Pleurosigma in plankton from the Scotia Sea
PLEISTOCENE
Distephanus speculum Zone A
First consistent common occurrence of long-spined Distephanus speculum in the absence of Distephanus bol ioiensjs
UPPER PLIOCENE Distephanus
LOWER PLIOCENE
Not defined but the zone includes all floras above the initial consistent common occurrence of longOpined Distephanus speculum morphotypes
Zone
Dictyocha fibula var. pumila Zone
Last consistent common occurrence of Distephanus boliviensis in the presence of a Distephanus speculum group dominated by short-spined morphttypes Last consistent occurrence of lictyocha aspera oar. pygmaea and 0. fibula var. pumila First common occurrence of Eictyocha aspera oar. pygmaea and I. fibula oar. punila First common occurrence of Eictyocha pseudofibula
Iii iiviery. First consistent occurrence of Mesocena diodon/ Last consistent occurrence of Mes ocena circu lus
UPPER MIOCENE
First consistent occurrence of Mesocena circulus/ Last consistent occurrence of Dictyocha mutabilis Dictyocha mutabilis First consistent occurrence of Dictyocha nutabilis
MIDDLE MIOCENE Eistephanus longispinus Zone
Last consistent occurrence of Corbisema triacantha Corbisema triacantha Zone
Naviculopsis naoicula Zone LOWER MIOCENE
Last occurrence of Naviculopsisnavicula and N. regularis First consistent occurrence of
navicula
Naviculopsis regularis Zone Last common occurrence of Naviculopsis robusta Naviculopsis robusta Zone First common occurrence of Naoiculopsis robusta
UPPER OLIGOCENE
LOWER OLIGOCENE
Nnviculopsis biapiculata Zone
Dictyocha defi andrei Zone
Uictyocha frnuelli, Subzone Mesocena api cul ata Sub zo me
Last consistent occurrence of Elctyocha deflandrei
First common occurrence of Uictyocha frenguellii First consistent common occurrence of Oictyocha deflandrei above the last common occurrence of Dictyocha heuacantha
silicofiagellate biostratigraphy, paleoecology, and systematic paleontology, reference should be made to Ciesielski (in press). This research partially was supported by National Science Foundation grant Gv-42650.
Figure 2. Neogene and Oligocene silicofiagellate zone and subzone definitions. Diagonal lines represent barren stratigraphic sequences.
Pleurosigma in plankton from the Scotia Sea
ANDREW M. GOMBOS, JR.
References
Department of Geology Antarctic Research Facility Florida State University Tallahassee, Florida 32306
Burns, D. A. In press. Nannofossil biostratigraphy for antarctic sediments, leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al.), 28. Washington, D.C., U.S. Government Printing Office. Ciesielski. P. F. In press. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al.), 28. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F. In preparation. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates recovered from piston and drill cores off East Antarctica. Tallahassee, Sedimentology Research Laboratory, Department of Geology, Florida State University. Contribution, 41.
During the recent leg 36 of the Deep Sea Drilling Project (DSDP) I took several plankton samples from the Scotia Sea. Examination of the samples revealed representatives of the diatom genus Pleurosigma (fig.) in a living state. The samples in which Pleurosigma were observed were taken from about 15 meters below the water surface at 56°09'S. 38°11 1W. and 56°20'S. 40 0 25'W. The nearest land is South Georgia Island, more than 210 kilometers to the northeast. Pleurosigma generally is, considered to be a nearshore, benthic diatom. It has, however, been reported from deep ocean sediments by several authors. Kolbe (1954) observed it to occur throughout Swedish Deep Sea Expedition core 76, although it occurred comparatively seldom. Bukry and Foster (1973) recorded
272
ANTARCTIC JOURNAL
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
Distephanus speculum Zone A
First consistent common occurrence of long-spined Distephanus speculum in the absence of Distephanus bol ioiensjs
UPPER PLIOCENE Distephanus
LOWER PLIOCENE
Not defined but the zone includes all floras above the initial consistent common occurrence of longOpined Distephanus speculum morphotypes
Zone
Dictyocha fibula var. pumila Zone
Last consistent common occurrence of Distephanus boliviensis in the presence of a Distephanus speculum group dominated by short-spined morphttypes Last consistent occurrence of lictyocha aspera oar. pygmaea and 0. fibula var. pumila First common occurrence of Eictyocha aspera oar. pygmaea and I. fibula oar. punila First common occurrence of Eictyocha pseudofibula
Iii iiviery. First consistent occurrence of Mesocena diodon/ Last consistent occurrence of Mes ocena circu lus
UPPER MIOCENE
First consistent occurrence of Mesocena circulus/ Last consistent occurrence of Dictyocha mutabilis Dictyocha mutabilis First consistent occurrence of Dictyocha nutabilis
MIDDLE MIOCENE Eistephanus longispinus Zone
Last consistent occurrence of Corbisema triacantha Corbisema triacantha Zone
Naviculopsis naoicula Zone LOWER MIOCENE
Last occurrence of Naviculopsisnavicula and N. regularis First consistent occurrence of
navicula
Naviculopsis regularis Zone Last common occurrence of Naviculopsis robusta Naviculopsis robusta Zone First common occurrence of Naoiculopsis robusta
UPPER OLIGOCENE
LOWER OLIGOCENE
Nnviculopsis biapiculata Zone
Dictyocha defi andrei Zone
Uictyocha frnuelli, Subzone Mesocena api cul ata Sub zo me
Last consistent occurrence of Elctyocha deflandrei
First common occurrence of Uictyocha frenguellii First consistent common occurrence of Oictyocha deflandrei above the last common occurrence of Dictyocha heuacantha
silicofiagellate biostratigraphy, paleoecology, and systematic paleontology, reference should be made to Ciesielski (in press). This research partially was supported by National Science Foundation grant Gv-42650.
Figure 2. Neogene and Oligocene silicofiagellate zone and subzone definitions. Diagonal lines represent barren stratigraphic sequences.
Pleurosigma in plankton from the Scotia Sea
ANDREW M. GOMBOS, JR.
References
Department of Geology Antarctic Research Facility Florida State University Tallahassee, Florida 32306
Burns, D. A. In press. Nannofossil biostratigraphy for antarctic sediments, leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al.), 28. Washington, D.C., U.S. Government Printing Office. Ciesielski. P. F. In press. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates from cores recovered during antarctic leg 28, Deep Sea Drilling Project. In: Initial Reports of the Deep Sea Drilling Project (Hayes, D. E., et al.), 28. Washington, D.C., U.S. Government Printing Office. Ciesielski, P. F. In preparation. Biostratigraphy and paleoecology of Neogene and Oligocene silicoflagellates recovered from piston and drill cores off East Antarctica. Tallahassee, Sedimentology Research Laboratory, Department of Geology, Florida State University. Contribution, 41.
During the recent leg 36 of the Deep Sea Drilling Project (DSDP) I took several plankton samples from the Scotia Sea. Examination of the samples revealed representatives of the diatom genus Pleurosigma (fig.) in a living state. The samples in which Pleurosigma were observed were taken from about 15 meters below the water surface at 56°09'S. 38°11 1W. and 56°20'S. 40 0 25'W. The nearest land is South Georgia Island, more than 210 kilometers to the northeast. Pleurosigma generally is, considered to be a nearshore, benthic diatom. It has, however, been reported from deep ocean sediments by several authors. Kolbe (1954) observed it to occur throughout Swedish Deep Sea Expedition core 76, although it occurred comparatively seldom. Bukry and Foster (1973) recorded
272
ANTARCTIC JOURNAL
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
