Oceanographic Literature Review (1979) 26 (2) 65

79:470 Wakeley, J. Jr., 1978. Coherent ray tracing--

measured and predicted shallow-water frequency spectrum. J. acoust. Soc. Am., 63(6): 1820-1823.

Computer simulation employs a model of the pressure signature for an underwater explosive charge and ray- tracing techniques to predict the received energy spectrum. Applied Research Laboratory, The Pennsylvania State University, Box 30, State College, Pennsylvania, 16801, U.S.A. (swm)

18. Fluid mechanics

79:471 Balasubramanian, V. and S. C. Jain, 1978. Horizontal

buoyant jets in quiescent shallow water. J. envi- ron. Engng Div., Am. Soc. civ. Engrs, 104(EE4): 717-730.

A laboratory experiment was conducted to investigate the flow field induced by a horizontal heated jet discharged into a shallow basin. Empirical relations for flow stability and temperature changes are presente& Institute of Hydr. Research, University of Iowa, Iowa City, Iowa, U.S.A. (nrp)

79:472 Davey, M. K., 1978. Recycling flow over bottom

topography in a rotating annulus. J. Fluid Mech., 87(3): 497-520.

The effect of topography upon the flow of a homogeneous fluid in a rotating frame is investigated theoretically for systems, such as the Antarctic Circumpolar Current, in which no upstream conditions may be specified. The particular system considered is a rotating annulus of low topography with flow forced by a differentially rotating rigid lid. Solutions for flow regimes ranging from linear viscous to nonlinear quasi-inviscid are presented and compared qualitatively to experiments. National Centre for Atmospheric Research, Boulder, Colorado 80303, U.S.A. (nrp)

79:473 Linden, P. F. and T. G. L. Shirtcliffe, 1978. The dif-

fusive interface in double-diffusive convection. J. Fluid Mech., 87(3): 417-432.

A steady state theoretical model is proposed which deals with the interface in a two-layer double-diffusive system set up in a "diffusive" rather than a "fingering" configuration. Model predictions of cross interface transports and interface thickness are compared to time-dependent experiments which are considered to run down through a series of equilibrium states. Figures include a diffusive interface shadowgraph. Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, Great Britain. (nrp)

B. Chemical Oceanography

1. Apparatus and methods

79:474 Dryssen, D., O. Johansson and M. Wedborg,

(comments), S. Ben-Yaakov and E. Sass (reply), 1978. Alkalinity and total carbonate in Dead Sea brines [and] On the merit of defining and applying ionic medium activity scales. Mar. Chem., 6(3): 275-288.

79:475 Efird, K. D. and V. M. Putnam, 1978. A sea water

deaeration procedure for conducting electro- chemical experiments. Corrosion, 34(7): 250-251.

Electrochemical techniques in corrosion studies require deaeration of the electrolyte. A fast technique for seawater deaeration is described which uses sodium sulfite, catalyzed b~ cobalt, as an oxygen reactant. Occidental Petroleum Corporation, Tripoli, Libyan Arab Republic. (fcs)

79:476 Lowry, J. H. and K. H. Mancy, 1978. A rapid auto-

mated system for the analysis of dissolved total organic nitrogen in aqueous solutions. Wat. Res., 12(7): 471-475.

An automated method for analysis of dissolved organic nitrogen is described. Nitrogen-containing ultraviolet-irradiated products are reduced to ammonia which is detected by a gas-sensing probe. An irradiation period of 17 minutes allows quantitative measurement of organic nitrogen compounds common to natural waters. The University of Michigan, The Environmental Chemistry Laboratory, 2530 School of Public Health I, Ann Arbor, Michigan 48109, U.S.A. (smm)

79:477 Stepan, S. F., J. F. Smith, U. Flego and J. Reukers,

1978. Apparatus for on-site extraction of organic compounds from water. Wat. Res., 12(7): 447 -449.

A simple, portable apparatus for on-site extractions of organic compounds from water and air is described. Extraction is based on reversible sorption by Amberlite XAD-resins and Tenax-GC. On-site and laboratory extraction are compared. Department of Physical Chemistry, La Trobe University, Bundoora, 3083, Victoria, Australia.

66 Oceanographic Literature Review (1979) 26 (2)

79:478 Truesdale, V. W., 1978. The automatic determination

of iodate- and total-iodine in seawater. Mar. Chem., 6(3): 253-273.

Procedures are described for measuring iodate-iodine and total-iodine in seawater using a Technicon Auto- Analyser. Data from three hundred seawater samples from the eastern Pacific Ocean support the reliability of the method. Institute of Hydrology, Maclean Building, Crowmarsh, Wallingford, Oxon, England. (smm)

3. Composition of sea water

79:479 Bruland, K. W., G. A . Knauer and J. H. Martin,

1978. Cadmium in northeast Pacific waters. Limnol. Oceanogr., 23(4): 618-625.

Recent work suggests that cadmium concentrations have well-defined distributions in the world's oceans. Samples taken and analyzed by different methods showed a significant correlation between cadmium and both phosphate and nitrate. It is apparent that microplankton play a dominant role in its biogeochemical cycling. Center for Coastal Marine Studies, Division of Natural Sciences, University of California, Santa Cruz, California 95064, U.S.A. (swm)

79:480 Morris, P. D., K. J. R. Rosman and J. R. De Laeter,

1978. Cadmium levels in coastal and estuarine waters of western Australia. Jl R. Soc. west. Aust., 61(1): 19-23.

The stable isotope dilution technique was used and a base line value of 0.013 ppb (ag/kg) cadmium for coastal sea water was established; this result compares favorably with overseas studies. Minimal levels of contamination were caused bv industry; the nature of the environment seems to control the cadmium levels present. Department of Physics, Western Australian Institute of Technology, South Bentley, West Australia 6102.

4. Physical chemistry in sea water

79:48 I Barley, G. E. and D. Gardner, 1978, A study of

copper, lead and cadmium speciation in some estuarine and coastal marine waters. Estuar. coast, mar. Sei., 7(I): 59-70.

Changes in trace metal speciation between six different water types are reported. The analysis scheme assigns trace metals in solution to seven operationally defined species using analysis by anodic

stripping voltammetry and a combination of pretreatments by chelating resin, UV irradiation and acidification. Changes in samples with storage are also considered, and polythene was shown to prevent losses or changes in speciation. Analytical Chemistry Section, Australian Atomic Energy Commission, Lucas Heights, NSW, Australia. (djh)

79:482 Chen, Chen-Tung, A., 1978. Decomposition of

calcium carbonate and organic carbon in the deep ocean. Science, 201 (4357): 735-736.

Estimated values of the calcium variation with depth that agree with values obtained by direct measurements are used to estimate the ratio of in-situ inorganic to organic carbon fluxes in the ocean. This ratio is shown to indicate differences between water masses. School of Oceanography, Oregon State University, Corvallis 97331, U.S.A. (djh)

79:483 Elgquist, Bengt and Margareta Wedborg, 1978.

Stability constants of NaSO4, MgSO4, MgF +, and MgCI + ion pairs at the ionic strength of seawater by potentiometry. Mar. Chem.. 6(3): 243-252.

By the use and comparison of several different methods, stability constants for NaSO~, MgSO4, MgF +, and MgCI + were determined at I atm, 25°C and 0.7 M formal ionic strength. They are respectively: 1.8, 6.3, 22.9 (all +0.1), and 0.34 (~- 0.02) M 1. G6teborgs Analyslaboratorium AB, Formsk/iraregatan 9, S-412 61 G6teborg, Sweden. (fcs)

79:484 Harrison, W. G., 1978. Experimental measurements

of nitrogen [ammonium] remineralization in coastal waters. Limnol. Oceanogr., 23(4): 684-694.

Ammonium remineralization was measured directly with a N- 15 isotope dilution technique. Remineralization fluxes were high, often exceeded assimilation fluxes, and decreased with depth and distance offshore, Turnover times from three to sixteen davs were estimated for the remineralization of utilizaigle organic nitrogen. Marine Ecology Laboratory, Bedford Institute of Oceanography, Dartmouth, Nova Scotia B2Y 4A2. (izs)

79:485 Honjo, Susumu and Jonathan Erez, 1978. Dissolution

rates of calcium carbonate in the deep ocean: an in-situ experiment in the North Atlantic Ocean. Earth planet. Sci. Letts, 40(2): 287-300.

The deployment of in-situ water circulators at 3600, 4800, and 5518 m for 79 days in the Sargasso Sea allowed (I) dissolution rates to be determined (by

Oceanographic Literature Review (1979) 26 (2) 67

weight loss) for several different tests, and (2) the verification of a chemical lysocline, whose origin appears kinetic, and which varies for different particles. Dissolution rates were 4-5 times greater than reported by other workers, and normalized rates with respect to BET surface area differed by two orders of magnitude. Both these findings could be explained by the unanticipated interference of an organic coating of some kind because bleached tests of certain organisms dissolved significantly faster than unbleached tests. A simple model for different CaCO~ particles predicts the existence of only coccoliths and diatoms in the deep Atlantic, which is in good agreement with known distributions. Figs. include 13 SEM plates of carbonate particles and tests. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, U.S.A. (fcs)

79:486 Whitfield, M., 1978. The hydrolysis of ammonium

ions in sea water--experimental confirmation of predicted constants at one atmosphere pressure. J. mar. biol. Ass. U.K., 58(3): 781-787.

Recent measurements confirm earlier calculations of the extent of hydrolysis of ammonium ions in sea water over a range of temperatures and salinities. Tables of the percentage of un-ionized ammonia in sea water compiled from the calculated data can therefore be used with confidence in assessing ammonia toxicity in mariculture systems. The Laboratory, Marine Biological Association, Citadel Hill, Plymouth, Great Britain.

6. Dissolved gases

79:487 Cohen, Yuval and L. I. Gordon, 1978. Nitrous oxide

in the oxygen minimum of the eastern tropical North Pacific: evidence for its consumption during denitrification and possible mechanisms for its production. Deep-Sea Res., 25(6): 509-524.

The eastern tropical North Pacific appears to be a net source for atmospheric N20 (average flux magnitude 0.14 pg N20/cm2/s) . The first concurrent mea- surements of N20, oxygen, and nutrients suggest nitrification as the most important N20-producing mechanism. The data comprise the first set of detailed, whole water column N20 data from the Pacific. School of Oceanography, Oregon State University, Corvallis, Oregon 97331. U.S.A. (izs)

79:488 Foster, P., K. B. Pugh and D. T. E, Hunt, 1978.

Ammonia distributions in the surface waters of Liverpool Bay. Estuar. coast, mar. Sci., 7(I): 71-78.

Dissolved ammonia concentrations are reported for six surveys during which a continuous sampling system was used. In summer the distribution is biologically determined, hut during the rest of the year the dominant input of effluents from the Mersey River is dispersed by the wind-driven circulation of the bay. Marine Science Laboratories, Menai Bridge, Gwynedd, United Kingdom. (djh)

7. Organic compounds

79:489 Kattner, G. G. and U. H. Brockmann, 1978.

Fatty-acid composition of dissolved and particu- late matter in surface films. Mar. Chem., 6(3): 233-241.

Slicks from the coastal North Sea were analyzed for fatty acids in the dissolved and particulate components to help elucidate the origin and fate of surface films. Institute of Organic Chemistry and Biochemistry, University of Hamburg (F.R.G.), (fcs)

12. Radioactivity, radioisotopes, etc.

79:490 Patel, B., S. Patel and S. Pawar, 1978. Desorption of

radioactivity from nearshore sediment. Estuar. coast, mar. Sci., 7( I ): 49-58.

In Bombay harbor levels of reactor waste nuclides Cs- 137, Ce-144, and Ru-106 in the sediment have fallen exponentially since discharge was greatly reduced in 1971. Environmental factors influencing the dispersal of the nuclides are considered. Health Physics Division, Bhabha Atomic Research Center, Trombay, Bombay-400 085. India. (djh)

13. Geochemistry and biogeochemistry (see also under Submar ine Geology and Geophysics)

79:491 Bostrom, Kurt, Lars Lysen and Cynthia Moore,

1978. Biological matter as a source of authigenic matter in pelagic sediments. Chem. Geol., 23(1): I 1-20,

The origin of pelagic sediments is incompletely understood and various mixing models have been

68 Oceanographic Literature Review (1979) 26 (2)

applied to answer the question of possible sources of these metal-enriched deposits. In-place formation is discounted as a significant process and the trace element composition in the model sediments is explained by a large influx of biological material. Questions concerning the formation of manganese nodules and metalliferous shales can possibly be better understood through the use of mixing models. Department of Economic Geology, University of Lulea, 951 87 Lulea, Sweden. (bwt)

79:492 Boulegue, J., D. Renard, G. Michard, A. P. Boulad

and F. Chantret, 1978. Manganese dioxide concentrations on granite outcrops in an intertidal area (cove of Belmont, France). !1. Rapid manganese dioxide formation during the mixing of freshwater and seawater. Chem. Geol., 23(1): 41-63.

Field and laboratory observations are reported of the precipitation from manganese-rich fresh water on mixing with seawater. Co and U are enriched in the precipitate which shows preferential enrichment of U- 238. kaboratoire de G6ochimie des Eaux et l_aboratoire de G6ochimie et Cosmochimie (C.N.R.S. LA 196), Universit6 de Paris VI1, 75221 Paris Cedex 05, France. (djh)

79:493 Dymond, Jack and William Eklund, 1978. A micro-

probe study of metalliferous sediment compo- nents. Earth planet. Sci. Letts, 40(2): 243-251.

Layer-silicate aggregates, micronodules, and fish debris from the coarse fraction of metalliferous sediments of the Bauer Basin were analyzed by microprobe. Smectite dominates (70%). Diagenetic models (particularly to explain rare earth abundances) are discussed. Figs. include 8 mineral micrographs. School of Oceanography, Oregon State University, Corvallis, Oregon 9733 I, U.S.A. (fcs)

79:494 Martens, C. S., R. A. Berner and J. K. Rosenfeld,

1978. Interstitial water chemistry of anoxic Long Island Sound sediments. I!. Nutrient regeneration and phosphate removal. Limnol. Oceanogr., 23(4): 605-617.

Nutrient regeneration stoichiometry is studied using concentration vs. depth profiles of dissolved sulfate, ammonia, reactive phosphate, and other chemical species. Possible phosphate removal in rapidly depositing organic-rich sediments by authigenic mineral precipitation, and the effects of differential diffusion and adsorption of ammonia and phosphorus are discussed. Department of Geology and Geo- physics, Yale University, New Haven, Connecticut 06520, U.S.A. (izs)

79:495 Morse, J. W. and Neil Cook, 1978. The distribution

and form of phosphorus in North Atlantic Ocean deep-sea and continental slope sediments. Limnol. Oceanogr., 23(4): 825-830.

The purpose of this study was to clarify the forms, chemical associations, and diagenetic processes of phosphorus in marine sediments- all necessary in understanding the overall phosphorus cycle. Apatite P is most abundant, with distributions paralleling those of calcium carbonate. Other inorganic P is associated with acid-leachable Fe and Mn. Organic P (associated with organic C) is most abundant in reducing environments on the continental slope. Division of Marine and Atmospheric Chemistry, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida 33149, US.A. (fcs)

79:496 Peters, K. E., R, E. Sweeney and I. R. Kaplan, 1978.

Correlation of carbon and nitrogen stable isotope ratios in sedimentary organic matter. Limnol. Oceanogr., 23(4): 598-604.

While both nitrogen and carbon isotopic ratios have been used to estimate the relative contributions of marine and terrestrially derived organic matter, the technique has been limited by variation of these ratios in source material, Using both ratios together allows more conclusive differentiations, at least insofar as a linear correlation of ratios has been established in the northeast Pacific. However, anomalous source areas (marine or terrestrial) will not fit the model. Department of Earth and Space Sciences, and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, 90024, U.S,A. (fcs)

79:497 Valiela, ivan, .I. M. Teal, Suzanne Volkmann,

Deborah Shafer and E. J. Carpenter, 1978. Nutrient and particulate fluxes in a salt marsh [Great Sippewissett Marsh, Falmouth, Massa- chusetts] ecosystem: tidal exchanges and inputs by precipitation and groundwater. Limnol. Oceanogr., 23(4): 798-812.

Consideration of a salt marsh nitrogen budget reveals: (1) a net annual export of ammonium, nitrate, nitrite, DON, PN, PC, and phosphate: (2) ammonium, DON, and PN as the major N species exported: (3) a net nutrient import in summer; and (4) an increased ammonium export in August. Groundwater provides primarily NO3-N and DON; precipitation, DON, NO3-N, and NH4-N. Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, U.S.A. (izs)

Oceanographic Literature Review (1979) 26 (2) 69

79:498 White, A. F., 1978. Sodium coprecipitation in calcite

and dolomite. Chem. Geol., 23(I): 65-72. Department of Geological Science, North- western University, Evanston, Illinois 60201, U.S.A.

79:499 Williams, S. C.. H. J. Simpson, C. R. Olsen and

R. F. Bopp, 1978. Sources of heav~ metals in sediments of the Hudson River Estuary. Mar. Chem.. 6(3): 195-213.

Concentrations, sources, and contamination patterns are discussed for various heavy metals fl)und in the sediments of the Hudson River. Lederle Laboratory of American Cyanamide, Spring Valley, N. Y. U.S.A. (s~,m)

15. Corrosion

79:500 Money, K. L. and W. W. Kirk, 1978. Stress corrosion

cracking behavior of wrought Fe-Cr-Ni alloys in marine atmosphere. Mater. Perform., 17(7): 28-36.

Results of a five-year test on susceptibility of Fe-Cr- Ni steels exposed to a marine atmosphere are reported. The International Nickel Company, Inc., Francis L. LaQue Corrosion Laboratory, Wrights- ville Beach, North Carolina, U.S.A. (swm)

17. Pollut ion (see also under Biological Ocean- ography and General)

79:501 Bocard, C., C. Gatellier et Ph. Renault, 1978.

Le petrole et son 6volution apres un 6pandage accidentel en mer. 1. L'6volution primaire. ]Oil and how it evolves after an accidental offshore spill, i. Primary evolution.] Revue Inst. ft. P~trole, 33(3): 349-366.

This paper reviews the physical processes, including evaporation, dissolution, dispersion, and sedimen- tation, which affect the fate of petroleum spilled at sea during the first few days immediately after the spill. lnstitut Francais du P6trole, I e t 4, av. de Bois-Pr~au, BP 311, 92506 RueiI-Malmaison Cedex, Paris, France. (bwt)

79:502 Middleditch, B. S., Brenda Basile and E. S. Chang,

1978. Discharge of alkanes during offshore oil production in the Buccaneer Oilfield. Bull. environ. Contamin. Toxicol., 20(1): 59-65.

in this report (part of a multidisciplinary study of an active oilfield), the mean discharge rate of C~2-Ca~ alkanes in the discharged brine from offshore production platforms was 191 g/day. Additional research is suggested to determine alkanes' dispersion rate, pool size, and relationship to alkanes of biogenic origin. Department of Biophysical Sciences, University of Houston, Houston, Texas 77004, U.S.A. (smf)

79:503 Skei, J. M., 1978. Serious mercury contamination of

sediments in a Norwegian semi-enclosed bay [Gunnekleivfjordenl. Mar. Pollut. Bull., 9(7): 191-193.

A probable accumulation often tons of mercury in the upper 5 cm sediment laver o fa 1 kin" bay is attributed to 25 years of inorganic mercury discharge from a chlor-alkali plant. Norwegian Institute for Water Research, Postboks 333, Blindern, Oslo 3, Norway. (smfl

18. Particulate matter

79:504 Hoskin, C. M., D. C. Burrell and G. R. Freitag, 1978.

Suspended sediment dynamics in Blue Fjord, western Prince William Sound, Alaska. Estuar. coast, mar. Sci., 7(I): 1-16.

A detailed survey of the distribution of sediments carried into a fjord by glacier meltwater is reported. The study includes sediment trap collection of sediments in the water column as well as measurements of bottom sediment composition and accumulation rates. Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99701, U.S.A. (djh)

79:505 Siezen, R. J. and T. H. Mague, 1978. Amino acids in

suspended particulate matter from oceanic and coastal waters of the Pacific. Mar. Chem., 6(3): 215-231.

Hydrolyzed particulate matter was analyzed by gas- liquid chromatography for concentrations of 15 amino acids glycine, serine, glutamic acid, and aspartic acid were the most abundant offshore. Total particulate amino acid concentration decreases offshore (highest coastal values of 2260 nmoles/I, lowest oceanic values of 90 nmoles/1), and decreases with depth, leveling off at 10-40 nmoles/I at 200 m. Values are related to N and C concentrations and to protein equivalents. Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine 04575, U.S.A. (fcs)

70 Oceanographic Literature Review (1979) 26 (2)

79:506 Smetacek, V., K. von Brockel, B. Zeitzschel and

W. Zenk, 1978. Sedimentation of particulate matter during a phytoplankton spring bloom in relation to the hydrographical regime. Mar. Biol., 47(3): 211-226.

Processes which regulate the flux of particulate organic matter to the sea floor are a fundamental aspect of water column-sediment coupling. Sedimentation rates at different depths were recorded with multisample sediment traps, and distinct compositional differences in material collected indicate phases of a progressively deteriorating phytoplankton population. Quantifying and qualifying the organic matter that settles out of the euphotic zone to the bottom will be of vital importance to all research done at the benthic boundary layer. Institut fiir Meereskunde an der Universit~it Kiel, Kiel, Germany (FRG). (bwt)

79:507 Trent, J. D., A. L. Shanks and M. W. Silver, 1978.

In-situ and laboratory measurements on macro- scopic aggregates in Monterey Bay, California. Limnol. Oceanogr., 23(4): 626-635.

Collecting and field measurement techniques for fragile macroscopic aggregates (marine snow) are described. Based on three years of underwater observations, which document the frequent occurrence of these organic aggregates in a neritic environment, their size, distribution, chlorophyll a and pheopigment concentrations are reported. Center for Coastal Marine Studies, University of California, Santa Cruz. California 95064, U.S.A. (izs)

19. Miscel laneous

79:508 Benzhitskij, A. G., L. V. Tretjakova and E. A. Koles-

nikova, 1978. Oil aggregates in hyponeuston of the eastern Atlantic. (In Russian.) Gidrobiol. Zh., 14(3): 53-56.

Surface distribution of oil aggregates in the eastern Atlantic from north of the Canary Islands to the Equator is described: oil aggregate concentration decreased from north to south. A specific neustonic periphyton on the aggregates is described.

79:509 Meyers, P. A. and T. G. Oas, 1978. Comparison of

associations of different hydrocarbons with clay particles in simulated seawater. Environ. Sci. Technol., 12(8): 934-937.

In order to help predict the fractionation of petroleum components in marine waters caused by selective sorption on clay minerals, the association of various

hydrocarbons and smectite clay in salt solutions was investigated in the laboratory. Among many findings, the association of (1) aromatic hydrocarbons is low: (2) n-alkane association increased with carbon chain length; (3) n-eicosane and n-eicosene increased with increasing hydrocarbon concentrations. Department of Oceanography, Florida State University, Talla- hassee, Florida 32306, U.S.A. (fcs)

C. Submarine Geology and Geophysics

1. Apparatus and methods

79:510 Horsfall, J. A. C. and G. C. P. King, 1978.

A new geophysical tiltmeter. Nature, Lond., 274(5672): 675-676. Department of Geodesy and Geophysics, Madingley Rise, Madingley Road, Cambridge, United Kingdom.

79:511 Pil'nik, G. P., 1977. Astronomical time determination

and continental drift. Phys. solid Earth (a trans- lation ofFiz. Zemli), 13(7): 449-453.

The most accurate observations of the International Time Service for the period 1968-1974 are analyzed. It is shown that the accuracy of the contemporary astronomical time measurements is inadequate for the study of continental drift. In the measurements carried out with two instruments, at the same observatory, the periodic errors are appreciably different. Therefore, one should be extremely cautious in using astronomical measurements for the study of the movement of continental blocks. P. K. Shternberg, State Astronomical Institute, U.S.S.R.

79:512 Sebulke, J., 1978. The theoretical investigation of

resistivity methods for geoelectrical prospecting in marine areas. J. Geophys., 44(3): 245-255.

The applicability of the geoelectrical resistivity method in marine areas is studied by model calculations. For a simplified three-layer model assuming homogeneous and isotropic conditions together with parallel boundaries the apparent resistivity is calculated for three different electrode configurations. It is concluded that for two of the configurations the thickness of layer 2 (sediments) can be determined with sufficient accuracy. Technische U niversit/it Berlin, Institut fiir Angewandte Geophysik, Petrologie und Lagerst/ittenforschung, Strasse des 17, Juni 135, EB 15, 1000 Berlin 12, Germany.