Diatoms from the Sirius Formation, Transantarctic Mountains
Diatoms from the Sirius Formation, Transantarctic Mountains DAVID M. HARWOOD Department of Geology and Mineralogy
and
Institute of Polar Studies The Ohio State University Columbus, Ohio 43210
The Sirius Formation contains reworked marine diatom assemblages of upper Eocene, upper Oligocene, upper Miocene, and Pliocene ages. These marine components were deposited during repeated marine invasions of intracratonic basins (Wilkes-Pensacola basins of Webb et al. in press) which parallel the eastern flanks of the Transantarctic Mountains. During the late Pliocene-Pleistocene (after deposition of the youngest marine diatoms) these sediments were stripped from their basins and transported to the summits of the Transantarctic Mountains and deposited within the Sirius Formation (see Webb et al., Antarctic Journal, this issue.) These diatom assemblages will aid in unravelling the Cenozoic marine depositional history on the east antarctic craton and provide an approximate stratigraphy of the sedimentary sequence beneath the east antarctic ice sheet. Figure 1 illustrates the episodes of marine deposition as indicated by diatoms which were obtained from sedimentary clasts in the Sirius Formation. Marine diatoms were identified in 9 of 15 samples examined in this preliminary study. Sample materials are from the Reedy and Beardmore glacier areas and from Mount Feather (figure 1 in Webb et al., Antarctic Journal, this issue). These represent the southernmost reported occurrence of marine diatoms to date. Age assignments of diatom assemblages are based on southern high-latitude zonal schemes of Weaver and Gombos (1981),
Gombos and Ciesielski (1983), Ciesielski (1983), McCollum (1975), and Schrader (1976). When diatom zones were not recognizable, the maximum stratigraphic range of specific taxa from the cited literature was used in figure 1. Foraminifera, radiolaria, silicoflagellates, calcareous nannoplankton, sponge spicules, ostracodes, and palynmorphs are associated with the diatoms. Reedy Glacier Area. Sample 64-70 from Tillite Spur contains abundant diatoms of various ages (figure 2). The youngest diatoms include Cosmiodiscus insignus, Coscinodiscus vulnificus, C. lentiginosus, C. kolbei, C. elliptopora, Nitzschia Kerguelensis, N. angulata, Eucampia ballaustiurn and others. These taxa belong to the Cosmiodiscus insignus Zone through Nitzschia interfrigidaria/ Coscinodiscus vulnificus Zone (3.1 to 2.5 million years.) of Ciesielski (1983). Middle-upper Miocene and upper Oligocene! lower Miocene phases are identified by Denticulopsis dimorpha and Synedra jouseana, respectively. Upper Eocene diatoms include Pyxillia prolungata, Hemiaulus incicus, H. pacificus, Tnceratium unguiculatum, Coscinodiscus superbus, Rocella praenitida, Pseudophxillia dubia, Stephanopyxis hyalomarginata, and others. Many of these taxa are not restricted to the upper Eocene; However, because Stephanopyxis eocenica and Pyxillia johnsonia var. intermedia are restricted, the entire assemblage is assumed to be upper Eocene in age. A sample from Metavolcanic Mountain contains Coscinodiscus vulnificus (mid-Pliocene) and Cestodiscus sp. (upper Eocene through upper Oligocene). Sample 64-60 from the Quartz Hills yielded Coscinodiscus lentiginosus, Thalassiosira oestuppii, Actinocyclus ingens s.1., Charcotia actinochilus (previously reported as restricted to the Pleistocene) and Thalassiosira torokina which suggests an upper Miocene-lower Pliocene age (6.6-4.2 million years) according to Ciesielski (1983). Beardmore Glacier Area. A sample from Plunket Point in the Dominion Range yielded very rare diatoms and diatom fragments. The presence of Thalassiosira oestuppii suggests a Pliocene age for this sample. A rich upper Oligocene-early Miocene diatom flora of the Rocella gelida Zone of Combos and Ciesielski (1983) was recovered in a sample from Mount Sirius. The assemblage in-
Figure 1. Episodes of marine deposition in the Wilkes-Pensacola basins as indicated by diatoms. The middle Miocene to early Pliocene interval ( * ) may represent several isolated episodes which cannot be resolved at this time.
98
ANTARCTIC JOURNAL
I' .A t
p *414
N
• . -• :-r.: AZI
2
'lW"
C 6J
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Figure 2. Diatoms from the Sirius Formation: (1) Charcotia actinochilus, sample 64-70; (2) Coscinodiscus vulnificus, sample from Metavolcanlc Mountain; (3) Pyxillia prolungata, sample 64-70; (4) Hemlaulus polycystinorm, sample 64-70; (5) Eucampia balaustium, sample from Mount Feather; (6) Nitzschia kerguelensis, sample 64-70; (7) Synedra jouseana, sample 64-70; (8) radiolarian, sample from Metavolcanic Mountain; (9) Chiasmolithus bidens (calcareous nannoplankton), sample 64-70; (10) Triceratium unguiculatum, sample 64-70; (11) Distephanus speculum (silicoflagellate), sample 64-70; (12) Hemiau!us pacificus, sample 64-70; (13) Stephanopyxls grunowii, sample 64-70; (14) Act inocyclus ingens s.1., sample from Metavolcanic Mountain; (15) Trinacria excavata, sample 64-70; (16) Cosmiodiscus insignus, sample 64-70; (17) Thalassiosira torokina, sample 64-70; (18) Coscinodiscus lentiginosus, sample 64-70.
cludes Rocella vigilans, Rogelida, Synedra jouseana, Rossiella symmetrica, Coscinodiscus oligocenincus, and others. Mount Feather. A sample from Mount Feather yielded the following Late Neogene diatoms: Hemidiscus Karstenii, Coscinodiscus lentiginosus, C. lentiginosus f. obovatus, Nitzschia kerguelensis, Rouxia antarctica, and others. C. lentiginosus f. obovatus is restricted to the middle Pliocene through lowest Pleistocene in the southern ocean according to Weaver and Combos (1981) and DeFelice (1979). An upper Miocene phase is recognized by the presence of Denticulopsis hustedtii. Discussion. The implications of microfossil-rich sedimentary clasts within the Sirius Formation are enormous. The Cenozoic sedimentary sequence hidden beneath the east antarctic ice sheet is represented in the Sirius Formation as individual sedimentary clasts. Thus, the history of marine invasions and sedimentation on the east antarctic craton can be interpreted. Also, the direct cause-and-effect relationship between ice volume 1983 REVIEW
fluctuations and eustatic changes in the Wilkes-Pensacola basins makes this region unique. Episodes of marine sedimentation (as indicated by the diatoms) represent retreat of the east antarctic ice sheet (uncovering the Wilkes-Pensacola basins) and eustatic rise with transgression into these intracratonic basins. Those periods not represented in the Sirius Formation suggest that either marine regression exposed the basin floors or that ice filled the basins during these times. This study was supported by National Science Foundation grant DPP 80-18749A01, Peter-Noel Webb, principal investigator. References Ciesielski, P. F. 1983. The Neogene diatom stratigraphy of DSDP Leg 71. In W. J . Ludwig, V. Krashninnikov, et al., (Eds.), Initial Reports of the
99
Deep Sea Drilling Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office. DeFelice, D. R. 1979. Morphological comparison of Coscinodiscus lentiginosus Jansich and Coscinodiscus obovatus Castracane. Antarctic Journal of the U.S., 14(5) 127-129. Combos, A. M., Jr., and P. F. Ciesielski. 1983. Late Eocene to early Miocene diatoms from the southwest Atlantic. In W. J. Ludwig, V. Krashninnkov, et al., (Eds.), initial Reports of the Deep Sea Drilling
Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office.
McCollum, D. W. 1975. Diatom Stratigraphy of the Southern Ocean. In D. Hayes, L. A. Frakes et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, Vol. 28. Washington, D.C.: U.S. Government Printing Office. Schrader, H. S. 1976. Cenozoic marine planktonic diatom biostratigraphy of the Southern Pacific Ocean. In M. Talwani, C. Udintseu, et al.
Glacial geology and soils in Beacon Valley NOEL POTTER, JR. Department of Geology Dickinson College Carlisle, Pennsylvania 17013
SCOTT C. WILSON
(Eds.), Initial Reports of the Deep Sea Drilling Project, Vol. 35. Wash-
ington, D.C.: U.S. Government Printing Office. Weaver, F. M., and A.M. Combos, Jr., 1981. Southern high latitude diatom biostratigraphy. In J. E. Warme, R. C. Douglas, E. L. Winterer (Eds.), DSDP: A decade of progress. (Special Publication 32.) Tulsa: Society of Economic Paleontologists and Mineralogists. Webb, P. N., D. M. Harwood, B. C. McKelvey, J. H. Mercer, and L. D. Stott. 1983. Late Neogene and Older Cenozoic Microfossils in high elevation deposits of the Transantarctic Mountains: Evidence for marine sedimentation and ice volume variation on the east antarctic craton. Antarctic Journal of the U.S. 18(5). Webb, P. N., D. M. Harwood, B. C. McKelvey, J. H. Mercer, and L. D.
Stott. In press. Cenozoic marine sedimentation and ice volume variation on the East Antarctic craton. Geology.
Index Map 0
90W
. . . : : 90 /
.. ray/or Glacier •
80
Beacon . . : : ::/: : •8016 Valley. : :2 82400..... iHL: •76/82.31 •:::/ .8227 48225/ 07642
Department of Soil Science University of Wisconsin Madison, Wisconsin 53706
.3 .
12.
•8-• 14 . ......... .
1k'.
During the 1982-1983 field season, we spent 6 weeks examin-
ing the glacial history and soils of Beacon Valley (77°53'S
(.1.......... . .:'::.:•
.
1 ::: . ........ .
/
160°40'E), as part of G. H. Denton's and J. G. Bockheim's project
to investigate the glacial history of the McMurdo Sound region. Our major objectives were: (1) to map glacial features and determine the chronology of glacial events using soils as relative age indicators, (2) to study fluctuations of Taylor Glacier where it has entered lower Beacon Valley, and (3) to study the behavior of alpine glaciers and ice-cored rock glaciers that originate in tributary lateral valleys (Lv) (see figure) and mantle the main valley floor. We excavated, described, and sampled 18 soil pits and collected 57 samples for soil chemical analysis. In addition, we collected 57 samples from shallower excavations for particle size
and mineralogical analysis. Surface boulder weathering counts were performed on a minimum of 100 boulders larger than 25 centimeters near each soil pit and on rock glacier lobes in LV 6 and 7. In lower Beacon Valley, differences were observed in soils developed on deposits left by the various advances of Taylor Glacier. The least-developed soils occur on transverse moraine ridges on the main valley floor (2-4 kilometers from Taylor Glacier) and are presumably the youngest of the Taylor ad-
826......[
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/.
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. .
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82-41
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0 2 4 6 8 k Scale Upland, mostly bedrock El Glacier ice Ice-cored rock glacier
El Valley floor fill
LI1 Talus and lateral valley fill • 82-41 Soil pit location (Right) Sketch map (not a geologic map) showing locations of soil pits in Beacon Valley.
100
7 Lateral valley numbers
ANTARCTIC JOURNAL
and
Institute of Polar Studies The Ohio State University Columbus, Ohio 43210
The Sirius Formation contains reworked marine diatom assemblages of upper Eocene, upper Oligocene, upper Miocene, and Pliocene ages. These marine components were deposited during repeated marine invasions of intracratonic basins (Wilkes-Pensacola basins of Webb et al. in press) which parallel the eastern flanks of the Transantarctic Mountains. During the late Pliocene-Pleistocene (after deposition of the youngest marine diatoms) these sediments were stripped from their basins and transported to the summits of the Transantarctic Mountains and deposited within the Sirius Formation (see Webb et al., Antarctic Journal, this issue.) These diatom assemblages will aid in unravelling the Cenozoic marine depositional history on the east antarctic craton and provide an approximate stratigraphy of the sedimentary sequence beneath the east antarctic ice sheet. Figure 1 illustrates the episodes of marine deposition as indicated by diatoms which were obtained from sedimentary clasts in the Sirius Formation. Marine diatoms were identified in 9 of 15 samples examined in this preliminary study. Sample materials are from the Reedy and Beardmore glacier areas and from Mount Feather (figure 1 in Webb et al., Antarctic Journal, this issue). These represent the southernmost reported occurrence of marine diatoms to date. Age assignments of diatom assemblages are based on southern high-latitude zonal schemes of Weaver and Gombos (1981),
Gombos and Ciesielski (1983), Ciesielski (1983), McCollum (1975), and Schrader (1976). When diatom zones were not recognizable, the maximum stratigraphic range of specific taxa from the cited literature was used in figure 1. Foraminifera, radiolaria, silicoflagellates, calcareous nannoplankton, sponge spicules, ostracodes, and palynmorphs are associated with the diatoms. Reedy Glacier Area. Sample 64-70 from Tillite Spur contains abundant diatoms of various ages (figure 2). The youngest diatoms include Cosmiodiscus insignus, Coscinodiscus vulnificus, C. lentiginosus, C. kolbei, C. elliptopora, Nitzschia Kerguelensis, N. angulata, Eucampia ballaustiurn and others. These taxa belong to the Cosmiodiscus insignus Zone through Nitzschia interfrigidaria/ Coscinodiscus vulnificus Zone (3.1 to 2.5 million years.) of Ciesielski (1983). Middle-upper Miocene and upper Oligocene! lower Miocene phases are identified by Denticulopsis dimorpha and Synedra jouseana, respectively. Upper Eocene diatoms include Pyxillia prolungata, Hemiaulus incicus, H. pacificus, Tnceratium unguiculatum, Coscinodiscus superbus, Rocella praenitida, Pseudophxillia dubia, Stephanopyxis hyalomarginata, and others. Many of these taxa are not restricted to the upper Eocene; However, because Stephanopyxis eocenica and Pyxillia johnsonia var. intermedia are restricted, the entire assemblage is assumed to be upper Eocene in age. A sample from Metavolcanic Mountain contains Coscinodiscus vulnificus (mid-Pliocene) and Cestodiscus sp. (upper Eocene through upper Oligocene). Sample 64-60 from the Quartz Hills yielded Coscinodiscus lentiginosus, Thalassiosira oestuppii, Actinocyclus ingens s.1., Charcotia actinochilus (previously reported as restricted to the Pleistocene) and Thalassiosira torokina which suggests an upper Miocene-lower Pliocene age (6.6-4.2 million years) according to Ciesielski (1983). Beardmore Glacier Area. A sample from Plunket Point in the Dominion Range yielded very rare diatoms and diatom fragments. The presence of Thalassiosira oestuppii suggests a Pliocene age for this sample. A rich upper Oligocene-early Miocene diatom flora of the Rocella gelida Zone of Combos and Ciesielski (1983) was recovered in a sample from Mount Sirius. The assemblage in-
Figure 1. Episodes of marine deposition in the Wilkes-Pensacola basins as indicated by diatoms. The middle Miocene to early Pliocene interval ( * ) may represent several isolated episodes which cannot be resolved at this time.
98
ANTARCTIC JOURNAL
I' .A t
p *414
N
• . -• :-r.: AZI
2
'lW"
C 6J
3 10
NON
Figure 2. Diatoms from the Sirius Formation: (1) Charcotia actinochilus, sample 64-70; (2) Coscinodiscus vulnificus, sample from Metavolcanlc Mountain; (3) Pyxillia prolungata, sample 64-70; (4) Hemlaulus polycystinorm, sample 64-70; (5) Eucampia balaustium, sample from Mount Feather; (6) Nitzschia kerguelensis, sample 64-70; (7) Synedra jouseana, sample 64-70; (8) radiolarian, sample from Metavolcanic Mountain; (9) Chiasmolithus bidens (calcareous nannoplankton), sample 64-70; (10) Triceratium unguiculatum, sample 64-70; (11) Distephanus speculum (silicoflagellate), sample 64-70; (12) Hemiau!us pacificus, sample 64-70; (13) Stephanopyxls grunowii, sample 64-70; (14) Act inocyclus ingens s.1., sample from Metavolcanic Mountain; (15) Trinacria excavata, sample 64-70; (16) Cosmiodiscus insignus, sample 64-70; (17) Thalassiosira torokina, sample 64-70; (18) Coscinodiscus lentiginosus, sample 64-70.
cludes Rocella vigilans, Rogelida, Synedra jouseana, Rossiella symmetrica, Coscinodiscus oligocenincus, and others. Mount Feather. A sample from Mount Feather yielded the following Late Neogene diatoms: Hemidiscus Karstenii, Coscinodiscus lentiginosus, C. lentiginosus f. obovatus, Nitzschia kerguelensis, Rouxia antarctica, and others. C. lentiginosus f. obovatus is restricted to the middle Pliocene through lowest Pleistocene in the southern ocean according to Weaver and Combos (1981) and DeFelice (1979). An upper Miocene phase is recognized by the presence of Denticulopsis hustedtii. Discussion. The implications of microfossil-rich sedimentary clasts within the Sirius Formation are enormous. The Cenozoic sedimentary sequence hidden beneath the east antarctic ice sheet is represented in the Sirius Formation as individual sedimentary clasts. Thus, the history of marine invasions and sedimentation on the east antarctic craton can be interpreted. Also, the direct cause-and-effect relationship between ice volume 1983 REVIEW
fluctuations and eustatic changes in the Wilkes-Pensacola basins makes this region unique. Episodes of marine sedimentation (as indicated by the diatoms) represent retreat of the east antarctic ice sheet (uncovering the Wilkes-Pensacola basins) and eustatic rise with transgression into these intracratonic basins. Those periods not represented in the Sirius Formation suggest that either marine regression exposed the basin floors or that ice filled the basins during these times. This study was supported by National Science Foundation grant DPP 80-18749A01, Peter-Noel Webb, principal investigator. References Ciesielski, P. F. 1983. The Neogene diatom stratigraphy of DSDP Leg 71. In W. J . Ludwig, V. Krashninnikov, et al., (Eds.), Initial Reports of the
99
Deep Sea Drilling Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office. DeFelice, D. R. 1979. Morphological comparison of Coscinodiscus lentiginosus Jansich and Coscinodiscus obovatus Castracane. Antarctic Journal of the U.S., 14(5) 127-129. Combos, A. M., Jr., and P. F. Ciesielski. 1983. Late Eocene to early Miocene diatoms from the southwest Atlantic. In W. J. Ludwig, V. Krashninnkov, et al., (Eds.), initial Reports of the Deep Sea Drilling
Project, Vol. 71. Washington, D.C.: U.S. Government Printing Office.
McCollum, D. W. 1975. Diatom Stratigraphy of the Southern Ocean. In D. Hayes, L. A. Frakes et al. (Eds.), Initial Reports of the Deep Sea Drilling Project, Vol. 28. Washington, D.C.: U.S. Government Printing Office. Schrader, H. S. 1976. Cenozoic marine planktonic diatom biostratigraphy of the Southern Pacific Ocean. In M. Talwani, C. Udintseu, et al.
Glacial geology and soils in Beacon Valley NOEL POTTER, JR. Department of Geology Dickinson College Carlisle, Pennsylvania 17013
SCOTT C. WILSON
(Eds.), Initial Reports of the Deep Sea Drilling Project, Vol. 35. Wash-
ington, D.C.: U.S. Government Printing Office. Weaver, F. M., and A.M. Combos, Jr., 1981. Southern high latitude diatom biostratigraphy. In J. E. Warme, R. C. Douglas, E. L. Winterer (Eds.), DSDP: A decade of progress. (Special Publication 32.) Tulsa: Society of Economic Paleontologists and Mineralogists. Webb, P. N., D. M. Harwood, B. C. McKelvey, J. H. Mercer, and L. D. Stott. 1983. Late Neogene and Older Cenozoic Microfossils in high elevation deposits of the Transantarctic Mountains: Evidence for marine sedimentation and ice volume variation on the east antarctic craton. Antarctic Journal of the U.S. 18(5). Webb, P. N., D. M. Harwood, B. C. McKelvey, J. H. Mercer, and L. D.
Stott. In press. Cenozoic marine sedimentation and ice volume variation on the East Antarctic craton. Geology.
Index Map 0
90W
. . . : : 90 /
.. ray/or Glacier •
80
Beacon . . : : ::/: : •8016 Valley. : :2 82400..... iHL: •76/82.31 •:::/ .8227 48225/ 07642
Department of Soil Science University of Wisconsin Madison, Wisconsin 53706
.3 .
12.
•8-• 14 . ......... .
1k'.
During the 1982-1983 field season, we spent 6 weeks examin-
ing the glacial history and soils of Beacon Valley (77°53'S
(.1.......... . .:'::.:•
.
1 ::: . ........ .
/
160°40'E), as part of G. H. Denton's and J. G. Bockheim's project
to investigate the glacial history of the McMurdo Sound region. Our major objectives were: (1) to map glacial features and determine the chronology of glacial events using soils as relative age indicators, (2) to study fluctuations of Taylor Glacier where it has entered lower Beacon Valley, and (3) to study the behavior of alpine glaciers and ice-cored rock glaciers that originate in tributary lateral valleys (Lv) (see figure) and mantle the main valley floor. We excavated, described, and sampled 18 soil pits and collected 57 samples for soil chemical analysis. In addition, we collected 57 samples from shallower excavations for particle size
and mineralogical analysis. Surface boulder weathering counts were performed on a minimum of 100 boulders larger than 25 centimeters near each soil pit and on rock glacier lobes in LV 6 and 7. In lower Beacon Valley, differences were observed in soils developed on deposits left by the various advances of Taylor Glacier. The least-developed soils occur on transverse moraine ridges on the main valley floor (2-4 kilometers from Taylor Glacier) and are presumably the youngest of the Taylor ad-
826......[
10
. 8^-5• .9...
/.
%
. .
1,
'k
': \r I'
82-41
1
0 2 4 6 8 k Scale Upland, mostly bedrock El Glacier ice Ice-cored rock glacier
El Valley floor fill
LI1 Talus and lateral valley fill • 82-41 Soil pit location (Right) Sketch map (not a geologic map) showing locations of soil pits in Beacon Valley.
100
7 Lateral valley numbers
ANTARCTIC JOURNAL
