Neogene diatom biostratigraphy of the southern ocean
the rare and sporadic occurrance of Pleurosigma from upper Miocene to Pleistocene in DSDP cores 157 and 158 in the eastern equatorial Pacific. Gombos (1973) observed this genus consistently, although rarely, from middle Miocene through Pleistocene in the central equatorial Pacific, hundreds of kilometers from land. The consistent recurrence of a benthic diatom in sediment of the deep ocean is puzzling. Several explanations have been put forth to explain this phenomenon. Bukry and Foster (1973) suggest turbid-flow or erosion during glacial periods of lowered sea level to account for shallow-water deposits in the deep ocean. Tychopelagic transport, i.e. the occurrence in the plankton of bottom-living forms that have been broken from the substrate by storms, waves, etc., is another explanation for the deposition of benthic forms in the deep ocean (Cupp, 1943). These mechanisms undoubtedly account for a large percentage of the benthic forms found in the deep ocean, especially those found in close proximity to land. But when benthic, nearshore forms are found in some frequency in a deep ocean such as the central Pacific, far from land, the possibility of yet another mechanism arises. Schrader (personal communication, 1973) suggests the existence of rare but truly planktonic forms of Pleurosigma in the biocoenoses. This theory is supported by the discovery of living Pleurosigma in surface plankton of the Scotia Sea. It should be remembered that the locations of the plankton samples used in this study are within 240 kilometers of South Georgia Island; Pleurosigma observed in these samples may have been derived, therefore, from shallow waters surrounding that island or perhaps from one of the other islands of the North or South Scotia ridges or the South Sandwich Ridge, which delimit the Scotia Sea. As the current systems of the region are not well known and the period of time during which Pleurosigmo can survive in a tychopelagic situation is uncertain, the true nature of this genus in the plankton of the Scotia Sea is debatable. It has been shown, however, that Pleurosigma does exist in a living state, albeit in reduced numbers (less than 1 percent in moz
: Pleurcsigma recovered in plankton samples from the Scotia Sea.
September-October 1974
samples studied), in the plankton of the Scotia Sea. This suggests the existence of true planktonic forms of this genus. Future research hopefully will shed more light on the ecology of Pleurosigma. Support for this paper was provided by National Science Foundation grant Gv-42650. References Bukry, D., and J . H. Foster. 1973. Silicoflagellate and diatom stratigraphy, leg 16, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (van Andel, T. H., et al.), 16. Washington, D.C., U.S. Government Printing Office. Cupp, Easter. 1943. Marine plankton diatoms of the west coast of North America. Bulletin of Scripps Institution of Oceanography, 5: 1-235. Gombos, A. M., Jr. 1973. A study of some central equatorial Pacific Neogene diatoms. Masters thesis (unpublished), University of Illinois, Urbana. Kolbe, R. W. 1954. Diatoms from equatorial Pacific cores. Swedish Deep Sea Expedition, Report, 6(1): 48p.
Neogene diatom biostratigraphy of the southern ocean DAVID W. MCCOLLTJM
Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306 Utilization of several Eltanin cores in conjunction with sediments recovered from leg 28, Deep Sea Drilling Project (DSDP), have allowed for the establishment of a southern ocean biostratigraphy based on Recent through Middle Miocene diatoms. Eltanin core material that has been dated by paleomagnetic methods was utilized for the Brunhes through Lower Gilbert magnetic epochs (table). Information pertaining to the paleomagnetic and other pertinent data can be found in Hays and Opdyke (1967); Bandy et at. (1971); Watkins and Kennett (1972); Ciesielski and Weaver (1973). The ranges shown in the figure reflect the common to abundant occurrences of the species listed, thereby removing most of the minor fluctuations for individual species. The paleomagnetic ages assigned to zonal boundaries therefore are approximate. Differences in particular instances are thought to represent time transgressive biofacies and possibly reworked sediments. Because of this not all species shown as occurring together necessarily will occur together for a specific period of time for a particular sample. Studies that incorporate biofacies problems are in progress at this time but are not refined sufficiently for regional conclusions. 273
I_'tIEik1_I _! _________
MIDDLE MIOCENE 110ENE I C 2 0
0
An
MATU
III I
2/Io,h,o O WIWO 2-0 //2o,,d,s 22,222,,, 0,222,. ///22p2,o Ad,,1xycAs ,,,os 2
Cosoo,od,so,s ko/b,, R0000 22p/2o,do
-
2002202 C00o,600 2fl/2922T5 N//2s2fl2pT222Ifr2g222o
2
,222,2,22/2 02,12/22/0 ho$22d1,,
0,2,222/2 02202,22,22 010-11 -00-0
Coscinodiscus lentiginosus Partial Range Zone: base defined by latest occurrence of Actinocyclus ingens, top defined as recent sediment formed in southern ocean containing C. lent iginosus. Coscinodiscus elliptipora/Actinocyclus ingens Concurrent Range Zone: base defined by earliest occurrence of C. elliptipora, top defined by latest occurrence of A. ingens. Rhizosolenia barboi/ Nitzschia kerguelensis Partial Range Zone: base defined by joint occurrence of R. barboi and N. kerguelensis immediately following latest occurrence of Coscinodiscus kolbei, top defined by latest occurrence of R. barboi. Coscinodiscus kolbei/Rhizosolenja barboi Range Zone: base defined by joint occurrence of R. barboi with C. kolbei immediately following latest occurrence of Cosmiodiscus insign.s, top defined by latest occurrence of C. kolbei. Cosmiodiscus insignis Partial Range Zone: base defined by latest occurrence of N. interfrigidaria, top defined by latest occurrence of C. insignis. Nitzschia interfrigideria Partial Range Zone: base defined by latest occurrence of N. praeinterfrigidaria, top defined by latest occurrence of N. interfrigidaria. Denticula hustedtii Partial Range Zone: base defined by latest occurrence of Denticula lauta, top defined by latest occurrence of D. hustedtii. Denticula hustedtii/ Denticula lauta Partial Range Zone: base defined by latest occurrence of Denticula antarctica, top defined by latest occurrence of D. lauta. Denticula lauta/Denticula antarctica Partial Range Zone: base defined by earliest occurrence of Denticula hustedtii, top defined by latest occurrence of Dent,cula antarctica. Denticula antarctica/Coscinodiscus lewisianus Zone: based defined by earliest occurrence of C. lewisianus, top defined by earliest occurrence of Denticula hustedtii. Denticula antarctica Partial Range Zone: base defined by earliest occurrence of D. antarctica, tap defined by earliest occurrence of Coscinodiscus lewisianus. Denticula nicobarica Partial Range Zone: base defined by earliest occurrence of D. nicobarica, top defined by earliest occurrence of Denticula antarctica.
A portion of the Denticula hustedtii Zone and the remaining zones are not correlated to paleomagnetic data. The material from which these zones were described was obtained from DSDP leg 28. A brief summary of all of the zonal definitions is given here. For zonal correlations and assemblages reference should be made to McCollum (in press). In an effort to increase the usefulness and value of the antarctic core collection, where applicable the top and bottom of each core in the collection is being dated on the basis of diatom zones; Hopefully this will give investigators useful information for designing projects and selecting core material. As major portions of the collection are completed the information will be published as a supplement to the core description volumes already available through the Antarctic Research Facility, Florida State University. This research was supported by National Science Foundation contract C-564. Unpublished paleomagnetic data for core E50- .-28 was furnished by Dr. Norman Watkins, University of Rhode Island.
References Bandy, 0., R. Casey, and R. Wright. 1971. Late Neogene planktonic zonation, magnetic reversals, and radiometric dates, Antarctic to the tropics. Antarctic Research Series, 15: 1-26. Ciesielski, P., and F. Weaver. 1973. Southern ocean Pliocene paleotemperatures based on silicoflagellates from deep sea cores. Antarctic Journal of the U.S., VIII(5) : 295. Hays, J . , and N. Opdyke. 1967. Antarctic radiolaria, magnetic reversals, and climatic change. Science, 158(3804): 1001-1011. McCollum, D. In press. Antarctic Cenozoic diatoms; leg 28. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al), 28. Washington, D.C., U.S. Government Printing Office. Watkins, N., and J . Kennett. 1972. Regional sedimntary disconformities and Upper Cenozoic changes in bottom water velocities between Australasia and Antarctica, Antarctic Research Series, 19: 273-293.
Eltanin cores used for paleomagnetic data. Core number
El 3-17 E14-7 E14-8 E32-17 E34-18 E36-8 E38-7 E38-8 E50-28 274
Location
65°41.O'S. 58°03.I'S. 59°40.O'S. 60°11.7'S. 60°00.O'S. 58°05.5'S. 61°49.3'S. 61 048.6'S. 62°54.2'S.
124006.3'W. 160009.0'W. 160017.4'W. 144040.0'E. 134052.2'E. 139054.6'E. 149053.0'E. 149054.2'E. 150041.2'E.
Description Recent ............................................ Gilber; "C" Recent ........................................Gilbert ........... Recent........................................... . Gilbert "B" Mid-Matuyama ...................................Gilbert "A" . Lower Gauss ....................................... ..Gilbert "A" Lower Gauss.....................................Upper Glbert Lower Matuyama ................................. Lower Gibert Upper Gilbert..................................... ...Gilbert "A" Mid Gauss ....................................Gilbert "A"
ANTARCTIC JOURNAL
: Pleurcsigma recovered in plankton samples from the Scotia Sea.
September-October 1974
samples studied), in the plankton of the Scotia Sea. This suggests the existence of true planktonic forms of this genus. Future research hopefully will shed more light on the ecology of Pleurosigma. Support for this paper was provided by National Science Foundation grant Gv-42650. References Bukry, D., and J . H. Foster. 1973. Silicoflagellate and diatom stratigraphy, leg 16, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (van Andel, T. H., et al.), 16. Washington, D.C., U.S. Government Printing Office. Cupp, Easter. 1943. Marine plankton diatoms of the west coast of North America. Bulletin of Scripps Institution of Oceanography, 5: 1-235. Gombos, A. M., Jr. 1973. A study of some central equatorial Pacific Neogene diatoms. Masters thesis (unpublished), University of Illinois, Urbana. Kolbe, R. W. 1954. Diatoms from equatorial Pacific cores. Swedish Deep Sea Expedition, Report, 6(1): 48p.
Neogene diatom biostratigraphy of the southern ocean DAVID W. MCCOLLTJM
Antarctic Research Facility Department of Geology Florida State University Tallahassee, Florida 32306 Utilization of several Eltanin cores in conjunction with sediments recovered from leg 28, Deep Sea Drilling Project (DSDP), have allowed for the establishment of a southern ocean biostratigraphy based on Recent through Middle Miocene diatoms. Eltanin core material that has been dated by paleomagnetic methods was utilized for the Brunhes through Lower Gilbert magnetic epochs (table). Information pertaining to the paleomagnetic and other pertinent data can be found in Hays and Opdyke (1967); Bandy et at. (1971); Watkins and Kennett (1972); Ciesielski and Weaver (1973). The ranges shown in the figure reflect the common to abundant occurrences of the species listed, thereby removing most of the minor fluctuations for individual species. The paleomagnetic ages assigned to zonal boundaries therefore are approximate. Differences in particular instances are thought to represent time transgressive biofacies and possibly reworked sediments. Because of this not all species shown as occurring together necessarily will occur together for a specific period of time for a particular sample. Studies that incorporate biofacies problems are in progress at this time but are not refined sufficiently for regional conclusions. 273
I_'tIEik1_I _! _________
MIDDLE MIOCENE 110ENE I C 2 0
0
An
MATU
III I
2/Io,h,o O WIWO 2-0 //2o,,d,s 22,222,,, 0,222,. ///22p2,o Ad,,1xycAs ,,,os 2
Cosoo,od,so,s ko/b,, R0000 22p/2o,do
-
2002202 C00o,600 2fl/2922T5 N//2s2fl2pT222Ifr2g222o
2
,222,2,22/2 02,12/22/0 ho$22d1,,
0,2,222/2 02202,22,22 010-11 -00-0
Coscinodiscus lentiginosus Partial Range Zone: base defined by latest occurrence of Actinocyclus ingens, top defined as recent sediment formed in southern ocean containing C. lent iginosus. Coscinodiscus elliptipora/Actinocyclus ingens Concurrent Range Zone: base defined by earliest occurrence of C. elliptipora, top defined by latest occurrence of A. ingens. Rhizosolenia barboi/ Nitzschia kerguelensis Partial Range Zone: base defined by joint occurrence of R. barboi and N. kerguelensis immediately following latest occurrence of Coscinodiscus kolbei, top defined by latest occurrence of R. barboi. Coscinodiscus kolbei/Rhizosolenja barboi Range Zone: base defined by joint occurrence of R. barboi with C. kolbei immediately following latest occurrence of Cosmiodiscus insign.s, top defined by latest occurrence of C. kolbei. Cosmiodiscus insignis Partial Range Zone: base defined by latest occurrence of N. interfrigidaria, top defined by latest occurrence of C. insignis. Nitzschia interfrigideria Partial Range Zone: base defined by latest occurrence of N. praeinterfrigidaria, top defined by latest occurrence of N. interfrigidaria. Denticula hustedtii Partial Range Zone: base defined by latest occurrence of Denticula lauta, top defined by latest occurrence of D. hustedtii. Denticula hustedtii/ Denticula lauta Partial Range Zone: base defined by latest occurrence of Denticula antarctica, top defined by latest occurrence of D. lauta. Denticula lauta/Denticula antarctica Partial Range Zone: base defined by earliest occurrence of Denticula hustedtii, top defined by latest occurrence of Dent,cula antarctica. Denticula antarctica/Coscinodiscus lewisianus Zone: based defined by earliest occurrence of C. lewisianus, top defined by earliest occurrence of Denticula hustedtii. Denticula antarctica Partial Range Zone: base defined by earliest occurrence of D. antarctica, tap defined by earliest occurrence of Coscinodiscus lewisianus. Denticula nicobarica Partial Range Zone: base defined by earliest occurrence of D. nicobarica, top defined by earliest occurrence of Denticula antarctica.
A portion of the Denticula hustedtii Zone and the remaining zones are not correlated to paleomagnetic data. The material from which these zones were described was obtained from DSDP leg 28. A brief summary of all of the zonal definitions is given here. For zonal correlations and assemblages reference should be made to McCollum (in press). In an effort to increase the usefulness and value of the antarctic core collection, where applicable the top and bottom of each core in the collection is being dated on the basis of diatom zones; Hopefully this will give investigators useful information for designing projects and selecting core material. As major portions of the collection are completed the information will be published as a supplement to the core description volumes already available through the Antarctic Research Facility, Florida State University. This research was supported by National Science Foundation contract C-564. Unpublished paleomagnetic data for core E50- .-28 was furnished by Dr. Norman Watkins, University of Rhode Island.
References Bandy, 0., R. Casey, and R. Wright. 1971. Late Neogene planktonic zonation, magnetic reversals, and radiometric dates, Antarctic to the tropics. Antarctic Research Series, 15: 1-26. Ciesielski, P., and F. Weaver. 1973. Southern ocean Pliocene paleotemperatures based on silicoflagellates from deep sea cores. Antarctic Journal of the U.S., VIII(5) : 295. Hays, J . , and N. Opdyke. 1967. Antarctic radiolaria, magnetic reversals, and climatic change. Science, 158(3804): 1001-1011. McCollum, D. In press. Antarctic Cenozoic diatoms; leg 28. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al), 28. Washington, D.C., U.S. Government Printing Office. Watkins, N., and J . Kennett. 1972. Regional sedimntary disconformities and Upper Cenozoic changes in bottom water velocities between Australasia and Antarctica, Antarctic Research Series, 19: 273-293.
Eltanin cores used for paleomagnetic data. Core number
El 3-17 E14-7 E14-8 E32-17 E34-18 E36-8 E38-7 E38-8 E50-28 274
Location
65°41.O'S. 58°03.I'S. 59°40.O'S. 60°11.7'S. 60°00.O'S. 58°05.5'S. 61°49.3'S. 61 048.6'S. 62°54.2'S.
124006.3'W. 160009.0'W. 160017.4'W. 144040.0'E. 134052.2'E. 139054.6'E. 149053.0'E. 149054.2'E. 150041.2'E.
Description Recent ............................................ Gilber; "C" Recent ........................................Gilbert ........... Recent........................................... . Gilbert "B" Mid-Matuyama ...................................Gilbert "A" . Lower Gauss ....................................... ..Gilbert "A" Lower Gauss.....................................Upper Glbert Lower Matuyama ................................. Lower Gibert Upper Gilbert..................................... ...Gilbert "A" Mid Gauss ....................................Gilbert "A"
ANTARCTIC JOURNAL
