(Sites 908–909), Yermak Plateau

Thiede, J., Myhre, A.M., Firth, J.V., Johnson, G.L., and Ruddiman, W.F. (Eds.), 1996Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 151

8. PLANKTONIC FORAMINIFER CENOZOIC BIOSTRATIGRAPHY OF THE ARCTIC OCEAN,FRAM STRAIT (SITES 908-909), YERMAK PLATEAU (SITES 910-912),

AND EAST GREENLAND MARGIN (SITE 913)1

Dorothee Spiegler2

ABSTRACT

The resolution of a planktonic foraminifer Cenozoic biostratigraphy in the Greenland Sea and in the Arctic Ocean is quitelow, because of the scarcity of calcareous microfossils and the low diversity of assemblages. The Neogloboquadrina pachy-derma sin. Zone spans the entire Quaternary, whereas the Neogloboquadrina atlantica Superzone occupies the Pliocene andparts of the upper Miocene. Biogenic ice-rafted debris such as Inoceramus-púsms, indicative of glacial conditions, are firstdocumented during the late Pliocene at the Fram Strait sites and at the Yermak Plateau. Conversely, brief warm-temperate tosubtropical surface-water ingressions, documented by the occurrence of single specimens of Menardella menardii, M. limbata,Globigerinoides ruber, Gls. conglobatus, Gls. extremus, Gls. trilobus, Globigerinella aequilateralis, Sphaeroidinellopsis sp.juv., aff. S. paenedehiscens, and Dentoglobigerina altispira are observed locally at the Yermak Plateau in the upper Pliocenesequence. Surface-water exchange to the north is documented by the occurrence of the Pacific planktonic foraminifer Neoglo-boquadrina asanoi in upper Pliocene sediments at the Fram Strait. Rare occurrences of planktonic foraminifers in Miocene andPaleogene sediments prevent the construction of a zonation.

INTRODUCTION

Seven sites (Sites 907-913) were drilled during Ocean DrillingProgram (ODP) Leg 151. The sites were located in four regions to in-vestigate the paleoceanography and paleoclimatology of the northernhigh latitudes (Fig. 1). A north-south transect was drilled involvingSites 908 through 912. Site 911 with three holes drilled (between80°28.466'N-80°28.485'N and 8°13.636'E-8°13.640'E) is the mostnortherly site. Site 908 with Hole 908A (78°23.112'N; 1°21.637'E)and Hole 908B (78°23.125'N; 1°21.644'E) is the most southerly tiepoint in this transect. The study of planktonic foraminifers encoun-tered in the sediments at these five sites is the main objective of thispaper. The biostratigraphy of Site 913, drilled in the Greenland Ba-sin, is also studied by means of planktonic foraminifers. Site 907,drilled on the eastern Iceland Plateau, is not considered in this study.

Generally, at the northern high latitudes most of the samples arepoor in planktonic foraminifers or barren, owing to cold-water tem-peratures and/or dissolution of the calcareous microfossils. Anotherfactor is dilution by high amounts of detrital material and ice-rafteddebris (IRD).

The high-latitude planktonic foraminifer associations are low di-versity faunas composed of long-ranging species. The standard zona-tions established for low latitudes (Blow, 1969, 1979; Bolli andSaunders, 1985), and for northern temperate regions (Berggren,1972; Poore and Berggren, 1975; Poore, 1979; and Weaver andClement, 1986) are generally not applicable because the index fossilsused for these zonal definitions are often absent in high latitudes.Only in a few short Neogene intervals at the investigated sites do sin-gle observations of immigrant warm-adapted species of planktonicforaminifers allow a rough correlation to the above-mentioned zona-tions. Studies of the Leg 104 sites in the Norwegian Sea have pro-

Thiede, J., Myhre, A.M., Firth, J.V., Johnson, G.L., and Ruddiman, W.F. (Eds.),1996. Proc. ODP, Sci. Results, 151: College Station, TX (Ocean Drilling Program).

2GEOMAR, Research Center for Marine Geosciences, Wischhofstraße 1-3, D-24148 Kiel, Federal Republic of Germany, [email protected]

duced a local high-latitude Neogene zonation (Spiegler and Jansen,1989), which is more useful for the interpretation of the Leg 151 data.

METHODS

Stratigraphic results and paleotemperature estimations for Leg151 were obtained by the investigation of planktonic foraminifersfrom about 1400 samples. Samples were taken from the core catchersand from the calcareous sediments. About one 20-cm3 sample persection of core was used. The preparation methods used to obtain for-aminifers differed depending on the degree of sediment induration.Soft sediments were washed over a 63-µm screen. Slightly induratedsediments were soaked in diluted H2O2 solution and then wet sieved.Indurated samples were freeze-dried, soaked in hot paraffin, andboiled in a soda lye solution until disintegration occurred. This meth-od was repeated until a reasonable amount of loose particles was ob-tained. Range tables summarize the main characteristics used forplanktonic foraminiferal studies (Tables 1-11).

PLANKTONIC FORAMINIFER BIOSTRATIGRAPHY

The Neogloboquadrina pachyderma sin. Zone spans the entireQuaternary. The nearly monospecific association of N. pachydermasin. shows highly variable abundances, ranging from several periodscontaining a hundred thousand specimens in 10-cm3 sediment to in-tervals barren of planktonic foraminifers (Myhre, Thiede, Firth, et al.,1995). Such alternations seem to be typical of the changes betweenglacials and interglacial conditions, as absolute abundances of plank-tonic foraminifers correlate best with surface seawater temperaturescalculated from oxygen isotopes (Paul, 1992).

The Neogloboquadrina atlantica Superzone is defined by therange of the zonal marker, spanning the whole Pliocene and reachinginto the late Miocene. Using the change in coiling direction, localzones are defined (Weaver and Clement, 1986; Spiegler and Jansen,1989). The last occurrence of N. atlantica marks the Quaternary/Pliocene boundary, whereas the Pliocene/Miocene boundary cannotbe defined in high latitudes by planktonic foraminifers.

153

D. SPIEGLER

100°W 100° E

4040°

20° W 20° E

Figure 1. Location map of Sites 908 through 913.

The Miocene and Eocene sediments in the area of investigationcontain only some spot observations of planktonic foraminifers. Noplanktonic foraminifers were found in Oligocene sediments.

YERMAK PLATEAU

The Yermak Plateau extends for about 400 km in a north-north-west direction from the shelf of Svalbard into the Arctic Ocean. Thearea is well suited for paleoceanographic analysis of Pliocene/Qua-ternary glacial/interglacials and the preglacial conditions. A north-south transect was drilled across the plateau with Site 911 in thenorth, Site 912 in the south, and Site 910 between.

Site 911

Site 911 was the most northerly site drilled during Leg 151 and islocated on the southeastern part of the Yermak Plateau, 35 km east-northeast of Site 910. It was drilled in about 900-m water depth onthe upper slope toward the Nansen Basin, at approximately80°28.5'N, 8°13.6'E. The biostratigraphic results obtained by the in-vestigation of planktonic foraminifers are based on Hole 911A (Table1). Down to 505 meters below seafloor (mbsf), 342 samples (one persection) were analyzed. Planktonic foraminifers occurred in the Qua-

ternary section in 62% of the samples, and foraminifers are rare in thePliocene sequences, where only 23% of the samples contained plank-tonic foraminifers. Hole 911A reached Miocene sediments.

The Quaternary/Pliocene boundary is defined by the last observa-tion of Neogloboquadrina atlantica in dextral coiling direction inSample 151-911A-25X-1, 112-115 cm (227.52 mbsf), which is situ-ated just above the paleomagnetic Chron C2n, the Olduvai Event(Myhre, Thiede, Firth, et al., 1995), at approximately 1.7 Ma.

In the 228-m-thick Quaternary sequence the associations ofplanktonic foraminifers of low diversity show highly variable abun-dances. Such alternations seem to be typical of the changes betweenglacial and cold (interglacial) conditions. The assemblages consistmainly of Neogloboquadrina and Globigerina taxa, dominated by thepolar N. pachyderma sin. Ice-rafted Cretaceous Inoceramus-púsmsare found in the sediments between 35.66 and 47.50 mbsf, at 114.03mbsf, from 128.30 to 129.80 mbsf, and at 171.25 mbsf. Rare occur-rence of temperate-adapted Orbulina universa, Globoconella inflata,and Globorotalia scitula in the sequence from 144.06 to 145.56 mbsfand a single observation of Globigerinoides ruber at 194.95 mbsfdocument the fact that temperate to warm surface water sporadicallyreached into high latitudes. The single presence of these indices maybe related to short warmer episodes, not long enough to produce richand well-diversified assemblages. Therefore, at Site 911 the wholeQuaternary may be characterized generally as cold. A sequence of

154

PLANKTONIC FORAMINIFER CENOZOIC BIOSTRATIGRAPHY

Table 1. Distribution of planktonic foraminifers in Hole 911A.

Core, section,interval (cm)

151-911A-1H-1,26-281H-1, 116-1191H-2, 11-1141H-3, 30-331H-3, 110-1131H-4, 110-112 to1H-5, 115-118 to1H-CC2H-1, 119-124 to2H-3, 119-1242H-4.119-1242H-6, 119-1242H-CC3H-1, 119-1223H-2, 119-122 to3H-5, 119-1223H-6, 119-122 to4H-1, 116-119 to4H-4, 116-118 to5H-1, 120-124 to5H-3.120-1245H-4, 120-1245H-5, 120-124 to6H-6, 120-1246H-CC7H-1, 120-1247H-2, 120-124 to7H-CC8H-1, 119-1228H-2, 119-122 to8H-5, 119-122 to8H-CC to9H-3, 120-1249H-3, 130-13411H-1, 130-134 to11H-4, 130-13411H-5.130-13411H-CC12H-1, 112-11612H-2, 112-11612H-3, 112-116 to12H-5, 112-11612H-6, 111-118 to13H-1, 115-12013H-3, 115-12013H-4, 115-12013H-5, 115-12013H-6, 115-12013H-CC14H-1, 115-120 to14H-4, 115-12014H-7, 115-12014H-CC to15H-5, 112-11715H-CC16X-1, 116-12016X-2, 126-12016X-3, 116-12016X-4, 116-12016X-5, 116-120 to17X-4, 115-11717X-CCto18X-3, 114-11818X-4, 114-11818X-CCto19X-4, 115-117 to19X-CC20X-1, 114-118 to20X-4, 114-118 to21X-1, 105-11021H-2, 105-110 to21X-5, 105-11021X-6, 84-89

Depth(mbsf)

0.261.162.603.304.105.607.159.50

10.6913.6915.1918.1919.0020.1921.6926.1927.6929.6634.1639.2042.2043.7045.2056.2057.0058.2059.7065.2066.3967.8972.3974.7078.0078.1095.0099.50

101.00101.90103.02104.52106.02109.02110.51112.55115.55117.05118.55120.05120.90122.05126.55129.80130.40137.52139.90141.06142.56144.06145.56147.06155.05159.00163.14164.38168.60174.25176.30179.44183.94188.95190.45194.95196.24

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Table 1 (continued).


21X-CC22X-1, 113-117 to22X-3, 116-120 to23X-2, 223-227 to24X-3, 115-11924X-6, 115-119 to

25X-1, 112-115

25X-2, 112-1525X-3, 112-115 to27X-1, 113-11827X-2, 113-11827X-3, 113-11827X-5, 113-118 to28X-2, 113-11828X-3, 109-115 to28X-6, 114-11928X-7, 1-3 to28X-CC29X-2, 110-113 to30X-5, 98-10130X-CC to31X-4, 116-12031X-5, 120-12231X-6, 120-12231X-CCto32X-3, 115-12032X-4, 117-122 to33X-4, 115-11933X-CC to34X-2, 113-11734X-3, 113-11734X-4, 113-11734X-5, 113-117 to34X-CC

35X-1, 114-117 to36X-3, 115-119 to47X-6, 121-125 to50X-2, 115-11950X-3, 115-119 to51X-CC

52X-2,52X-3,52X-4,52X-6,53X-2,53X-3,53X-3,53X-4,53X-4,53X-5,53X-5,53X-5,

115-119115-119115-119115-119 to113-11733-38113-11733-38113-11762-6784-89111-113

53X-5, 113-11753X-6, 31-3653X-6, 113-117 to53X-CC

Depth(mbsf)

197.50198.63201.59208.33219.85223.39

227.52

229.02230.52246.93248.43249.93251.61258.13259.59264.14264.51265.10267.23281.58284.30289.96291.50293.00294.00298.15299.67309.25313.30315.93317.43318.93320.25322.90324.04336.71446.27469.85471.35486.50

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Notes: The state of preservation of the planktonic foraminifers is described as G = good (little or no fragmentation, overgrowth, and/or dissolution), M = moderate (some signs of frag-mentation, overgrowth, and/or dissolution), and P = poor (severe fragmentation, heavy overgrowth, and/or dissolution). The abundances are categorized as A = abundant (morethan 25 specimens), C = common (5-24 specimens), and R = rare (less than 5 specimens). Barren (B) sequences are marked with a stipled signature. #1 = upper Neogloboquad-rina atlantica dextral, #2 = upper Pliocene.

156


7.55 m barren of planktonic foraminifers separated the fossiliferousQuaternary and the Pliocene, containing foraminifers.

The Pliocene sediments of Hole 911A are extremely poor inplanktonic foraminifers. Large parts of the sequence are almost bar-ren or contained no age diagnostic planktonic foraminifers. Becauseof these difficulties, a clear subdivision of the 275-m-thick Pliocenesequence is impossible. The uppermost sample of the Pliocene se-quence, Sample 151-911A-25X-1, 112-115 cm, contains Globiger-inoides ruber and Neogloboquadrina atlantica dextral. The latterspecies is indicative of the Neogloboquadrina atlantica dextral Zoneof the latest Pliocene (Spiegler and Jansen, 1989). Down to 318.93mbsf (Sample 151-911A-34X-4, 113-117 cm), only a few samplesyielded N. atlantica in its sinistral or dextral coiling mode. These rareoccurrences do not allow the distinguishing of zones by coiling direc-tion. Spheres of amber indicate reworking down to 365.44 mbsf, andice-rafted Inoceramus-pnsms down to 318.93 mbsf document glacialconditions back into the late Pliocene. The sediments below 318.93mbsf down to 335.23 mbsf contain no age diagnostic fossils. FromSample 151-911A-36X-3, 115-119 cm, at 336.71 mbsf, down toSample 151-911A-53X-5, 111-113 cm, at 502.29 mbsf, the sedi-ments contain N. atlantica sin., which is indicative of the Neoglobo-quadrina atlantica sin. Zone, spanning Pliocene to latest Miocene(Spiegler and Jansen, 1989). The last observations of Globigerinapraebulloides in Sample 151-911A-52X-2, 115-119 cm, at 488.40mbsf, and a single specimen of Paragloborotalia continuosa in Sam-ple 151-911A-52X-4,115-119cm, at 491.40 mbsf, indicate Plioceneto Miocene age. On the V0ring Plateau the LO (last occurrence) of P.continuosa is not younger than 4.7 Ma (Spiegler and Jansen, 1989).Miocene is confirmed in Sample 151-911A-53X-5, 113-117 cm, at502.31 mbsf, by the co-occurrence of N. pachyderma dextral, Globi-gerina praebulloides, G. officinalis, Globorotalia cf. zealandica,Catapsydrax unicavus, Paragloborotalia continuosa, and P. acos-taensis. According to Kennett and Srinivasan (1980 and 1983), P.continuosa intergrades with N. pachyderma in late Miocene to earlyPliocene in temperate to polar regions. The last 3 m of the cored sed-iment are barren in planktonic foraminifers.

Site 910

Site 910 is located on the summit of the central inner Yermak Pla-teau and is the shallowest site of the drilled transect. Holes 910A-910D were drilled in 556 m water depth at approximately 80°15.8'N,6°35.4'E. The biostratigraphic results are largely based on Hole 910C(Table 2) and were completed with the results of Hole 910D (Table3). Holes 910A and 910B stopped in Quaternary sediments, reachingonly 34.0 mbsf and 15.6 mbsf, respectively. We analyzed 191 sam-ples from Hole 910C (down to 507 mbsf) and 58 samples from Hole910D (5.80 through 156.30 mbsf). Planktonic foraminifers occurredin 63% of the samples from Hole 910C and in 38% of the samplesfrom Hole 910D. All 25 analyzed samples from Hole 910A (Table 4)contain abundant and well-preserved planktonic foraminifers of Qua-ternary age.

Nearly monospecific associations of the polar N. pachyderma sin.characterize the upper part of the Quaternary sequence. The assem-blages also sporadically contain specimens of N. pachyderma in itsdextral coiling mode, the five-chambered N. cf. dutertrei, and smallGlobigerina cf. bulloides. Below 35.30 mbsf, the lower sequence ofthe Quaternary in Holes 910C and 910D is extremely poor or barrenof planktonic foraminifers. Ice-rafted Inoceramus-púsms are foundat several levels in the Quaternary. Consequently, during the wholeQuaternary, the surface-water masses at Site 910 may be character-ized as cold.

The Quaternary/Pliocene boundary is well documented in Core151-910D-10X: the base of the N. pachyderma sin. Zone (Quaterna-ry) lies in Sample 151-910D-10X-2, 75-77 cm, at 76.35 mbsf, andPliocene is documented in Sample 151-910D-10X-3, 74-76 cm, at

77.84 mbsf by a small (350 µm in diameter) juvenile or immatureSphaeroidinellopsis sp., aff. S. paenedehiscens (Blow). Bolli andSaunders (1985) placed S. paenedehiscens within the S. seminulinaplexus. Weaver and Clement (1986) dated the LO of S. seminulinawith 3 Ma. Therefore, if the observed specimen of Sphaeroidinellop-sis sp. is not reworked, parts of the upper Pliocene may be missing.The planktonic foraminifer Zone N21 (Blow) can be determined inthe Samples 151-910D-10X-3, 74-76 cm, 151-910D-15X-3, 74-76cm, and 151-910D-16X-2, 74-76 cm. The co-occurrence of Me-nardella limbata (N12 to Recent), Dentoglobigerina altispira (N4Bto N21, LO 2.95 Ma), Globorotalia dutertrei, which starts in N21,and Globigerinoides extremus (N16 to N21) is indicative. Below 153mbsf in Hole 910D, down to 504 mbsf in Hole 910C, the entire se-quence is assigned to the Neogloboquadrina atlantica sinistral Zoneof the Pliocene. Further stratigraphic subdivision is impossible be-cause of the scarcity of the assemblages. Ice-rafted Inoceramus-prisms are documented down to 178.9 mbsf (Sample 151-910C-19R-CC).

The spot observations of the above-mentioned subtropical towarm-temperate planktonic foraminifers are indicative for severalshort, distinct, warm to subtropical surface-water ingressions duringthe generally cold late Pliocene. The topmost Pliocene sequence atSite 910 (Samples 151-910D-10X-3, 74-76 cm, and 10X-CC) con-tains assemblages with N. pachyderma dextral, Sphaeroidinellopsissp., Globigerinoides trilobus, and Turborotalita quinqueloba, indi-cating warm surface water. The downhole 41 m of sediment (down to124.74 mbsf in Hole 910D) is barren of planktonic foraminifers, ex-cept Samples 151-910D-13X-2, 74-76 cm, and 14X-2, 74-76 cm,which contain Globigerinella aequilateralis. The latter species alsocharacterize temperate surface-water masses. The most distinctwarm-water assemblages are documented in Samples 151-910D-15X-2, 74-76 cm, 16X-2, 74-76 cm, 16X-3, 74-76 cm, and 16X-3,74-76 cm. Menardella menardii, M. limbata, Neogloboquadrina du-tertrei, Dentoglobigerina altispira, Globogerinoides ruber, Gls. con-globatus, Gls. extremus, and Gls. trilobus indicate subtropical sur-face-water temperatures. These warm intervals lie in a sequencemainly barren of planktonic foraminifers that contains ice-rafted In-oceramus-pnsms and assemblages of cold-adapted benthic foramin-ifers. Therefore, the climatic scenario in the area of investigation maybe interpreted as containing episodic ingressions of warm and sub-tropical surface-water masses into a generally cold ocean during thelate Pliocene. The cold conditions of the late Pliocene are further doc-umented by N. pachyderma sin. in Cores 151-910D-17X and 18X. InSample 151-910D-18X-2, 74-76 cm, N. pachyderma sin. occurs to-gether with N. atlantica sin., indicative of northern high latitudePliocene and late Miocene (Spiegler and Jansen, 1989).

Site 912

Site 912 is located on the southwestern part of the Yermak Pla-teau, 45 km southwest of Site 910. Three holes were drilled on theslope toward the Molloy Rift and the Spitsbergen Fracture Zone inabout 1037 m water depth at approximately 79°57.5'N, 5°27.4'E. Allholes had to be abandoned because of advancing ice. Hole 912A pen-etrated 145.4 m of sediment, reaching the top of the Pliocene se-quence. Hole 912B drilled only 40.5 m into Quaternary sediments,and Hole 912C was stopped at 209.1 mbsf in the Pliocene sequence.

Planktonic foraminifer biostratigraphy of Site 912 is based on theexamination of all core-catcher samples from Hole 912A (Samples151-912A-1H-CC through 15X-CC; Table 5), Hole 912B (Samples151-912B-1H-CC through 5H-CC; Table 6), and Hole 912C (Sam-ples 151-912C-1R-CC through 12R-CC; Table 7). Six additionalsamples were analyzed from Cores 151-912A-15X to study the Qua-ternary/Pliocene boundary and three samples from Core 151-912C-12X to examine the fossil content of the Neogloboquadrina atlanticasin. Zone.

157

D. SPIEGLER

Table 2. Distribution of planktonic foraminifers in Hole 910C.


151-910C-lR-1,0-31R-I,64to2R-1,68-732R-CC to5R-2, 38-425R-CC6R-CC7R-CC

8R-CC9R-CC to10R-CC11R-CC12R-CC to16R-CC

17R-1, 99-103 to20R-1, 69-72 to20R-5, 69-7220R-CC21R-1, 42^1421R-CC22R-1,99-10322R-2, 100-103 to23R-4, 97-10223R-5, 97-10223R-CC24R-1, 82-85 to25R-CC to33R-1, 102 104 to34R-1, 110-11434R-2, 110-114 to34-CC35R-1, 115-11935R-2, 115-11935R-3, 115-11935R-4, 115-11935R-5, 115-119 to36R-3, 100-184 to38R-2, 42^7 to44R-5, 110-11444R-6, 109-11344R-CC45R-1, 100-10345R-2, 100-10345R-3, 100-10345R-4, 99-102 to49R-2, 118-122 to53-CC

Depth(mbsf)

0.000.649.18

17.4037.1844.9054.5064.20

73.8083.4093.10

102.80112.40150.90

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Planktonic foraminifers are abundant and well preserved in theupper sequence of the Quaternary sediments and occur sporadicallyin the downhole sequence. Monospecific Neogloboquadrina pachy-derma sin. assemblages indicate Quaternary age for Cores 151-912A-1H through 3H, and 912B-1H through 4H. Core-catcher sam-ples from Cores 151-912A-4H through 15X are barren with the ex-ception of a single specimen of N. pachyderma sin. in Sample 151-912A-7H-CC. Cores 151-912A-12X and 14X have no recovery. Sixadditional samples from Core 151-912A-15X were processed to de-fine the boundary between the Quaternary and the Pliocene. Samplesfrom Sections 151-912A-15X-1, 15X-2, and 15X-4 are barren. Sam-ples from Sections 15X-3 and 15X-5 contain N. pachyderma sin., in-dicating a Quaternary age. Sample 151-912A-15X-5, 33-37 cm, hasthe dextral coiling juvenile Neogloboquadrina, similar to the se-

quence observed at Site 910, where they were observed in the upper-most Pliocene. Sample 151-912A-15X-CC is barren. In the lower-most part of the sequence at Site 912, planktonic foraminifers fromCore 151-912C-12R indicate the presence of the Pliocene Neoglobo-quadrina atlantica sin. Zone.

Ice-rafted Inoceramus-^xisras (Cretaceous) are found in Quater-nary sediments of Hole 912A and in Samples 151-912C-4R-CCthrough 11R-CC in Pliocene sediments.

FRAM STRAIT

The opening of the Fram Strait induced deep-water exchange be-tween the Arctic and the Atlantic Oceans and forced long-term paleo-

158


Table 3. Distribution of planktonic foraminifers in Hole 910D.


151-910D-1H-CC to6X-1,74-766X-CC to8X-1, 74-76 to9X-2, 75-76 to10X-2, 75-77

10X-3, 74-7610X-CC11X-1, 74-76 to13X-2, 74-7613X-3, 74-76 to14X-2, 74-7614X-3, 74-76 to15X-3, 74-7615X-4, 74-76 to16X-2, 74-7616X-3, 74-76

16X-5, 74-76 to17X-2, 74-7617X-3, 74-76 to17X-6, 74-7618X-1, 74-76

18X-2, 74-7618X-3, 74-7618X-4, 74-76

Depth(mbsf)

5.8037.0445.3055.6466.7476.35

77.8483.7084.44

105.24106.74114.89116.34126.24127.74134.14135.64

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climatic changes. Therefore, knowledge of the evolution of the FramStrait is one of the keys to understanding global oceanic circulation.

Site 909

Site 909 is located in the Fram Strait, north of Hovgárd Ridge, ona small abyssal terrace in 2519 m water depth at approximately78°35'N, 3°4'E. Three holes were drilled. The investigation of plank-tonic foraminifers is based on Hole 909A (Table 8), which penetrated92.5 m sediment, and on Hole 909C (Table 9) cored from 85 mbsfinto Miocene sediments down to 1061.8 mbsf. Dissolution maystrongly affect the sediments in the Miocene sequence at this site, andthe original planktonic foraminifer assemblages are not preserved.Therefore other fossil groups need to be examined to produce a usefulbiostratigraphy. We analyzed 64 samples from Hole 909A, and 335samples from Hole 909C.

The Quaternary Neogloboquadrina pachyderma sin. Zone is doc-umented in Hole 909A from the top of the sequence down to Sample151-909A-8H-CC. The assemblages are low in diversity and domi-nated by the polar N. pachyderma sin. The planktonic foraminiferabundance varies considerably (as documented in Myhre, Thiede,Firth, et al., 1995), typifying the changes between glacial and moreinterglacial conditions. An interval barren in planktonic foraminifersseparates the Quaternary N. pachyderma sin. Zone from the PlioceneNeogloboquadrina atlantica sin. Zone. This barren interval is docu-mented in Samples 151-909A-9H-CC through 11H-CC and in Sam-ples 151-909C-1R-CC through 8R-CC. The Pliocene N. atlantica sin.

Zone is present from Samples 151-909C-9R-1, 86-88 cm, to 32R-3,28-32 cm. The first observation of ice-rafted /nocerαmMS-prisms wasin Sample 151-909C-10R-CC at 181.60 mbsf in this zone. Planktonicforaminifer species of the late Pliocene include N. atlantica sin. andNeogloboquadrina asanoi. The latter species is more common in thePacific region than in the Atlantic. A single observation of Glob-oconella inflata in Sample 151-909C-31R-3, 23-28 cm, confirms theupper Pliocene down to 377.33 mbsf. The N. atlantica Superzone,spanning Pliocene to latest Miocene (Spiegler and Jansen, 1989) isdocumented down to Sample 151-909C-32R-3, 28-32 cm at 386.88mbsf. All samples between Section 151-909C-32R-5,28-32 cm, and44R-1, 32-35 cm, are barren of planktonic foraminifers. Downhole,agglutinated foraminifers dominate the assemblages. Nevertheless,planktonic foraminifers occurred in 10% of the samples. In Sample151-909C-76R-1, 96-98 cm, at 808.56 mbsf the FO (first observa-tion) of Globigerina bulloides indicates the upper Miocene. The FOof Orbulina universa in Sample 151-909C-89R-1, 97-100 cm, at934.07 mbsf is important, because this FA (first appearance) definesa worldwide datum that coincides approximately with the beginningof planktonic foraminifer Zone N9 in the middle Miocene at 15.1 Ma.The occurrence of Globorotalia scitula (range N9 to Recent) in Sam-ple 151-909C-103R-2, 3-7 cm, at 1059.53 mbsf indicates also an ageyounger than 15.1 Ma. Therefore, the oldest fossiliferous sedimentspenetrated at Site 909 are of early middle Miocene age. Section 151-909C-103R-3 and the core-catcher sample of Core 103R are barren.Reworking is evident by abundances of megaspores in Samples 151-909C-88R-CC and 89R-2, 97-99 cm.

159

D. SPIEGLER

Table 4. Distribution of planktonic foraminifers in Hole 910A. Table 6. Distribution of planktonic foraminifers in Hole 912B.


151-910A-1H-1,24-261H-2, 24-261H-3, 4-61H-4, 8-101H-CC2H-1,20-222H-2, 20-222H-3, 20-222H-4, 20-222H-5, 20-222H-6, 20-222H-CC, 20-222H-CC3H-1, 15-193H-2, 15-193H-3, 15-193H-CC, 14-183H-CC4H-1, 13-174H-2, 24-284H-3, 13-174H-4, 4-84H-CC5X-CC, 9-135X-CC

Depth(mbsf)

0.241.743.044.585.505.707.208.70

10.2011.7013.2014.7015.0015.1516.6518.1519.5019.5019.6321.2422.6324.0424.5034.0034.00

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0.0432.0061.0070.50

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Site 908

The southern opening of the Fram Strait is almost completelyblocked by the Hovgàrd Ridge (Myhre, Thiede, Firth, et al., 1995).Small sediment basins on the Hovgárd Ridge contain sediments doc-umenting the geological history of the structural high after subsid-ence and the opening of Fram Strait. Site 908 is located on top of theHovgárd Ridge in about 1273 m water depth at approximately78°23'N, 1°22'E. Hole 908A (Table 10) penetrated 344.6 m of sedi-ment, reaching upper Oligocene sediments. Hole 908B drilled 83.4 mand terminated in Pliocene sediments.

The biostratigraphic results are based on Hole 908A. Unfortunate-ly, planktonic foraminifers occurred only in the upper 15 m of the se-quence, down to Sample 151-908A-2H-CC. In this interval nearlymonospecific associations of the polar-adopted N. pachyderma sin.

160




151-909 A-1H-1, 15-171H-1, 69-711H-1, 82-841H-2, 26-281H-2, 103-1051H-3, 17-191H-3, 105-1071H-4, 6-81H-4, 18-201H-4, 4 1 ^ 31H-4, 69-711H-4, 116-1181H-5, 5-7 to2H-2, 92-962H-2, 106-108 to2H-4, 37-392H-4, 82-842H-4, 104-1062H-5, 13-152H-5, 95-972H-6, 6-8 to2H-6, 120-122 to2H-7, 62-642H-CC3H-1, 46-48 to3H-4, 88-903H-5, 27-293H-5, 80-823H-5, 103-1083H-6, 4 2 ^ 43H-7, 2-43H-CC4H-1,44-464H-2, 72-734H-3, 26-28 to4H-CC5H-1, 128-1305H-2, 44-46 to6H-1,77-796H-1, 131-1336H-CC7H-CC8H-CC

9H-CC to11H-CC

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0.150.690.821.762.533.174.054.564.684.915.195.666.059.95

10.0612.3712.8213.0413.6314.4515.0616.2017.0017.0017.4622.3823.2723.8024.0924.9226.0226.5026.9428.2229.2636.0037.2837.9446.2746.8155.5065.0074.00

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occurred, suggesting an age assignment to the Quaternary. The as-semblages show highly variable abundances, fluctuating severaltimes from abundant to intervals rare or even barren in planktonicforaminifers. Further, one sample per section down to Sample 151-908-28X-6, 95-100 cm (263.05 mbsf) was analyzed. Because of nosuccess, analysis was halted.

EAST GREENLAND MARGIN

Site 913

Site 913 is located in the Greenland Basin. Two holes were drilledat 3.318 m water depth at 75°29.3'N, 6°56.8'W. This site was select-ed to evaluate the onset and history of the East Greenland Current, tomonitor the development of deep-water formation in the Greenland

Sea, and to document the history of IRD input, as well as to determinethe age and character of sediments overlying basement (Myhre,Thiede, Firth, et al, 1995).

Hole 913A (Table 11) penetrated to 84.40 m. The planktonic for-aminifer assemblages are low in diversity and dominated by the polarN. pachyderma sin. The abundance varies considerably, as docu-mented above, in the other northern sites of this leg. Ice-rafted Inoc-eramw y-prisms are documented down to 65.10 mbsf. Sample 151-913A-12X-CC was barren, and the last core of Hole 913A had no re-covery. We analyzed 38 samples from Hole 913A.

Poor recovery severely hampered the analysis of the Quaternaryand late Neogene sediments of Hole 913B to 375.20 mbsf. Afterwashing down to 423.50 m, all core-catcher samples of this hole wereanalyzed. They contained no planktonic foraminifers. Osterman andSpiegler (this volume) analyzed the agglutinated benthic assemblag-es of Site 913. Out of the 300 samples studied, planktonic foramini-fers were seen in only three samples. Sample 151-913B-24R-4, 10-14 cm, at 466.60 mbsf contained a single broken specimen of a smallAcarinina sp., aff. A. rotundimarginata Subbotina (1953), a speciesthat is typical for the middle Eocene. Silicified Subbotina triangu-laris (White) were found in the Samples 151-913B-44R-3, 58-60cm, and 45R-1, 11-14 cm, at 658.09 mbsf and 664.51 mbsf, respec-tively, reaching stratigraphically from Zone P2 (Paleocene) to ZoneP8a (early Eocene). Nevertheless, lacking Paleocene species in thissequence, an age assignment to early Eocene is supposed.

SUMMARY

Age determinations of the sediments recovered during Leg 151are difficult due to the scarcity of planktonic foraminifers and poorlydiversified assemblages. Temperature is the most important factorcontrolling habitat of planktonic foraminifers in high latitudes.

The summary of the planktonic foraminifer zones and some ages,derived from different FOs or LOs of planktonic foraminifers at Sites908 through 913, is given in Figure 2.

In the Quaternary sediments, the polar Neogloboquadrina pachy-derma sin. is the dominant species and shows highly variable abun-dances. The alternations seem to be related to the changes betweenglacial and cold (interglacial) conditions. The whole Quaternary maybe characterized as the Neogloboquadrina pachyderma sin. Zone.The LO of Neogloboquadrina atlantica marks the Quaternary/Pliocene boundary. The N. atlantica Superzone spans the wholePliocene and reaches into the late Miocene. A further subdivision ofthis interval by coiling changes of N. atlantica is impossible. Warmto subtropical intervals in the upper Neogloboquadrina atlantica sin.Zone can be correlated with the planktonic foraminifer Zone N21.Therefore, the late Pliocene may be characterized as cold or cold-temperate with episodic ingressions of warm to subpolar surface wa-ter. The co-occurrence of Neogloboquadrina asanoi marks the influ-ence of Pacific surface water in the late Pliocene.

Rare and spot occurrences of planktonic foraminifers in the Mi-ocene and Paleogene sediments prevent a zonation. The oldest sedi-ments recovered at the East Greenland Margin are of early Eoceneage.

ACKNOWLEDGMENTS

I feel privileged to be reviewed by such outstanding professionalsas P.P.E. Weaver, W.A. Berggren, and W.F. Ruddiman. I greatly ap-preciate the topotype material of TV. asanoi, given by T. Sato. I am in-debted to F. Rack, who made available samples of Hole 910D. To thetechnicians A. Maas, T.M. Kusche, A. von Doetinchem, and J. Hein-ze (all Kiel) I owe special gratitude. Financial support by the Deut-sche Forschungsgemeinschaft (Grant Th 200/17) is acknowledged.

161


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! J K c 2 0 - 2 4 1 0 2 S 2 2 g R |15R-1, 19-24 220.29 B •S15R-2,2-6 221.62 G R R R15R-3,76-80 223.86 G R R "β15R-3, 141-143 224.51 G C -315R-4,4-8 224.64 G C R R S15R-CC 229.60 G R R s g16R-1, 19-24 229.79 G R R ^ o16R-2,26-32 231.36 G C R 1 216R-3, 19-24 232.79 G R R §" ö16R-4, 19-24 234.29 G C R •§ g16R-5, 19-24 235.79 B R U> §

16R-CC 239.20 M R §17R-1, 17-23 to 239.37 5 B *17R-6, 17-23 246.87 P R zmβmmm17R-CC 248.80 B18R-CC 258.50 G R19R-CC 268.10 / No recovery20R-CC 277.80 M R R21R-CC 287.50 No recovery22R-1,20-24 to 287.70 5 B22R-6,20-24 295.20 G R R22R-CC 297.10 G C23R-1,25-28 297.35 B R «23R-2,20-23 298.80 P R23R-3,20-23 300.30 P R23R-4, 20-23 301.80 B23R-CC 306.80 G R R "'"'"" """""

25R-1.20-24 to 316.60 21 B R28R-4,20-24 350.00 G R R28R-CCto 354.90 8 R .§31R-3,23-28 377.33 G R R 131R-3. 26-31 to 377.36 4 B | ~ö u32R-1,28-32 383.88 M R ,2 S §32R-2,28-32 385.38 B < o 232R-3,28-32 386.88 G R E S32R-4,28-32 388.38 P R

932R-5,28-32 to 389.88 17 B

44R-1,32-35 499.32 G R64R-2,92-96 694.42 G R R u67R-4,89-93 697.39 G R g67R-4,92-96 697.42 G R o67R-5,94-98 698.94 G R %67R-6,91-95 729.21 G R j -69R-3,93-96 743.93 G R |70R-5,89-93 756.49 G R 3

76R-1,96-98 808.56 G R

77R-2,94-97 819.74 G R


Table 9 (continued).


81R-2, 95-9985R-1,96-9885R-2, 20-2288R-CC89R-1,97-10089R-2, 97-100103R-1,3-7103R-1,95-99103R-2, 3-7103R-2, 92-96

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Depth(mbsf)

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3H-1, 37-42 to28X-6, 95-100

Depth(mbsf)

0.050.210.430.470.701.345.145.345.406.096.118.789.75

13.4413.57

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REFERENCES

Berggren, W.A., 1972. Cenozoic biostratigraphy and paleobiogeography ofthe North Atlantic. In Laughton, A.S., Berggren, W.A., et al., Init. Repts.DSDP, 12: Washington (U.S. Govt. Printing Office), 965-1002.

Blow, W.H., 1969. Late middle Eocene to Recent planktonic foraminiferalbiostratigraphy. In Brönnimann, P., and Renz, H.H. (Eds.), Proc. FirstInt. Conf. Planktonic Microfossils, Geneva, 1967: Leiden (EJ. Brill),1:199-422.

— , 1979. The Cainozoic Globigerinida: Leiden (E.J. Brill).Bolli, H.M., and Saunders, J.B., 1985. Oligocene to Holocene low latitude

planktonic foraminifera. In Bolli, H.M., Saunders, J.B., and Perch-Nielsen, K. (Eds.), Plankton Stratigraphy: Cambridge (Cambridge Univ.Press), 155-262.

Kennett, J.P., and Srinivasan, M.S., 1980. Surface ultrastructural variation inNeogloboquadrina pachyderma (Ehrenberg): phenotypic variation andphylogeny in the late Cenozoic. Spec. Publ.—Cushman Found. Foramin-iferal Res., 19:134-162.

, 1983. Neogene Planktonic Foraminifera: A Phylogenetic Atlas:Stroudsburg, PA (Hutchinson Ross).

Myhre, A.M., Thiede, J., Firth, J.V., et al., 1995. Proc. ODP, Init. Repts.,151: College Station, TX (Ocean Drilling Program).

Paul, C.R., 1992. Milankovitch cycles and microfossils: principles and prac-tice of palaeoecological analysis illustrated by Cenomanian chalk-marlrhythms. J. Micropaleontol., 11:95-105.

Poore, R.Z., 1979. Oligocene through Quaternary planktonic foraminiferalbiostratigraphy of the North Atlantic: DSDP Leg 49. In Luyendyk, B.P.,Cann, J.R., et al., Init. Repts. DSDP, 49: Washington (U.S. Govt. PrintingOffice), 447-517.

Poore, R.Z., and Berggren, W.A., 1975. Late Cenozoic planktonic foramin-ifera biostratigraphy and paleoclimatology of Hatton-Rockall Basin:DSDP Site 116. J. Foraminiferal Res., 5:270-293.

Spiegler, D., and Jansen, E., 1989. Planktonic foraminifer biostratigraphy ofNorwegian Sea sediments: ODP Leg 104. In Eldholm, O., Thiede, J.,Taylor, E., et al., Proc. ODP, Sci. Results, 104: College Station, TX(Ocean Drilling Program), 681-696.

Subbotina, N.N., 1953. Iskopaemye foraminifery SSSR: Globigerinidae,Hantkeninidae, i Globorotaliidae. Tr. Vses. Nauchno-Issled. Geologo-razved. Nefi. Inst. (VNIGRI), 76.

Weaver, P.P.E., and Clement, B.M., 1986. Synchroneity of Pliocene plank-tonic foraminiferal datums in the North Atlantic. Marine Micropale-ont., 10:295-307.

Date of initial receipt: 14 July 1995Date of acceptance: 1 December 1995Ms 151SR-104

163


S 2 fe

11 | !β β •~ to u

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Core, section, Depth g ^ ^ ^ • g ^ - g g > • l ü Sinterval (cm) (mbsf) z ^ ^ ü ^ ü ^ ^ 2 Z o n e E P o c h

151-913A-1H-1,10-14 0.10 G A R C R R Cold-temp.1H-1,52-55 0.52 G A R Cold-temp.1H-1,86-90 0.86 G A C C Cold-temp.1H-2, 10-14 1.60 G A R Cold-temp.1H-2,86-90 2.36 G A R C Cold-temp.1H-2,129-133 2.79 G A C R R R A R Cold-temp.1H-3, 10-14 3.10 G A A R C R A R Cold-temp.1H-CC 4.40 G A * Cold g2H-CC 9.30 G A R R Cold-temp. S3H-1.0-2 9.31 M R R Cold .S3H-1, 10-14 9.40 G R Cold «3H-2, 10-12 10.90 1 B g3H-3, 10-14 12.40 G R Cold ^3H-5, 10-14 to 15.40 3 B * t ^ g1

4H-2,11-15 19.21 G R Cold g g4H-3,9-13to 20.69 3 B |4H-CC, 9-13 23.30 G C Cold J a4H-CC 23.60 G C R Cold •« ^5H-1, 10-14 23.70 G C R Cold §5H-2.6-10 25.16 G C R Cold o5H-3,7-ll 25.76 G C R Cold "o5H-CC 26.40 G C Cold g>6H-CCto 36.10 3 B * § £ f ^7X-CC 45.80 G R '" Cold" '"8X-CC 55.50 M R Cold9X-1, 13-15 to 55.63 2 B * Cöl<!10X-l,9-12 65.19 G R R ""CoM"10X-1,25-29 65.35 G C Cold1 OX-1,87-89 65.97 G C R Cold10X-CC 74.70 G R Cold11X-CC 84.40 G C Cold

12X-CC 94.00 B R!qr rpn13X-CC 103.60 / "'fro recovery B a r r e n



Yermak Plateau Fram StraitEast-Greenland

Margin

Epoch I Site911

Site910

Site912

Site909

Site908

Site913

Quat. N.p.

LU

>1.7Ma

>4.7Ma

3 Ma#

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= Barren in PF N.p• s. = Nβogloboquadrina pachydβrma sinistral

# = Subtropical PF = Planktonic foraminifers

* = First ice-rafted Inoceram us-prisms

Figure 2. Summary of planktonic foraminifer zones recovered at Sites 908 through 913.

165

D. SPIEGLER

Plate 1. 1-2. Neogloboquadrina pachyderma (Ehrenberg), sinistral, Sample 151-910A-2H-CC, 20-22 cm, Quaternary. 3. Globigerina bulloides Orbigny, Sam-ple 151-909C-103R-2, 3-7 cm, middle Miocene. 4. Orbulina universa Orbigny, Sample 151-911A-16X-3, 116-120 cm, Quaternary. 5-6. Neogloboquadrinaasanoi (Maiyasaito and Sato), Sample 151-909C-10R-5, 43-47 cm, upper Pliocene. 7-8. Neogloboquadrina atlantica (Berggren) sinistral, 7. Sample 151-910C-20R-CC, upper Pliocene. 8. Sample 151-910C-20R-2, 69-72 cm, upper Pliocene. 9. Globoconella cf. inflata (Orbigny), Sample 151-911A-16X-3, 116—120 cm, Quaternary. 10. Globigerinita glutinata (Egger), Sample 151-909C-32R-1, 28-32 cm, upper Pliocene. 11. Globigerinita glutinata (Egger), forma ambi-tacrena (Loeblich and Tappan), Sample 151-909C-103R-2, 3-7 cm, Miocene. 12-13. Paragloborotalia continuosa (Blow), Sample 151-911A-53X-5, 113-117cm, Miocene. 14-15. Turborotalia quinqueloba (Natland), Sample 151-909C-103R-2, 3-7 cm, Miocene. 16. Globigerina praebulloides Blow, Sample 151-911A-53X-5, 113-117 cm, Miocene. 17. Paragloborotalia nana (Bolli), Sample 151-911A-53X-5, 113-117 cm, Miocene. 18. Neogloboquadrina pachyderma(Ehrenberg), dextral, Sample 151-911A-53X-5, 113-117 cm, Miocene.

166


Plate 2. Subtropical upper Pliocene planktonic foraminifers at Site 910. 1. Sphaewidinellopsis sp. juv., aff. 5. paenedehiscens (Blow), Sample 151-910D-10X-3, 74-76 cm. 2. Globigerinoides obliquus extremus Bolli and Bermudez, Sample 151-910D-16X-2, 74-76 cm. 3-4. Globigerinoides ruber (Orbigny), 3. Sample151-910D-16X-2, 74-76 cm, 4. Sample 151-910D-15X-3, 74-76 cm. 5. Globigerinoides trilobus (Reuss), Sample 151-910D-10X-3, 74-76 cm. 6. Globiger-inella aequilateralis (Brady), Sample 151-910D-13X-2, 74-76 cm. 7. Globigerinella siphonifera (Orbigny), Sample 151-910D-14X-2, 74-76 cm. 8. Neoglobo-quadrina dutertrei (Orbigny), Sample 151-910D-15X-3, 74-76 cm. 9. Dentoglobigerina altispira (Cushman and Jarvis), Sample 151-910D-16X-2, 74-76 cm.10. Menardella limbata (Fornasini), Sample 151-910D-15X-3, 74-76 cm. 11-12. Menardella menardii (Parker, Jones, and Brady), 11. Sample 151-910D-15X-3, 74-76 cm. 12. Sample 151-910D-16X-2, 74-76 cm.

167

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(Sites 908–909), Yermak Plateau

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