Multiple phases of early Paleozoic deformation in the central ...
interest to see if this new community maintains the strong correspondence evident for the lower Fremouw, or if Antarctica developed a unique fauna during the later portion of the Early Triassic. A paleoecological analysis of the lower Fremouw Formation is advancing concurrent with the description of this new fauna. Extensive collection of the lower Fremouw over four field seaSons has led to a data base that may allow us to determine preferred paleoenvironments for certain taxa. New specimens collected from the Coalsack Bluff and Graphite Peak localities during the 1985-1986 field season are under study, and a complete analysis of the collection made during the 1977- 1978 field season (Cosgriff et al. 1978) has recently been completed. This research is supported by National Science Foundation grants DPP 85-11334 and DPP 84-18354.
References Colbert, E. H. 1982. Triassic vertebrates in the Transantarctic Mountains. In M. Turner and J. Splettstoesser (Eds.), Geology of the Central Transantarctic Mountains. Antarctic Research Series, 39(2), 11-35. Cosgriff, J.W., W.R. Hammer, J.M. Zawiskie, and N.R. Kemp. 1978. New Triassic vertebrates from the Fremouw Formation of the Queen Maud Mountains. Antarctic Journal of the U.S., 13(4), 23-24. Hammer, W. R., and j.W. Cosgriff. 1981. Myosaurus gracilis, an anomodont reptile from the Lower Triassic of Antarctica and South Africa. Journal of Paleontology, 55(2), 410-424. Hammer, W.R., W.J. Ryan, J.W. Tamplin, and S.L. DeFauw. 1986. New vertebrates from the Fremouw Formation (Triassic), Beardmore Glacier region, Antarctica. Antarctic Journal of the U.S., 21(5), 24-26. 86Keyser, A. W., and R.M.H. Smith. 1978. Vertebrate biozonation of the Beaufort Group with special reference to the western Karoo Basin. Annals of the Geological Survey (South Africa), 12, 1-36.
Multiple phases of early Paleozoic deformation in the central Transantarctic Mountains MARGARET
N. REES
Department of Geoscience University of Nevada Las Vegas, Nevada 89154 GARY H. GIRTY
Department of Geological Sciences San Diego State University San Diego, California 92192 SUSAN K. PANTTAJA
Department of Geoscience University of Nevada Las Vegas, Nevada 89154 PETER BRADDOCK
Queen Charlotte College Picton, New Zealand
New structural data from the lower Paleozoic Douglas Conglomerate in the northern Churchill Mountains (figure 1) indicate that the conglomerate was deformed at least three times before the deposition of the overlying Devonian beds of the Beacon Supergroup. Recognition of these post-Lower Cambrian and pre-Devonian events makes all existing tectonic models for the area too simplistic. Our geological investigation of the northern Churchill Moun tains revealed extensive outcrops of Douglas Conglomerate that were not observed or visited by previous field teams (Burgess and Lammerink 1979; Skinner 1964, 1965; Stump et al. 1979); consequently we produced a new geological map and propose new structural interpretations. In addition, south of the mapped area at location 14 (figure 2) trilobites were collected from the Shackleton Limestone and, at location 17, a previously unrecorded, 1000-meter-long exposure of pillow lava was examined and sampled. 1987 REVIEW
Figure 1. Location map showing position of area mapped within the central Transantarctic Mountains and the extent of the Churchill Mountains between the Byrd and Nimrod glaciers. ("MH" denotes Mount Hamilton, "CC" denotes "Crackling Cwm," and "MD" denotes Mount Dick.)
The field team (Rees, Girty, Panttaja, and Braddock) was put into the field by an LC-130 ski-equipped Hercules airplane on 24 November 1986 and picked up from the same location on 5 January 1987. The landing site was located on the Nicholson Peninsula (80°42'S 159°23'E). Overland travel by snowmobile to 33
158'30'
800
C
2 CC - -
0 1 2 3 I_ I I
KILOMETERS SHACKLETON & DOUGLAS XD2 SYNFORM INTERLEAVED DOUGLAS CONGLOMERATE ' Dl REVERSE FAULT E.:...J5HACKLETON LIMESTONE 3 LOCATION NUMBER Figure 2. Generalized geologic map illustrating distribution of Shackleton Limestone and Douglas Conglomerate outcrops mapped during the 1986-1987 field season in the northernmost Churchill Mountains. Note two Major D contractional faults that have been folded by a 0 2 synform. Outcrops at "Crackling Cwm" (CC) are tectonically interleaved Shackleton and Douglas formations and all faults are not shown. Numbers indicate areas where detail structural data was collected. ("MH" denotes Mount Hamilton.)
the Mount Hamilton area (figure 3) was significantly hampered by a broad sastrugi field and numerous white-out days. Throughout the field season, we commonly experienced annoying, low to moderate velocity, katabatic winds. Our primary objective for this project was to collect from the Douglas Conglomerate sufficient field data and laboratory data so that we may determine the age, tectonic setting, provenance, and deformational history of the formation. A synthesis of field data and limited laborarory analyses have already enhanced
MD
17
our understanding of the Early Paleozoic history of the region (Rees and Rowell 1987; Rees and Rowe!l in press.) Structural data were recorded from the Douglas Conglomerate at ten locations (figure 2). At most locations, abundant small-scale, tight to isoclinal folds are deformed by northeast, or northeast and northwest striking asymmetric folds, or their associated axial plane cleavage. These two sets of structures are in turn locally transected by a set of northeast-striking kink bands. This often repeated pattern suggests a hierarchy of structure-forming events that are designated D 1 , D2, and D3 in order of relative ages of formation. Major faults shown in figure 2 dip steeply to the northeast or northwest and are interpreted to be contractional or reverse faults developed during D 1 . Similar types of faults also were observed at "Crackling Cwm," but mapping there is still incomplete. Folds and faults attributed to D 1 deformation record northwest-southeast directed contraction. Significantly, the faults shown in figure 2 are folded, along with S, by a large northwest plunging D2 synform. Conjugate D2 sinistral and dextral verging folds and associated cleavages record northeast-southwest shortening. D 3 kink bands were produced locally by a northwest-southeast contraction. The timing of these events is not well constrained nor is the age of the Douglas. Nevertheless, deposition of the conglomerate post-dates folding and uplift of the Lower Cambrian Shackleton Limestone on which it rests with marked angular unconformity in the southern Churchill Mountains (Rees et al. 1985; Rowell et al. in press; Rowell, Rees, and Braddock 1986; Rowell and Rees in press). Furthermore, preliminary potassium/argon dates derived from clasts from the Douglas suggest that their source area was uplifted during the Ross Orogeny. It therefore is possible that all three deformational events recorded in the Douglas Conglomerate occurred after the Ross Orogeny and before the deposition of Devonian sediments. Sedimentological data and samples of the Douglas were collected from ridges and nunataks numbered 1 through 12, excluding outcrop 7 (figure 3). Preliminary detrital mode analyses of sandstone and rudstone units suggest both a recycled orogen (sensu Dickinson and Suczek 1979) and basement uplift (sensu Dickinson et al. 1983) provenance for the Douglas. Clasts are primarily limestone eroded from the Shackleton and several types of sandstone and quartzite probably derived from the Proterozoic basement. Less common are granitoid, rhyolite, basalt, chert, and dolomite clasts whose sources are not yet
MH
14 13
7
6
Figure 3. A perspective sketch of the field area illustrating ridges and nunataks from which field data and samples were collected from the Shackleton Limestone, Douglas Conglomerate, and a pillow lava sequence. ("MD" denotes Mount Dick, and "MH" denotes Mount Hamilton.) 34
ANTARCTIC JOURNAL
known. The framework modes and their sources suggest deposition in a foreland basin but do not preclude accumulation in a pull-apart basin. Resolution of basin type is hindered because sequences are fragmentary, folded, and sheared, thus obscuring stratigraphic relationships and thicknesses. In addition, basin type has not been clarified by lithofacies analysis because the lithofacies imply development of alluvial fans and fan deltas in lacustrine and marine environments (Rees and Rowell in press) and all such associations are common to both basin types. This work was supported in part by National Science Foundation grant DPP 85-18157 to the University of Nevada Las Vegas. References Burgess, C.J., and W. Lammerink. 1979. Geology of the Shackleton Limestone (Cambrian) in the Byrd Glacier area. New Zealand Antarctic Record, 2, 12-16.
Dickinson, W. R., and C. A. Suczek. 1979. Plate tectonics and sandstone compositions. American Association of Pet roleu in Geologists Bulletin, 63, 2164-2182.
Dickinson, W.R., L.S. Beard, G.R. Brakenridge, J.L. Erjavec, R.C. Ferguson, K.F. Inman, R.A. Knepp, F.A. Lindberg, and P.T. Ryberg. 1983. Provenance of North American Phanerozoic sandstones in relation to tectonic setting. Geological Society of America Bulletin, 94, 222-235.
Rees, M.N., and A.J. Rowell. 1987. The pre-Devonian Paleozoic Douglas Conglomerate of the Transantarctic Mountains: Origin and depo-
Paleoenvironmental studies of nonmarine diatoms in Quaternary antarctic sediments REED P. SCHERER
Department of Geology and Mineralogy
and Byrd Polar Research Center Ohio State University Columbus, Ohio 43210-1293
Nonmarine sediments from ice-free areas of southern Victoria Land contain a largely unexploited paleoclimatic resource. Diatom assemblages within lacustrine sediment sequences are being used to evaluate Quaternary paleoenvironments in the McMurdo Sound region. In the first phase of the study, begun during the 1986-1987 field season, lacustrine and associated deltaic sediments were sampled at outcrops in lower Taylor Valley, the Cape Chocolate region, Wright Valley, Brown Peninsula, East Dailey Island, and Ross Island. Results from two sequences near Cape Chocolate and one in lower Taylor Valley are reported here. These samples were processed for diatom analysis using a method (Scherer in preparation) which allows the establishment of absolute abundance (diatoms per gram of dry sediment). This relationship allows comparison of diatom productivity and sediment input. 1987
REVIEW
sitional setting. Fifth International Syinposiu in on Antarctic Earth Sciences Abstracts.
Rees, MN., and A.J. Rowell. In press. The pre-Devonian Paleozoic clastics of the central Transantarctic Mountains: Stratigraphy and depositional settings. Volume of the Fifth International Symposium on Antarctic Earth Sciences. Cambridge, U.K. Rees, MN., A.J. Rowell, B.R. Pratt, and P. Braddock. 1985. The Byrd
Group of the Holyoake Range, central Transantarctic Mountains.
Antarctic Journal of the U.S., 20(5), 3-5.
Rowell, A.J., and M.N. Rees. In press. Setting and significance of the Shackleton Limestone, central Transantarctic Mountains. Volume of the Fifth International Symposium on Antarctic Earth Sciences.
Cambridge, U.K. Rowell, A.J., M.N. Rees, and P. Braddock. 1986. Pre-Devonian Paleozoic rocks of the central Transantarctic Mountains. Antarctic Journal of the U.S., 21(5), 48-50.
Rowell, A.J., M.N. Rees, R.A. Cooper, and B.R. Pratt. In press. Early Paleozoic history of the central Transantarctic Mountains: Evidence from the Holyoake Range, Antarctica. New Zealand Journal of Geology and Geophysics.
Skinner, D.N.B. 1964. A summary of the geology of the region between Byrd and Starshot glaciers, south Victoria Land. In R.J. Adie (Ed.), Antarctic geology. Amsterdam: North Holland. Skinner, D.N.B. 1965. Petrographic criteria of the rock units between the Byrd and Starshot glaciers, south Victoria Land, Antarctica. New Zealand Journal of Geology and Geophysics. 8, 292-303.
Stump, E., M.R. Sheridan, S.G. Borg, P.H. Lowry, and P.V. Colbert. 1979. Geological investigations in the Scott Glacier and Byrd Glacier areas. Antarctic Journal of the U.S., 14(5), 39-40.
Diatoms within these sediments are compared with modern floras in sediment from Lake Vanda in Wright Valley and numerous meltwater streams and ponds distributed throughout Wright Valley, lower Taylor Valley, Cape Chocolate, Ross Island, Brown Peninsula, and on the McMurdo Ice Shelf around East Dailey Island. Modern diatom assemblages within these samples, as well as those reported in the literature, provide an analog for ecologic interpretation of fossil assemblages and their sedimentary environments. Older nonmarine diatom floras from upper Pliocene/Pleistocene sediments from DVDP-15 and CIROS2* drill cores in McMurdo Sound and Ferrar Fjord are also under study. A paleoecologic model is being constructed based in part on these results. Discontinuous outcrops of lacustrine and deltaic sediments are scattered along valley walls and dry basins of southern Victoria Land (Debenham 1921; Speden 1960; Péwé 1960; Kellogg et al. 1980). These generally represent only high stands of previous lake levels, and thus do not contain continuous stratigraphic successions. A high-resolution Late Quaternary paleoclimatic signal, based on diatom, sedimentologic and chemical analyses, may be extracted from the near-continuous sediment records underlying certain modern lakes. The only available record of this kind is the upper 4 meters of DVDP-4A in Lake Vanda. Although badly disturbed by drilling, this succession showed evidence of major changes in sedimentation, including periodic evaporite deposition (Brady 1981). Continuous sedimentary records underlying modern lakes need to be ex-
* "DVDP" denotes Dry Valley Drilling Project and "CIROS" denotes Cenozoic Investigations of the Ross Sea. 35
References Colbert, E. H. 1982. Triassic vertebrates in the Transantarctic Mountains. In M. Turner and J. Splettstoesser (Eds.), Geology of the Central Transantarctic Mountains. Antarctic Research Series, 39(2), 11-35. Cosgriff, J.W., W.R. Hammer, J.M. Zawiskie, and N.R. Kemp. 1978. New Triassic vertebrates from the Fremouw Formation of the Queen Maud Mountains. Antarctic Journal of the U.S., 13(4), 23-24. Hammer, W. R., and j.W. Cosgriff. 1981. Myosaurus gracilis, an anomodont reptile from the Lower Triassic of Antarctica and South Africa. Journal of Paleontology, 55(2), 410-424. Hammer, W.R., W.J. Ryan, J.W. Tamplin, and S.L. DeFauw. 1986. New vertebrates from the Fremouw Formation (Triassic), Beardmore Glacier region, Antarctica. Antarctic Journal of the U.S., 21(5), 24-26. 86Keyser, A. W., and R.M.H. Smith. 1978. Vertebrate biozonation of the Beaufort Group with special reference to the western Karoo Basin. Annals of the Geological Survey (South Africa), 12, 1-36.
Multiple phases of early Paleozoic deformation in the central Transantarctic Mountains MARGARET
N. REES
Department of Geoscience University of Nevada Las Vegas, Nevada 89154 GARY H. GIRTY
Department of Geological Sciences San Diego State University San Diego, California 92192 SUSAN K. PANTTAJA
Department of Geoscience University of Nevada Las Vegas, Nevada 89154 PETER BRADDOCK
Queen Charlotte College Picton, New Zealand
New structural data from the lower Paleozoic Douglas Conglomerate in the northern Churchill Mountains (figure 1) indicate that the conglomerate was deformed at least three times before the deposition of the overlying Devonian beds of the Beacon Supergroup. Recognition of these post-Lower Cambrian and pre-Devonian events makes all existing tectonic models for the area too simplistic. Our geological investigation of the northern Churchill Moun tains revealed extensive outcrops of Douglas Conglomerate that were not observed or visited by previous field teams (Burgess and Lammerink 1979; Skinner 1964, 1965; Stump et al. 1979); consequently we produced a new geological map and propose new structural interpretations. In addition, south of the mapped area at location 14 (figure 2) trilobites were collected from the Shackleton Limestone and, at location 17, a previously unrecorded, 1000-meter-long exposure of pillow lava was examined and sampled. 1987 REVIEW
Figure 1. Location map showing position of area mapped within the central Transantarctic Mountains and the extent of the Churchill Mountains between the Byrd and Nimrod glaciers. ("MH" denotes Mount Hamilton, "CC" denotes "Crackling Cwm," and "MD" denotes Mount Dick.)
The field team (Rees, Girty, Panttaja, and Braddock) was put into the field by an LC-130 ski-equipped Hercules airplane on 24 November 1986 and picked up from the same location on 5 January 1987. The landing site was located on the Nicholson Peninsula (80°42'S 159°23'E). Overland travel by snowmobile to 33
158'30'
800
C
2 CC - -
0 1 2 3 I_ I I
KILOMETERS SHACKLETON & DOUGLAS XD2 SYNFORM INTERLEAVED DOUGLAS CONGLOMERATE ' Dl REVERSE FAULT E.:...J5HACKLETON LIMESTONE 3 LOCATION NUMBER Figure 2. Generalized geologic map illustrating distribution of Shackleton Limestone and Douglas Conglomerate outcrops mapped during the 1986-1987 field season in the northernmost Churchill Mountains. Note two Major D contractional faults that have been folded by a 0 2 synform. Outcrops at "Crackling Cwm" (CC) are tectonically interleaved Shackleton and Douglas formations and all faults are not shown. Numbers indicate areas where detail structural data was collected. ("MH" denotes Mount Hamilton.)
the Mount Hamilton area (figure 3) was significantly hampered by a broad sastrugi field and numerous white-out days. Throughout the field season, we commonly experienced annoying, low to moderate velocity, katabatic winds. Our primary objective for this project was to collect from the Douglas Conglomerate sufficient field data and laboratory data so that we may determine the age, tectonic setting, provenance, and deformational history of the formation. A synthesis of field data and limited laborarory analyses have already enhanced
MD
17
our understanding of the Early Paleozoic history of the region (Rees and Rowell 1987; Rees and Rowe!l in press.) Structural data were recorded from the Douglas Conglomerate at ten locations (figure 2). At most locations, abundant small-scale, tight to isoclinal folds are deformed by northeast, or northeast and northwest striking asymmetric folds, or their associated axial plane cleavage. These two sets of structures are in turn locally transected by a set of northeast-striking kink bands. This often repeated pattern suggests a hierarchy of structure-forming events that are designated D 1 , D2, and D3 in order of relative ages of formation. Major faults shown in figure 2 dip steeply to the northeast or northwest and are interpreted to be contractional or reverse faults developed during D 1 . Similar types of faults also were observed at "Crackling Cwm," but mapping there is still incomplete. Folds and faults attributed to D 1 deformation record northwest-southeast directed contraction. Significantly, the faults shown in figure 2 are folded, along with S, by a large northwest plunging D2 synform. Conjugate D2 sinistral and dextral verging folds and associated cleavages record northeast-southwest shortening. D 3 kink bands were produced locally by a northwest-southeast contraction. The timing of these events is not well constrained nor is the age of the Douglas. Nevertheless, deposition of the conglomerate post-dates folding and uplift of the Lower Cambrian Shackleton Limestone on which it rests with marked angular unconformity in the southern Churchill Mountains (Rees et al. 1985; Rowell et al. in press; Rowell, Rees, and Braddock 1986; Rowell and Rees in press). Furthermore, preliminary potassium/argon dates derived from clasts from the Douglas suggest that their source area was uplifted during the Ross Orogeny. It therefore is possible that all three deformational events recorded in the Douglas Conglomerate occurred after the Ross Orogeny and before the deposition of Devonian sediments. Sedimentological data and samples of the Douglas were collected from ridges and nunataks numbered 1 through 12, excluding outcrop 7 (figure 3). Preliminary detrital mode analyses of sandstone and rudstone units suggest both a recycled orogen (sensu Dickinson and Suczek 1979) and basement uplift (sensu Dickinson et al. 1983) provenance for the Douglas. Clasts are primarily limestone eroded from the Shackleton and several types of sandstone and quartzite probably derived from the Proterozoic basement. Less common are granitoid, rhyolite, basalt, chert, and dolomite clasts whose sources are not yet
MH
14 13
7
6
Figure 3. A perspective sketch of the field area illustrating ridges and nunataks from which field data and samples were collected from the Shackleton Limestone, Douglas Conglomerate, and a pillow lava sequence. ("MD" denotes Mount Dick, and "MH" denotes Mount Hamilton.) 34
ANTARCTIC JOURNAL
known. The framework modes and their sources suggest deposition in a foreland basin but do not preclude accumulation in a pull-apart basin. Resolution of basin type is hindered because sequences are fragmentary, folded, and sheared, thus obscuring stratigraphic relationships and thicknesses. In addition, basin type has not been clarified by lithofacies analysis because the lithofacies imply development of alluvial fans and fan deltas in lacustrine and marine environments (Rees and Rowell in press) and all such associations are common to both basin types. This work was supported in part by National Science Foundation grant DPP 85-18157 to the University of Nevada Las Vegas. References Burgess, C.J., and W. Lammerink. 1979. Geology of the Shackleton Limestone (Cambrian) in the Byrd Glacier area. New Zealand Antarctic Record, 2, 12-16.
Dickinson, W. R., and C. A. Suczek. 1979. Plate tectonics and sandstone compositions. American Association of Pet roleu in Geologists Bulletin, 63, 2164-2182.
Dickinson, W.R., L.S. Beard, G.R. Brakenridge, J.L. Erjavec, R.C. Ferguson, K.F. Inman, R.A. Knepp, F.A. Lindberg, and P.T. Ryberg. 1983. Provenance of North American Phanerozoic sandstones in relation to tectonic setting. Geological Society of America Bulletin, 94, 222-235.
Rees, M.N., and A.J. Rowell. 1987. The pre-Devonian Paleozoic Douglas Conglomerate of the Transantarctic Mountains: Origin and depo-
Paleoenvironmental studies of nonmarine diatoms in Quaternary antarctic sediments REED P. SCHERER
Department of Geology and Mineralogy
and Byrd Polar Research Center Ohio State University Columbus, Ohio 43210-1293
Nonmarine sediments from ice-free areas of southern Victoria Land contain a largely unexploited paleoclimatic resource. Diatom assemblages within lacustrine sediment sequences are being used to evaluate Quaternary paleoenvironments in the McMurdo Sound region. In the first phase of the study, begun during the 1986-1987 field season, lacustrine and associated deltaic sediments were sampled at outcrops in lower Taylor Valley, the Cape Chocolate region, Wright Valley, Brown Peninsula, East Dailey Island, and Ross Island. Results from two sequences near Cape Chocolate and one in lower Taylor Valley are reported here. These samples were processed for diatom analysis using a method (Scherer in preparation) which allows the establishment of absolute abundance (diatoms per gram of dry sediment). This relationship allows comparison of diatom productivity and sediment input. 1987
REVIEW
sitional setting. Fifth International Syinposiu in on Antarctic Earth Sciences Abstracts.
Rees, MN., and A.J. Rowell. In press. The pre-Devonian Paleozoic clastics of the central Transantarctic Mountains: Stratigraphy and depositional settings. Volume of the Fifth International Symposium on Antarctic Earth Sciences. Cambridge, U.K. Rees, MN., A.J. Rowell, B.R. Pratt, and P. Braddock. 1985. The Byrd
Group of the Holyoake Range, central Transantarctic Mountains.
Antarctic Journal of the U.S., 20(5), 3-5.
Rowell, A.J., and M.N. Rees. In press. Setting and significance of the Shackleton Limestone, central Transantarctic Mountains. Volume of the Fifth International Symposium on Antarctic Earth Sciences.
Cambridge, U.K. Rowell, A.J., M.N. Rees, and P. Braddock. 1986. Pre-Devonian Paleozoic rocks of the central Transantarctic Mountains. Antarctic Journal of the U.S., 21(5), 48-50.
Rowell, A.J., M.N. Rees, R.A. Cooper, and B.R. Pratt. In press. Early Paleozoic history of the central Transantarctic Mountains: Evidence from the Holyoake Range, Antarctica. New Zealand Journal of Geology and Geophysics.
Skinner, D.N.B. 1964. A summary of the geology of the region between Byrd and Starshot glaciers, south Victoria Land. In R.J. Adie (Ed.), Antarctic geology. Amsterdam: North Holland. Skinner, D.N.B. 1965. Petrographic criteria of the rock units between the Byrd and Starshot glaciers, south Victoria Land, Antarctica. New Zealand Journal of Geology and Geophysics. 8, 292-303.
Stump, E., M.R. Sheridan, S.G. Borg, P.H. Lowry, and P.V. Colbert. 1979. Geological investigations in the Scott Glacier and Byrd Glacier areas. Antarctic Journal of the U.S., 14(5), 39-40.
Diatoms within these sediments are compared with modern floras in sediment from Lake Vanda in Wright Valley and numerous meltwater streams and ponds distributed throughout Wright Valley, lower Taylor Valley, Cape Chocolate, Ross Island, Brown Peninsula, and on the McMurdo Ice Shelf around East Dailey Island. Modern diatom assemblages within these samples, as well as those reported in the literature, provide an analog for ecologic interpretation of fossil assemblages and their sedimentary environments. Older nonmarine diatom floras from upper Pliocene/Pleistocene sediments from DVDP-15 and CIROS2* drill cores in McMurdo Sound and Ferrar Fjord are also under study. A paleoecologic model is being constructed based in part on these results. Discontinuous outcrops of lacustrine and deltaic sediments are scattered along valley walls and dry basins of southern Victoria Land (Debenham 1921; Speden 1960; Péwé 1960; Kellogg et al. 1980). These generally represent only high stands of previous lake levels, and thus do not contain continuous stratigraphic successions. A high-resolution Late Quaternary paleoclimatic signal, based on diatom, sedimentologic and chemical analyses, may be extracted from the near-continuous sediment records underlying certain modern lakes. The only available record of this kind is the upper 4 meters of DVDP-4A in Lake Vanda. Although badly disturbed by drilling, this succession showed evidence of major changes in sedimentation, including periodic evaporite deposition (Brady 1981). Continuous sedimentary records underlying modern lakes need to be ex-
* "DVDP" denotes Dry Valley Drilling Project and "CIROS" denotes Cenozoic Investigations of the Ross Sea. 35
