mid-

continent Rift System [of North Americal. Eos, 69(51): 1649, 1656-1657.

89:3935 Hodder, A.P.W., 1988. A mantle heterogeneity in the

southwest Pacific. Tectonophysics, 156(1-2): 145- 165.

The occurrence in time and space of Tertiary intraplate volcanoes in the eastern Australia-New Zealand-Campbell Plateau region of the southwest Pacific is more consistent with derivation from a large-scale mantle anomaly than from discrete plumes. The eastern basalt volcanics show a pronounced geochemical similarity; those near the Indo-Australia-Pacific plate boundary show some evidence of interaction with subduction-derived basalts. Dept. of Earth Sci., Univ. of Waikato, Hamilton, New Zealand.

89:3936 Hsu, K.J., 1988. [Lecturel: The geology of ocean

floor. Mar. Geol. Quat. Geol., 8(2):1-13. (In Chinese, English abstract.) Swiss Fed. Inst. of Tech., Geol. Inst., CH-8092 Zurich, Switzerland.

89:3937 Izzeldin, A.Y., 1989. Transverse structures in the

central part of the Red Sea and implications on early stages of oceanic aco'etion. Geophys. J., 96(1):117-129.

Transverse structures in the central Red Sea are mapped according to bathymetric, seismic, gravity and magnetic data. Five classes of structures are detected. Three of these are fractures, intertrough zones and transform faults. The remaining two are classified as transform zones and pseudo-transform faults. Most structures can be related to ancient lineaments on land. Intertrough and transform zones are manifestations of unorganized seafloor spreading, and their crustal structure is of an oceanic nature that might be similar to quiet magnetic zones. Geophys. Dept., Min. of Energy and Mining, P.O. Box 410 Khartoum, Sudan.

89:3938 KAIYO 87 (shipboard party), 1988. Rift system in

the North Fiji Basin: results of Japan-France cooperative research on board KAIYO 87. Mer, Tokyo, 26(1):36-46. (In Japanese, English abstract.)

89:3939 Kalinin, A.V., B.L. Pivovarov and I.D. Tsvankin,

1987. Dynamic characteristics of bottom Stoneley waves and possibilities for their use in seismo- acoustics. Oceanology (a translation of Okeano- logiia), 27(6):710-714.

The results of numerical modeling of the total wave field excited by a point source near the boundary between liquid and solid media are presented. The dynamics of Stoneley waves formed at the boundary are largely governed by the velocity of transverse waves in the elastic medium and their absorption coefficient. A formula relating the amplitude of Stoneley waves to the absorption coefficient for transverse waves with a nonlinear frequency dependence of the absorption coefficient is derived. Shmidt Inst. of Earth Phys., Acad. of Sci., Moscow, USSR.

89:3940 Lago, B., 1988. Mechanical behavior of the oceanic

lithosphere at a corner area defined by an axial valley and a large offset transform fault: case of the Oceanographer Transform Fault. J. geophys. Rex. 93(B12): 15,135-15,151.

Elastic behavior of lithospheric plates can account for the return to the isostatic equilibrium level observed where a mid-ocean ridge axial valley and a large offset transform fault intersect. Good agreement of depth profiles of the oceanic platform can be obtained between models and data for the two corner areas associated with the Oceanographer Transform Fault. A major result of the study concerns the evaluation of the static contribution, due to anomalous crust, in the deepening of the


crustal valley in the vicinity of the fault to a value of 50-70%; the residual 30-50% is attributed to an increase of the dynamical effect of asthenospheric upwelling, feeding the lithospheric plates. Centre Natl. d'Etudes Spatiales, Groupe de rech. de Geod. Spat., 18 Ave. Edouard Belin, 31055 Toulouse Cedex, France.

89:3941 Lay, Thorne, 1989. Structure of the core-mantle

transition zone: a chemical and thermal boundary layer. Eos, 70(4):49, 54-55, 58, 59.

The transition zone (2900 km below the surface) profoundly influences the style of mantle convection, plume formation, secular variation and possibly reversals of the magnetic field, core-mantle ex- changes of angular momentum, long-wavelength gravitational variations, and chemical evolution of the Earth. Recent contributions to our understanding of this dynamic region are synthesized here, and a model with a combined thermal and chemical boundary layer at the core-mantle boundary is proposed. Dept. of Geol. Sci., Univ. of Michigan, Ann Arbor, MI, USA.

89:3942 Linde, A.T. et al., 1988. Episodic aseismic strain

signals; precursors to the Japan Sea earthquake of 1983. Tohoku geophys. J., (5)31(2):29-41. Dept. of Terrestrial Magnet., Carnegie Inst. of Wash- ington, 5241 Broad Branch Rd. NW, Washing- ton, DC 20015, USA.

89:3943 La, Bingquan and Xianjin Shi, 1988. Wave char-

acteristics of crustal tectonics in continental margins. Scientia sin., (B)31(10):1245-1257. Dept. of Mar. Geol., Tongji Univ., Shanghai, People's Republic of China.

89:3944 Lyon-caen, H. et al., 1988. The 1986 Kalamata (south

Peloponnesus) earthquake: detailed study of a normal fault, evidences for east-west extension in the Hellenic Arc. J. geophys. Res., 93(B12): 14,967-15,000.

Tectonic and seismological data collected in the field following the earthquake show that the event occurred on the Kalamata normal fault, which is part of a NNW-SSE en echelon system cutting the Hellenic nappes. The main shock focal mechanism, obtained from long-period waveform modeling, is in good agreement with observations. Centroid depth is constrained to 5-+3 km and seismic moment to 7.0-+2.5 x 10 j7 N m. Over 700 aftershocks were also recorded and analyzed. The focal mechanism of the

event and that of the April 27, 1965 earthquake northwest of Crete, as well as the regional active normal fault pattern imply that E-W extension oblique to the Hellenic Arc is presently the dominant tectonic regime. The E-W extension implies a recent change in tectonic regime and boundary conditions at the subduction zone, probably in response to the incoming margin of Africa. Lab. de Sismol., Inst. de Phys. du Globe de Paris, 4 place Jussieu, 75252 Paris Cedex 05, France.

89:3945 Maaloe, Sven and Ole Tjugen, 1988. Implication for

mantle flow from the Hawaiian-Emperor chain. Earth planet. Sci. Letts, 91(1-2): 170-178.

Assuming that Rayleigh-Benard flow occurs within the upper mantle, ascending plumes must undergo horizontal displacement during ascent that can be traced at the surface. The Hawaiian-Emperor bend cannot be formed if the convection rate is of the same order of magnitude as the ascent rate of the plumes. The plume patterns obtained by push-pull or lithospheric sliding are similar to that of the Hawaiian-Emperor chain, thus these results support the sliding model. Dept. of Geol., Allegaten 41, 5007 Bergen, Norway.

89:3946 Matsu'ura, Mitsuhiro and Toshinori Sato, 1989. A

dislocation model for the earthquake cycle at convergent plate boundaries. Geophys. J., 96(1): 23-32.

Dislocation theory is used to develop a model for the earthquake cycle at convergent plate boundaries. The surface deformation involved is determined by 'superposition of viscoelastic responses to steady slip on the interface at depths shallower than the lithosphere/asthenosphere boundary; steady back- slip on the seismic zone; and the periodic sequence of seismic slips.' Cyclic patterns of vertical dis- placements are computed for two representative cases. It is suggested that the model may provide an explanation for the formation of marine terraces generated by earthquakes. Geophys. Inst., Univ. of Tokyo, Japan. (hbf)

89:3947 Meyer, Klaus, Rune Olsson and SOren Scherman,

1988. Stress migration in the North Atlantic and intraplate seismicity in Scandinavia---a proposal. Tectonophysics, 156(1-2): 175-178.

Remnant stresses in the lithosphere due to stress accumulation over geological times may have minor impact on the seismicity in Fennoscandia. Alter- natively, the driving forces of plate motions may be


responsible for intraplate seismicity in Scandinavia. It is suggested that stresses at the nearest plate margin (North Atlantic Ridge) are connected to intraplate stresses (Scandinavia, North America) by stress migration. Thus, it may be assumed that seismic energy release along the plate margin is also correlated with intraplate seismicity taking place at intraplate boundaries, regional fracture zones or rheological zones of weakness in general. Seismol. Dept., Box 12019, S-750 12 Uppsala, Sweden.

89:3948 Monnereau, Marc and Army Cazenave, 1988. Vari-

ation of the apparent compensation depth of hotspot swells with age of plate. Earth planet. Sci. Letts, 91(1-2): 179-197.

Most oceanic hotspot swells are associated with anomalously shallow seafloor and broad geoid anomalies, whose linear relationship can be used to infer an apparent depth of isostatic compensation of the swell. We have analysed geoid and depth anomalies over 23 oceanic hotspot swells and deduced the apparent depth of compensations of these features. The data indicate a linear increase of the compensation depth with the square root of seafloor age; this trend is comparable to that predicted by conductive cooling models for the deepening of the isotherms inside the oceanic lithosphere. Centre Natl. d'Etudes Spatiales, Groupe de Rech. de Geod. Spatiale, 18, Ave. Edouard Belin, 31055 Toulouse Cedex, France.

89:3949 Moriyama, Tetsuji, Fumiko Tajima and Tetsuzo

Seno, 1989. An unusual zone of seismic coupling in the Bonin Arc: the 1972 Hachijo-Oki earthquakes and related seismicity. Pure appl. Geophys., 1290-2):233-261.

An analysis of the rupture process for the M~ = 7.3 and 7.4 Hachijo-Oki earthquakes in February and December, 1972, demonstrates that rupture prop- agated upward in both events and that the later event was 10 km deeper than the earlier one, probably representing overlap within the rupture zone. Data on subsequent smaller events show that they were non-thrusting events occurring deeper within the descending slab, perhaps triggered by the rupture which loaded down-dip compressional stress near the down-dip end of the rupture zone. Dept. of Earth Sci., Tsukuba Univ., Sakuramura, Niihari, Ibaraki 305, Japan. (hbf)

89:3950 Neprochnov, Y.P. et al., 1988. The structure and

tectonics of the intraplate deformation area in the Indian Ocean. Tectonophysics, 156(!-2):89-106.

Intense tectonic deformation of sediments and basement, unusual for the interior of oceanic lithosphere plates, can be seen on seismic reflection profiles from the north central Indian Basin. The intraplate deformation area has a complicated tectonic framework formed by a mosaic of tilted or deformed crustal fault blocks alternating with less deformed seafloor. There is a high-level intraplate seismicity in the region. It is suggested that the continued collision of India and Asia led to an increase in compressional stress in the northernmost part of the plate while its southern part continuously subducted beneath the Sunda Trench. In the complicated transition zone between them, NE-SW shearing stress resulted in the folding and faulting of sediments and basement until the Late Miocene. The mosaic fault-fold intraplate deformation may have been a part of this interaction. P.P. Shirshov Inst. of Oceanol., Moscow 117218, USSR.

89:3951 Obara, Kazushige and Haruo Sato, 1988. Existence

of an S wave reflector near the upper plane of the double seismic zone beneath the southern Kanto District, Japan. J. geophys. Res., 93(B12): 15,037- 15,045.

The amplitude of coda from local shallow earthquakes in the southern Kanto district does not decay smoothly with time. A clear phase in the S coda at 15~15 s from the S wave arrival seems to be an S wave reflected from a discontinuity inclined westward at upper mantle depths. Application of an inversion method to travel times located the S wave reflector near the upper plane of the double seismic zone associated with the subducting Pacific Plate. The S wave impedance contrast at the interface seems to be very large and may suggest the existence of a zone containing many liquid bodies. Natl. Res. Ctr. for Dis. Prev., Sci. and Tech. Agency, Tennodai 3-1, Tsukuba-shi, Ibaraki-ken 305, Japan.

89:3952 Ogawa, Masaki, 1988. Numerical experiments on

coupled magmatism--mantle convection system: implications for mantle evolution and Arcbean continental crusts. J. geophys. Res., 93(BI2): 15,119-15,134.

The chemical and thermal evolution of mantle is investigated by numerical experiments on the coupled mantle magmatism-mantle convection system. Mantle evolution depends strongly on two quan- t i t i e s - the internal heating rate and the density of undifferentiated mantle mater ia l - -and specific ranges of these values define three basic types of magmatism. Values for the density factor are also shown to control whether mantle magmatism occurs


continuously or episodically. Estimated values appropriate for the Earth's mantle and known features of the Archean continental crust, indicate that Archean mantle evolution occurred beneath the continental crusts, and many features of Archean continental crusts fit within the framework of this type of mantle evolution. Dept. of Earth Sci., Ehime Univ., Bunkyo-chu, Ehime, 790, Japan.

89:3953 Olson, Peter et al., 1988. Plume formation and

lithosphere erosion: a comparison of laboratory and numerical experiments. J. geophys. Res., 93(B 12): 15,065-15,084.

Plumes develop, ascend, and partially intrude overlying cold layers when a deep layer of viscous sucrose solution is heated from below and cooled from above. A set of two-dimensional finite element calculations using the experimental data successfully reproduced the qualitative features seen in the experiment with a quantitative discrepancy of 30% or less. Numerical simulations of mantle plume- lithosphere interaction with subsolidus creep theology show that thermal plumes do not effectively intrude and erode the lithosphere if upper mantle viscosity is a function of temperature only, unless activation energy is anomalously low. However, plumes can significantly erode the lithosphere on time scales of 10-20 m.y. if a low-viscosity pressure- dependent asthenospheric channel is present. Dept. of Earth and Planetary Sci., Johns Hopkins Univ., Baltimore, MD 21218, USA.

89:3954 Ozima, M. et al., 1989. Origin of the anomalous

4°Ar-39Ar age of Zaire cubic diamonds: excess 4°At in pristine mantle fluids. Nature, Lond., 337(6204):226-229. Geophys. Inst., Univ. of Tokyo, Tokyo 113, Japan.

89:3955 Pushcharoskiy, Yu.M. et al., 1988. Crustal structure

and types of Cuba. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 194(1- 6):47-50.

The island of Cuba includes regions of continental, transitional, and suboceanic crust. North central Cuba has typical continental crust, 22-30 km thick, consisting of granitic-metamorphic and mafic layers of roughly equal thickness and 5-7 km of sedimentary cover. Paleotectonically, the area derives from North America. The crust of western Cuba, 24-30 km thick, is also continental, but derives from both North and South America. South of the main geosuture is a 28-32-kin-thick transitional crust distinguished by a mafic layer up to 20-km thick. Its

northern portion includes a wide belt of Cretaceous island-arc series, whereas its southern portion abounds with metamorphic rocks. To the east is suboceanic crust which was generated in Maastrichtian-Paleocene time, only 14-18-km thick, lacking seismic boundaries and cut by large strike- slip faults. Geol. Inst., Acad. of Sci., Moscow, USSR. (hbf)

89:3956 Ruff, L.J., 1989. Do trench sediments affect great

earthquake occurrence in subduction zones? Pure appL Geophys., 129(1-2):263-282.

Research has shown that variation in maximum earthquake size can be correlated with variations in age of subducting lithosphere and convergence rate. A global survey of great earthquakes and subduction zones shows that most great earthquakes occur in zones with excess trench sediments and that roughly half the zones with excess sediments are also sites of major earthquakes, leading to the hypothesis that excess trench sediments constitute a third variable for the size of major earthquakes. This apparent correlation may reflect the fact that excess sediment is generally associated with a subducting, coherent sedimentary layer which under high pressure and temperature acts as a homogeneous, strong contact zone between plates. Dept. of Geol. Sci., Univ. of Michigan, Ann Arbor, MI 48109, USA. (hbf)

89:3957 Ruff, L.J. et al., 1989. Large earthquakes in the

Macquarie Ridge complex: transitional tectonics and subduction initiation. Pure appl. Geophys., 129(1-2):71-129.

Subduction initiation is presently taking place in the transitional tectonic environment of the Macquarie Ridge complex on the Pacific-Australia plate boundary between New Zealand and the Pacific- Australia-Antarctica triple junction, where 15 earthquakes (M:>7) have occurred in this century. A study of seismicity in the Puysegur Trench demonstrates that oblique convergence is accommodated by large strike-slip earthquakes on vertical fault planes and smaller thrust earthquakes on low angle, discontinuous fault planes, supporting a subduction initiation model based on the idea of crack propagation. However, a different mechanism for subduction is required for the aseismic southernmost Hjort Trench region, where there is newly created lithosphere. Dept. of Geol. Sci., Univ. of Michigan, Ann Arbor, MI 48109, USA. (hbf)

89:3958 Rydelek, P.A. and I.S. Sacks, 1989. Testing the

completeness of earthquake catalogues and the


hypothesis of serf-similarity. Nature, Lond., 337(6204):251-253.

Self-similarity of the earthquake process is consistent with the observed linear b-value relation log (N) = a - bM, where N is the number of earthquakes with magnitude M. Deviations from linearity are believed to be due to statistical fluctuations because of the scarcity of events at large M, or from incompleteness because of a detection threshold at small M (events go undetected as the seismic signal approaches the noise background). Thus more of the smallest events should be logged at night than during the day, because the cultural noise sources and winds are diminished at night, resulting in pre- sumably quieter seismograms. Based on this, we test three catalogues and show that the completeness magnitude can be different from the magnitude at which the b-value departs from linearity. In particular, catalogues that show significant deviations in linearity at small M but are otherwise complete, are at odds with the hypothesis of earthquake self- similarity. Dept. of Terr. Mag., Carnegie Inst., 5241 Broad Branch Rd. NW, Washington, DC 20015, USA.

89:3959 Sieh, Kerry, Minze Stuiver and David Brillinger,

1989. A more precise chronology of earthquakes produced by the San Andreas Fault in southern California. J. geophys. Res., 94(B1):603-623.

Improved methods of radiocarbon analysis have made it possible to date more precisely earthquake ruptures of the San Andreas Fault that are recorded in sediments at Pallett Creek. New error limits are ~ 2 3 yr for all but two of the dated events. T h e estimate for the average interval between the latest l0 episodes of faultings is now ~132 yr, but variability about the mean interval is much greater than suspected previously. Five of the nine intervals are shorter than a century; three are two to three centuries long. The last l0 earthquakes occur in four clusters, each consisting of two or three events. Earthquakes within the clusters are separated by several decades; clusters are separated by dormant periods of two-three centuries. If this pattern continues, the current period of dormancy will probably be greater than two centuries. Div. of Geol. and Plan. Sci., Calif. Inst. of Tech., Pasadena, CA 91125, USA.

89:3960 Tanada, Toshikazu et al., 1988. Hypocenter distri-

Imtion of micro- and uitramicroearthquakes in the vicinity of the Fuji River around Suruga Bay, central Japan (1981-86). J. Fac. mar. Sci.

Technol., Tokai Univ., 26:17-26. (In Japanese, English abstract.)

89:3961 Tanada, Toshikazu, Ryuji Kubota and Masami

Hayakawa, 1988. Source parameters of earthquake swarm off east coast of Izu Peninsula in 1980. J. Fac. mar. Sci. Technol., Tokai Univ., 26:1-15. (In Japanese, English abstract.)

89:3962 Utsu, Tokuji, 1988. Relation between seismic inten-

sity near the [earthquake] epicenter, focal depth and magnitude. Bull. Earthq. Res. Inst., Univ. Tokyo, 63(1):p.31. (In Japanese, English abstract.) Earthquake Res. Inst., Univ. of Tokyo, Japan.

89:3963 Yeganeh-Haeri, A., D.J. Weidner and E. Ito, 1989.

Elasticity of MgSiO 3 in the perovskite structure. Science, 243(4892):78%789.

The single-crystal elastic moduli of MgSiO 3 in the perovskite structure, the high-pressure polymorph of MgSiO 3 pyroxene, have been determined. The data indicate that a mantle with either pyrolite or pyroxene stoichiometry is compatible with seismic models appropriate to the lower mantle, provlded that the shear modulus of MgSiO 3 perovskite exhibits a strong negative temperature derivative. Such a temperature derivative falls outside the range expected for a well-behaved refractory ceramic and could result if the pressure-temperature regime of the earth's lower mantle is near that required for a ferroelastic phase transformation of the perovskite phase. ©1989 by AAAS. Dept. of Earth and Space Sci., SUNY, Stony Brook, NY 11794, USA.

D330. Oil and gas

89:3964 Bailliet, R.M., 1987. PC-based SCADA [supervisory

control and data acquisition] system spans the Gulf of Mexico. InTech, 34(9):59-64.

Shell's automated system to monitor safety conditions and production status of its Gulf of Mexico platforms is described. Sensors throughout a platform send data to a remote data processing unit that performs limited control functions and also reports status to a land-based computer via a microwave communications channel. The system costs about $50,000 per platform, but has enabled continuing production during hurricanes, reduced the labor force required, and reduced the required number of


routine helicopter flights for data acquisition pur- poses. Shell Offshore Inc., New Orleans, LA, USA. (fcs)

89:3965 Bazylinski, D.A., J.W. Farrington and H.W.

Jannasch, 1988. Hydrocarbons in surface sediments from a Guaymas Basin hydrothermal vent site. Org. Geochem., 12(6):547-558.

Petroleum-like materials found at the site are derived from pyrolysis of organic matter. Two characteristic surface sediment cores differing in temperature profiles and other parameters were sectioned and analyzed for hydrocarbons. The quantitative and qualitative composition of alkanes, steranes, dia- steranes, and triterpanes differed between these cores as well as within sections of the same core. These differences, apparent for scales of tens of centimeters, are related to interactive physical, chemical, and microbial processes as well as the influence of multiple sources for the petroleum. WHOI, Woods Hole, MA 02543, USA.

89:3966 Cooper, A.K., F.J. Davey and Karl Hinz, 1988.

Antarctica-l: Ross Sea-geology, hydrocarbon potential. Oil Gas J., 86(45):54-58.

The regional setting, framework, crustal structure, seismic stratigraphy, and tectonic history of the Ross Sea are covered in Part I of this report. Three major depocenters, underlain by Late Mesozoic to Early Cenozoic rift graben structures, which include sedimentary sequences, unconformably overlain by Middle Eocene to Early Oligocene and younger glacial marine rocks, have been identified. Renewed movements along the graben-bounding faults have taken place from the Eocene on. The hydrocarbon potential of the area remains uncertain because, although seismic data reveal the presence of potential structural traps, no rocks older than the glacial deposits have been recovered to date. Office of Mar. Geol., USGS, Menlo Park, CA, USA. (hbf)

89:3967 Einarsson, T.D. and James Spackman, 1988. Marine

systems: a quiet revolution. Oil Gas J , 86(44): 83-87.

In spite of the downturn in oil prices in 1986, marine geophysical exploration has been undergoing dra- matic technological improvements. Tunable arrays of sleeve type airguns; digital, relatively noise-free hydrophone streamer arrays with fiber optic links to the ship; global positioning and systems component positioning; and real-time integration of signals and positioning information are all described. In sum,

great improvements in resolution, accuracy and depth of penetration have all been realized. Mar- keting and Strategic Develop., Geophys. Serv. Inc., Dallas, TX, USA.

89:3968 Guo, Zhenxuan, 1988. Characteristics of geologic

structure and hydrocarbon potential of the East China Sea. Mar. Geol. Quat. Geol., 8(3):35-41. (In Chinese, English abstract.)

The East China Sea Basin is structurally complex and includes numerous traps for the accumulation of hydrocarbons. In the Early Cenozoic, faulting within a basin-and-range-type province restricted deposition. From the Oligocene to Late Miocene however, uplift in the west and subsidence in the east favored deposition along the East China Sea shelf basin. During the Pliocene hydrocarbons migrated westward, but in the Neogene hydrocarbons migrated toward the east and west. Both the Xihu and Qilum depressions are considered important sites for large hydrocarbon reservoirs. Inst. of Mar. Geol., Min. of Geol. and Mineral Resour., Qingdao, People's Republic of China. (hbf)

89:3969 He, Liansheng, 1988. Formation and evolution of

South China Sea and their relation to hydrocarbon potential. Mar. Geol. Quat. Geol., 8(2): 16-28.

A preliminary investigation of the region using the 1:2,000,000 Atlas of Geology and Geophysics of the South China Sea shows that seven tectonic cycles, involving continental breakup, orogenesis, subduction, and collision during various periods since the Proterozoic, have shaped the area. The northwest portion of the region is a microplate mosaic of Proterozoic-Paleozoic continental crust, the central part is an extensional area of oceanic crust formed during the late Mesozoic--Cenozoic, and the southeast and east are a complex, convergent area of Late Mesozoic intermediate type crust. Since the Cre- taceous, as a result of the breakup of the Eurasian Plate, seafloor spreading, drift, convergence, and rotation of blocks, the sea itself has evolved as a marginal sea. 2nd Mar. Geol. Invest. Brigade, Min. of Geol. and Mineral Resour., Guangzhou, People's Republic of China. (hbf)

89:3970 Kennieutt, M.C. II and J,M. Brooks, 1988. Relation

between shallow sediment bitumens and deeper reservoired hydrocarbons, offshore Santa Maria Basin, California, U.S.A. Appl. Geochem., 3(6): 573-582.


Near surface sediment bitumens collected over known production in the offshore Santa Maria Basin were shown to be similar to reservoired petroleum in the adjacent onshore. Triterpane, sterane and aro- matized sterane compositional similarities between oils and near surface sediment bitumens suggest a common source in the Monterey Formation. An empirical model based on the relation between oil composition and API gravity was applied to the near surface bitumens and accurately predicted by API gravity of the nearest known production. Geochem. and Environ. Res. Group, Texas A&M Univ., College Station, TX 77840, USA.

89:3971 Kvenvolden, K.A., 1988. Methane hydrate---a major

reservoir of carbon in the shallow geosphere? Chem. Geol., 71(1-3):41-51.

Methane hydrates are solids composed of rigid cages of water molecules that enclose methane, found in sediments under specific pressure-temperature conditions in permafrost regions and in outer continental margins. The potential amount of methane present at depths of ( 2 0 0 0 m is very large, probably on the order of l × l04 Gt of carbon. Because the estimated amount of organic carbon in the methane-hydrate reservoir is so large, methane hydrates are of interest as a potential resource of natural gas and as a source of atmospheric methane released by global warming. However, as a contributor to changing global climate, the effect of destabilized methane hydrates, particularly in the shallow nearshore region of the Arctic Ocean, will probably be minimal over the next 100 years. USGS, Menlo Park, CA 94025, USA.

89:3972 Lai, Wanzhong, 1988. Geologic-tectonic character-

istics loll oil and gas-hearing basins in the sea areas of China. Mar. Geol. Quat. Geol., 8(2):29- 36. (In Chinese, English abstract.)

The violent rifting and magmatic events which led to the formation of down-faulted basins in eastern China have also affected the offshore, where four types of sedimentary basins with distinct facies, thermodynamic regimes, tectonic histories, and oil and gas reserves are recognized. The characteristics of the petroleum reservoirs are described, and a preliminary model for the development and evolution of the basins is presented. Offshore Oil Explo- ration and Develop. Res. Centre, China Natl. Offshore Oil Corp., Xicheng, Hebei, People's Re- public of China. (hbf)

89:3973 Liu, Xingli, 1988. Migration of Cenozoic subsidence

center and its control over the distribution of hydrocarbon-hearing formations in Bohai Sea a r e a . Mar. Geol. Quat. Geol., 8(3):15-23. (In Chinese, English abstract.) Bohai Petroleum Co., Tianjin, People's Republic of China.

89:3974 Murray, T.H. Jr. et al., 1988. World energy devel-

opments, 1987. Am. Ass. Petrol. Geol. Bull., 72(10B):396pp; 34 papers.

The annual summary of world energy developments provides a record of significant 1987 activities in exploration and production in the oil and gas fields of North America and foreign countries, as well as the energy minerals--coal, oil shale, and uranium. The individual reports are based on well data, land status, production statistics, and geophysical activity information from many sources and include in- formed commentary by authors with considerable expertise in their respective areas. It is noted that there was no activity to report on the Atlantic coastal plain and outer continental shelf. (hbf)

89:3975 Schoeli, Martin, 1988. Multiple origins of methane in

the Earth. Chem. Geol., 71(1-3):1-10.

Methane occurrences in the Earth's crust are predominantly of biogenic origin, but methane can also form through inorganic reactions. Biogenic methanes form through bacterial processes which follow a CO 2 reduction and/or fermentation path- way, and by thermogenic processes, most likely involving pyrolysis of organic matter. The different character of methane in individual sedimentary basins may be a result of the geologic history. Abiogenic methane occurs in hydrothermal vents and ophiolite complexes, probably from inorganic reactions. A uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes. Chevron Oil Field Res. Co., La Habra, CA 90631, USA.

89:3976 Schoell, Martin (guest editor), 1988. Special issue.

Origins of methane in the Earth. Chem. Geol., 71(1-3):265pp; 19 papers.

This special issue combines lectures presented at a symposium of like title at the 1987 meeting of the Geological Society of America, with invited contributions in an effort to present an up-to-date reference volume on the much debated subject of the origin of methane. Included are data on all aspects


of the formation of methane--atmospheric, shallow-bacterial, commercially reservoired, and abiogenic--and the complex processes involved in its production. It is noted that although there is considerable evidence for its general origin by the conversion of organic matter within relatively shallow-seated rocks, the suggested source from within the Earth itself remains to be proven. (hbf)

89:3977 Simoneit, B.R.T., O.E. Kawka and M. Brault, 1988.

Origin of gases and condensates in the Guaymas Basin hydrothermai system (Gulf of California). Chem. Geol., 71(1-3): 169-182.

The hydrothermal system in Guaymas Basin con- verts immature organic matter in the sediment cover to petroleum (methane to asphalt), which is scav- enged by fluids and migrates upward. The more volatile and soluble hydrocarbons brought to the seabed are injected into ambient seawater, whereas the heavy ends solidify in mineral mounds at the seafloor. The water, surface sediment, and mounds all contain large concentrations of these hydrocarbons. Data from a sample suite provide an overview of the organic geochemistry of these natural gases and their condensates. Petrol. Res. Gr., Oregon State Univ., Corvallis, OR 97331, USA.

89:3978 Sweeney, R.E., 1988. Petroleum-related hydrocarbon

seepage in a Recent North Sea sediment. Chem. Geol., 71(1-3):53-64.

Data from a set of cores taken in the vicinity of a major hydrocarbon gas anomaly during a 55-day surface geochemical survey in the Norwegian Sector of the North Sea in 1985 illustrate the fate of hydrocarbon migration through unconsolidated marine sediment. Migration by bubble ebullition trans- ports hydrocarbons through the near-surface sediment producing gas plumes in the bottom water, and trapping of bubbles in the sediment may produce patchy, hydrocarbon 'anomalies.' However, extensive sediment anomalies can only form at depth below the level where sulfate is depleted from pore water, as a result of vertical migration by molecular diffusion which creates a steady-state hydrocarbon oxidation zone, efficiently eliminating further hydrocarbon transport toward the surface. UNOCAL Sci. and Tech. Div., Brea, CA 92621, USA.

D340. Manganese nodules, etc. 89:3979

Chen, Zongtuan, 1988. Analysis of resources and exploration prospect of deep-sea multimetallic

nodule and crust. Mar. Geol. Quat. Geol., 8(3): 93-102. (In Chinese, English abstract.) Inst. of Mar. Geol., Min. of Geol. and Mineral Resour., Qingdao, People's Republic of China.

89:3980 Drozdovskaya, A.A. and G.N. Orlovskiy, 1988.

Physicochemical computer modeling of the genesis of marine sedimentary ferromanganese nodules. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 294(1-6):163-167. Inst. of Geochem. and Phys. of Minerals, UkSSR Acad. of Sci., Kiev, USSR.

89:3981 Huh, C.-A., 1988. Thorium-protactinium age dating

of ferromanganese crusts. A cta oceanogr, taiwan., 20:95-106. Coll. of Oceanogr., Oregon State Univ., Corvallis, OR 97331, USA.

D360. Books, collections (general)

89:3982 Meissner, R. and D. Gebauer (eds.), 1989. Evolution

of the European continental crust: deep drilling, geophysics, geology and geochemistry. Tectono- physics, 157(1-3):219 pp; 16 papers.

These papers were presented at a special symposium held during the April 1987 meeting of the EUG in Strasbourg, and reflect the progress that has been made in European geoscience over the past decade. Ten of the contributions treat the crystalline rocks found in two of the areas targeted for continental deep drilling--the Black Forest in southwestern Germany and the northeastern Bavarian basement of the Moldanubian and Saxothuringian zones. Geochronological, geochemical, and geophysical aspects of the Oberpfalz region are discussed in a number of papers; remaining papers describe various geophysical investigations, including the Kraich- gau gravity high, laboratory experiments on ani- sotropy in an amphibolite, the Conrad discontinuity, and reflection surveys of the region. (hbf)

89:3983 Townsend, P.D. (et al., editors), 1988. Thermolu-

minescenee and electron-spin-resonance dating: Part II. Quaternary applications. 5th Interna- tional Specialist Seminar, 5-10 July, 1987, University of Cambridge, UK. Quat. Sci. Revs, 7(3-4):243-536; 48 papers.

Most of the 130 papers presented at the seminar have been published in two parts. Those dealing with methodology and archeological applications appear

OLR (1989) 36 (7) 609

in Volume 134, nos. 1/2 of Nuclear Tracks and Radiation Measurements and are only listed in this volume, which covers Quaternary applications. Papers here are divided into sections according to dating method. Research relying on thermolumi- nescence (TL) determinations includes reports on dating of loess, paleosols, quartz, partially bleached sediments, till, tephra, fluvial and lacustrine sediments, brickearth, calcite, and shells, as well as discussions on sensitivity following bleaching, effects of illumination wavelength, the plateau method, and zeroing and stability of the TL signal. The section on optical dating includes studies on quartz, feldspar, and zircon; recuperation after bleaching; and phos- phorescence. The final section on electron spin resonance (ESR) dating covers comparisons of ESR, uranium series, TL, and ~4C ages and dating of travertines, paleolithic calcite, calcretes, carbonates, marine aragonite, coral, saline sediment, shell, teeth, bone, eggshell, fault gouge, tephra, loess, volcanics, and baked rocks. (hbf)

D370. Miscellaneous

89:3984 Bond, G.C. and M.A. Kominz, 1988. Evolution of

thought on passive continental margins from the origin of gensynclinai theory (~1860) to the present. Geol. Soc. Am. Bull., 100(12):1909-1933.

The evolution of thought on passive continental margins is overviewed, emphasizing contributions from GSA publications when possible. Although early ideas were dominated by geosynclinal theory and vertical tectonics, plate tectonics was certainly anticipated, if not accepted, by certain early thinkers like Wegener. The consolidation and acceptance of plate tectonic theory marked a second phase in the continental margin dialog. The third period has involved a new and detailed look at passive margins and Proterozoic examples from continental interiors. Lamont-Doherty Geol. Observ., Palisades, NY 10964, USA. (fcs)

E. BIOLOGICAL OCEANOGRAPHY

El0. Apparatus and methods

89:3985 Andre, J.-M. and Andr~ Morel, 1989. Simulated

effects of barometric pressure and ozone content upon the estimate of marine phytoplankton from space. J. geophys. Res., 94(C1):1029-1037.

Barometric pressure and total ozone content may significantly depart from their mean climatology values; but these values are used in processing visible remote sensing data for estimation of phytoplankton pigment concentration in the upper ocean. The effect of ignoring such departures upon the retrieved concentration has been simulated for the broad oceanic range (0.015-20 rag/m3). The use of mean climatology values leads to variable misestimates of pigment content, by a factor of up to 2 in many situations, and above 2 for very low or high actual pigment content. Actual barometric pressure and ozone content values will have to be introduced in the processing of future visible sensor data in order to preserve accuracy. Lab. de Phys. et Chimie Mar., Univ. P. et M. Curie, Villefranche-sur-Mer, France.

89:3986 Goldman, N. and P.J.D. Lambshead, 1989. Opti-

mization of the Ewens/CasweH neutral model program for commqBity diversity analysis. Mar. Ecol.-Prog. Ser., 50(3):255-261.

Lambshead & Plait (1988) noted that Ewens' program presented serious computational problems which could not be effectively overcome by sub- sampling or by substitution of a simpler equitability method. In this paper a modified program is presented which greatly reduces these computational difficulties, making it suitable for personal com- puters. Zool. Dept., British Mus., Cromwell Rd., London SW7 5BD, UK.

89:3987 Hamano, Akira et al., 1988. Effects of ship motion

and survey conditions on volume back-scattering strength in acoustic survey. Nippon Suisan Gakkaishi (Bull. japan. Soc. scient. Fish.), 54(9): 1533-1543. (In Japanese, English abstract.) Shimonoseki Univ. of Fish., Yoshimi, Shimo- noseki 759-65, Japan.

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