Dry valleys/McMurdo Sound magnetostratigraphy and ...
Dry valleys/McMurdo Sound magnetostratigraphy and sedimentology project: A progress report D.P. ELSTON and H.J. RIECK U.S. Geological Survey Flagstaff, Arizona 86001
P.H. ROBINSON New Zealand Geological Survey Lower Hutt, New Zealand
Work continues on this joint U.S./New Zealand multidisciplinary study of glacial deposits of the ice-free valleys in southern Victoria Land and of McMurdo Sound. Current studies in eastern (lower) Taylor Valley are aimed at developing detailed stratigraphic, paleomagnetic, and sedimentologic data from drill-core sections and are supplemented by paleontologic information provided by other workers. We hope to develop a better understanding of the Neogene glacial history of the region, particularly as it pertains to relationships between thickness and incursions of the Ross ice sheet, and potential correlations with changes in sea level and worldwide changes in climate. Our studies have been concentrated principally in eastern Taylor Valley, the only place amenable for the subsurface study of a thick series of interbedded glacial deposits of Ross Sea and continental (Taylor Glacier) origin. To date, 12 Winkie core holes, up to 70 meters in depth and totaling 485 meters of cored section, have been drilled along the length of the valley (figure 1). Drill-hole locations were selected to help answer questions
that arose during the analysis of Dry Valley Drilling Project (DVDP) cores drilled about a decade ago (see Elston and Bressler 1981; Elston, Robinson, and Bressler 1981; Purucker, Elston, and Bressler 1981). High core recovery and unbroken strings of core up to 3 meters in length, allowed us routinely to obtain oriented cores, thus permitting us to determine magnetic declinations as well as inclinations. Drilling has been conducted by the Antarctic Division of the New Zealand Department of Scientific and Industrial Research (DSIR). Sedimentological studies have been the responsibility of P.H. Robinson of the DSIR. Paleomagnetic studies, which include the determination of susceptibility and magnetic fabric as well as remanence, are being carried out by H.J. Rieck at the U.S. Geological Survey's paleomagnetics laboratory at Flagstaff. Detailed core logging and sampling have been a joint effort, conducted at the Thiel Earth Science Laboratory at McMurdo Station. Supporting paleontologic studies are being carried out by D. and T. Kellogg, University of Maine, Orono, and by D. Harwood, Institute of Polar Studies, Ohio State University. Lithostratigraphic and paleomagnetic correlations supported by sedimentologic and paleontologic data are being developed, but correlations are not yet final (see Robinson 1985). Paleomagnetic analysis of holes ETV-11, -12, and -13 is in progress. ("ETV" denotes "eastern Taylor Valley.") Lithologic logs of the cores at 1:200 scale have been published (Robinson and Jaegers 1984). Correlations shown on figure 2 reflect time lines derived from paleomagnetic and paleontologic data. Quality of stratigraphic information in the western part of the valley ranges from poor to good because of a variability in the ice cement encountered in sections drilled near the lakes. A second line of drill holes (open circles, figure 1) is planned for the western part of the valley for the 1986 - 1987 austral summer well away from the lakes. The objective will be to document in detail multiple incursions of the Ross ice sheet suggested from the previous drilling. These incursions may correlate with multiple, but currently undated, moraines and strand lines preserved locally near the western end of lower Taylor Valley. If correlations can be developed, the currently accepted picture of incursions of the Ross ice sheet during the past 500,000 or more years will become considerably more complicated. In
rlgure 1. Map showing locations of drill holes in eastern Taylor Valley, southern Victoria Land. ("km" denotes "kilometer?') 1985 REVIEW
15
LOWER TAYLOR VALLEY EAST
WEST Suess Meters Glacier 150
Lake Hoare
100
DVDP
Canada Glacier
New Harbor Meters ISO
Lake Fryxell ETV Ely ETV 59
ETV
ETV 12
50
ETV 10
ETV 13
low 50 tOO BASEMENT
Normal polarity
';:
Reverse polarity
I km approx. Poleomagnatic analysis in progress ------1 250
t±:
BRUNHESDVD
0
150
100
I ETV
Boundary between high and low McMu(do volcanic content
50 SEA LEVEL 0 SO 100 ISO ..200 250
Figure 2. Cross-section along axis of eastern Taylor Valley showing paleomagnetic polarity, visional correlations, and inferred ages of glacial strata. ("km" denotes "kilometer:')
addition, we will propose that the Longyear drill rig reoccupy the DVDP-11 drill site and complete coring of marine glacial deposits of Miocene and possibly greater age to the basement. Such information would enhance the likelihood of correlations with sections cored in the Ross Sea, and should provide information concerning the onset of accumulation of glacial sediments in the Taylor Valley fjord.
The Photogrammetric Section of the Branch of Astrogeology, U.S. Geological Survey, Flagstaff, has prepared a 1:25,000-scale topographic map of eastern Taylor Valley from recent (1983) aerial photographs. The contour interval of this map is 20 meters, with supplementary 10-meter contours in the valley floor. The master copy of the map is at the Reston, Virginia, offices of the National Mapping Division, U.S. Geological Sur-
Figure 3. Equal area plots of averaged directions of maximum magnetic susceptibility of samples from (A) basal till of Taylor Glacier (site mean declination 60.70, inclination - 8.1 0, alpha 95 19.50), and (B) water-laid glacial material near Lake Bonney (site mean declination 3.8 0, inclination —38.40, alpha 95 77.2 0). Arrows indicate direction of valley axis; X marks mean of direction of maximum magnetic susceptibility. Repeated measurements of invididual samples gave consistent results for A, and erratic results for B, indicating that B has very weak (if any) magnetic fabric. 16
ANTARCTIC JOURNAL
vey. This map will be used as a base for the preparation of a geologic map of glacial deposits in and adjacent to lower Taylor Valley. Five core holes, ETV-9 to -13 (figure 1), were drilled during the 1983 - 1984 austral summer. They ranged in depth from 16.9 meters to 70.9 meters. Holes ETV-10, -12, and -13 in more westerly parts of the valley penetrated terrestrial deposits of inferred Taylor Glacier (east antarctic) origin. Core near the bottom of hole ETV-10, from a depth of 67 to 70 meters, contains an assemblage of abundant barnacle and bivalve fragments, locally constituting as much as 30 percent of the core. This assemblage, which exhibits a low diversity, is dominated by the barnacle Bathylasma corolliforme (Hoek) and the bivalve Hiatella sp. (Buckeridge and Dell personal communications). However, only a few fragments of microfossils have been found in these beds (Harwood personal communication 1985). The barnacle, known in antarctic waters from strata of early Pleistocene to Recent age, provides a tentative maximum age for the fossiliferous beds in hole ETV-10 (Newman and Ross 1971). This, coupled with a preliminary polarity zonation for hole ETV-10 (figure 2), suggests a late Pliocene or early Pleistocene age for the strata, possibly correlative with the Olduvai normal polarity interval. Core from the CIROS-2 hole, drilled about 1 kilometer east of the terminus of Ferrar Glacier by the New Zealand DSIR in October and November 1984, has been sampled at Wellington by H. Rieck. The samples are currently being analyzed at the Flagstaff paleomagnetics laboratory. The objective is to provide polarity information to supplement paleontologic data for temporal evaluation. This work complements a recent reevaluation of the polarity zonation for McMurdo Sound Sediment and Tectonic Studies hole MSSTS-1 (Elston and Bressler in press) drilled in 1979. The polarity zonation from a depth of 116 meters to 226 meters in MSSTS-1 has been assigned to the late Oligocene on the basis of diatoms (Harwood personal communication 1984, 1985; Harwood in press), and the zonation has allowed the accumulation rate to be estimated for the interval 31 to 25 million years. Cores from the ETV drill holes in Taylor Valley are being analyzed by H. Rieck for magnetic fabric (anisotropy of magnetic susceptibility) with the objective of discriminating water-laid diamictons from ice-deposited glacial till. Magnetic fabric observed in the drill core is being evaluated with respect to control data obtained from oriented samples of basal till having known sedimentologic fabric (Robinson 1979) collected from near Taylor Glacier, and from water-laid deposits of Lake Bonney collected in upper Taylor Valley. The tills display a fabric having a shallow inclination that is aligned with the long axis of the valley, whereas the water-laid deposits characteristically display no anisotropy of susceptibility (figure 3).
185
REVIEW
This report is based upon work supported by National Science Foundation grant DPP 81-20877, and by the U.S. Geological Survey. The Antarctic Division, New Zealand Department of Scientific and Industrial Research, furnished the Winkie drill rig and drillers John Hay, Stephen Pilcher, Bruce Morris, and Warwick Potter, whose efforts are greatly appreciated. Gary Calderone, U.S. Geological Survey, ably assisted at the drill site and in the logging and sampling of cores.
References
Buckeridge, J., and R.K. Dell. 1984. Personal communication. Elston, D.P., and S.L. Bressler. 1981. Magnetic stratigraphy of DVDP drill cores and late Cenozoic history of Taylor Valley, Transantarctic Mountains, Antarctica. In L.D. McGinnis (Ed.), Dry Valley Drilling Project. (Antarctic Research Series, Vol. 33.) Washington, D.C.: American Geophysical Union. Elston, D.P., and S.L. Bressler. In press. Paleomagnetism of MSSTS-1 core, McMurdo Sound, Antarctica. In I. McKenzie (Ed.), McMurdo Sound Sediment and Tectonic Studies. Wellington: New Zealand Department of Scientific and Industrial Research. Elston, D.P., P.H. Robinson, and S.L. Bressler. 1981. Stratigraphy, sedimentology, and paleomagnetism of the Coral Ridge sand body, eastern Taylor Valley, Antarctica. (U.S. Geological Survey Open-File Report Number 81-1303.) Harwood, D.M. 1984. Personal communication. Harwood, D.M. 1985. Personal communication. Harwood, D.M. In press. Upper Oligocene and Lower Miocene marine diatoms in glacial-marine sediments from the MSSTS-1 drill core, McMurdo Sound, Antarctica. In P. Barrett (Ed.), New Zealand Journal of Geology and Geophysics (Special volume). (McMurdo Sound Sediment and Tectonic Studies.) Newman, W. A., and A. Ross. 1971. Antarctic cirripedia. In W.A. Newman and A. Ross (Eds.), Antarctic Cirripedia. (Antarctic Research Series, Vol. 14.) Washington, D.C.: American Geophysical Union. Purucker, M.E., D.P. Elston, and S.L. Bressler. 1981. Magnetic stratigraphy of late Cenozoic glaciogenic sediments from drill cores, Taylor Valley, Transantarctic Mountains, Antarctica. In L. D. McGinnis (Ed.), Dry Valley Drilling Project. (Antarctic Research Series, Vol. 33.) Washington, D.C.: American Geophysical Union. Robinson, P.H. 1979. An investigation into the processes of entrainment, transportation and deposition of debris in polar ice, with special reference to the Taylor Glacier, Antarctica. (Doctoral thesis, Victoria University of
Wellington, New Zealand.)
Robinson, P.H. 1985. Preliminary report on the lithology and conditions of deposition of glaciogenic sediments from eastern Taylor Valley drill core, Antarctica. (New Zealand Geological Survey Report.)
Robinson, P.H., and A. Jaegars. 1984. The lithologic logs of eastern Taylor Valley (ETV) cores 2 to 13, southern Victoria Land, Antarctica. (New Zealand Geological Survey, Report G 89.) Lower Hutt: New Zealand Geological Survey.
17
P.H. ROBINSON New Zealand Geological Survey Lower Hutt, New Zealand
Work continues on this joint U.S./New Zealand multidisciplinary study of glacial deposits of the ice-free valleys in southern Victoria Land and of McMurdo Sound. Current studies in eastern (lower) Taylor Valley are aimed at developing detailed stratigraphic, paleomagnetic, and sedimentologic data from drill-core sections and are supplemented by paleontologic information provided by other workers. We hope to develop a better understanding of the Neogene glacial history of the region, particularly as it pertains to relationships between thickness and incursions of the Ross ice sheet, and potential correlations with changes in sea level and worldwide changes in climate. Our studies have been concentrated principally in eastern Taylor Valley, the only place amenable for the subsurface study of a thick series of interbedded glacial deposits of Ross Sea and continental (Taylor Glacier) origin. To date, 12 Winkie core holes, up to 70 meters in depth and totaling 485 meters of cored section, have been drilled along the length of the valley (figure 1). Drill-hole locations were selected to help answer questions
that arose during the analysis of Dry Valley Drilling Project (DVDP) cores drilled about a decade ago (see Elston and Bressler 1981; Elston, Robinson, and Bressler 1981; Purucker, Elston, and Bressler 1981). High core recovery and unbroken strings of core up to 3 meters in length, allowed us routinely to obtain oriented cores, thus permitting us to determine magnetic declinations as well as inclinations. Drilling has been conducted by the Antarctic Division of the New Zealand Department of Scientific and Industrial Research (DSIR). Sedimentological studies have been the responsibility of P.H. Robinson of the DSIR. Paleomagnetic studies, which include the determination of susceptibility and magnetic fabric as well as remanence, are being carried out by H.J. Rieck at the U.S. Geological Survey's paleomagnetics laboratory at Flagstaff. Detailed core logging and sampling have been a joint effort, conducted at the Thiel Earth Science Laboratory at McMurdo Station. Supporting paleontologic studies are being carried out by D. and T. Kellogg, University of Maine, Orono, and by D. Harwood, Institute of Polar Studies, Ohio State University. Lithostratigraphic and paleomagnetic correlations supported by sedimentologic and paleontologic data are being developed, but correlations are not yet final (see Robinson 1985). Paleomagnetic analysis of holes ETV-11, -12, and -13 is in progress. ("ETV" denotes "eastern Taylor Valley.") Lithologic logs of the cores at 1:200 scale have been published (Robinson and Jaegers 1984). Correlations shown on figure 2 reflect time lines derived from paleomagnetic and paleontologic data. Quality of stratigraphic information in the western part of the valley ranges from poor to good because of a variability in the ice cement encountered in sections drilled near the lakes. A second line of drill holes (open circles, figure 1) is planned for the western part of the valley for the 1986 - 1987 austral summer well away from the lakes. The objective will be to document in detail multiple incursions of the Ross ice sheet suggested from the previous drilling. These incursions may correlate with multiple, but currently undated, moraines and strand lines preserved locally near the western end of lower Taylor Valley. If correlations can be developed, the currently accepted picture of incursions of the Ross ice sheet during the past 500,000 or more years will become considerably more complicated. In
rlgure 1. Map showing locations of drill holes in eastern Taylor Valley, southern Victoria Land. ("km" denotes "kilometer?') 1985 REVIEW
15
LOWER TAYLOR VALLEY EAST
WEST Suess Meters Glacier 150
Lake Hoare
100
DVDP
Canada Glacier
New Harbor Meters ISO
Lake Fryxell ETV Ely ETV 59
ETV
ETV 12
50
ETV 10
ETV 13
low 50 tOO BASEMENT
Normal polarity
';:
Reverse polarity
I km approx. Poleomagnatic analysis in progress ------1 250
t±:
BRUNHESDVD
0
150
100
I ETV
Boundary between high and low McMu(do volcanic content
50 SEA LEVEL 0 SO 100 ISO ..200 250
Figure 2. Cross-section along axis of eastern Taylor Valley showing paleomagnetic polarity, visional correlations, and inferred ages of glacial strata. ("km" denotes "kilometer:')
addition, we will propose that the Longyear drill rig reoccupy the DVDP-11 drill site and complete coring of marine glacial deposits of Miocene and possibly greater age to the basement. Such information would enhance the likelihood of correlations with sections cored in the Ross Sea, and should provide information concerning the onset of accumulation of glacial sediments in the Taylor Valley fjord.
The Photogrammetric Section of the Branch of Astrogeology, U.S. Geological Survey, Flagstaff, has prepared a 1:25,000-scale topographic map of eastern Taylor Valley from recent (1983) aerial photographs. The contour interval of this map is 20 meters, with supplementary 10-meter contours in the valley floor. The master copy of the map is at the Reston, Virginia, offices of the National Mapping Division, U.S. Geological Sur-
Figure 3. Equal area plots of averaged directions of maximum magnetic susceptibility of samples from (A) basal till of Taylor Glacier (site mean declination 60.70, inclination - 8.1 0, alpha 95 19.50), and (B) water-laid glacial material near Lake Bonney (site mean declination 3.8 0, inclination —38.40, alpha 95 77.2 0). Arrows indicate direction of valley axis; X marks mean of direction of maximum magnetic susceptibility. Repeated measurements of invididual samples gave consistent results for A, and erratic results for B, indicating that B has very weak (if any) magnetic fabric. 16
ANTARCTIC JOURNAL
vey. This map will be used as a base for the preparation of a geologic map of glacial deposits in and adjacent to lower Taylor Valley. Five core holes, ETV-9 to -13 (figure 1), were drilled during the 1983 - 1984 austral summer. They ranged in depth from 16.9 meters to 70.9 meters. Holes ETV-10, -12, and -13 in more westerly parts of the valley penetrated terrestrial deposits of inferred Taylor Glacier (east antarctic) origin. Core near the bottom of hole ETV-10, from a depth of 67 to 70 meters, contains an assemblage of abundant barnacle and bivalve fragments, locally constituting as much as 30 percent of the core. This assemblage, which exhibits a low diversity, is dominated by the barnacle Bathylasma corolliforme (Hoek) and the bivalve Hiatella sp. (Buckeridge and Dell personal communications). However, only a few fragments of microfossils have been found in these beds (Harwood personal communication 1985). The barnacle, known in antarctic waters from strata of early Pleistocene to Recent age, provides a tentative maximum age for the fossiliferous beds in hole ETV-10 (Newman and Ross 1971). This, coupled with a preliminary polarity zonation for hole ETV-10 (figure 2), suggests a late Pliocene or early Pleistocene age for the strata, possibly correlative with the Olduvai normal polarity interval. Core from the CIROS-2 hole, drilled about 1 kilometer east of the terminus of Ferrar Glacier by the New Zealand DSIR in October and November 1984, has been sampled at Wellington by H. Rieck. The samples are currently being analyzed at the Flagstaff paleomagnetics laboratory. The objective is to provide polarity information to supplement paleontologic data for temporal evaluation. This work complements a recent reevaluation of the polarity zonation for McMurdo Sound Sediment and Tectonic Studies hole MSSTS-1 (Elston and Bressler in press) drilled in 1979. The polarity zonation from a depth of 116 meters to 226 meters in MSSTS-1 has been assigned to the late Oligocene on the basis of diatoms (Harwood personal communication 1984, 1985; Harwood in press), and the zonation has allowed the accumulation rate to be estimated for the interval 31 to 25 million years. Cores from the ETV drill holes in Taylor Valley are being analyzed by H. Rieck for magnetic fabric (anisotropy of magnetic susceptibility) with the objective of discriminating water-laid diamictons from ice-deposited glacial till. Magnetic fabric observed in the drill core is being evaluated with respect to control data obtained from oriented samples of basal till having known sedimentologic fabric (Robinson 1979) collected from near Taylor Glacier, and from water-laid deposits of Lake Bonney collected in upper Taylor Valley. The tills display a fabric having a shallow inclination that is aligned with the long axis of the valley, whereas the water-laid deposits characteristically display no anisotropy of susceptibility (figure 3).
185
REVIEW
This report is based upon work supported by National Science Foundation grant DPP 81-20877, and by the U.S. Geological Survey. The Antarctic Division, New Zealand Department of Scientific and Industrial Research, furnished the Winkie drill rig and drillers John Hay, Stephen Pilcher, Bruce Morris, and Warwick Potter, whose efforts are greatly appreciated. Gary Calderone, U.S. Geological Survey, ably assisted at the drill site and in the logging and sampling of cores.
References
Buckeridge, J., and R.K. Dell. 1984. Personal communication. Elston, D.P., and S.L. Bressler. 1981. Magnetic stratigraphy of DVDP drill cores and late Cenozoic history of Taylor Valley, Transantarctic Mountains, Antarctica. In L.D. McGinnis (Ed.), Dry Valley Drilling Project. (Antarctic Research Series, Vol. 33.) Washington, D.C.: American Geophysical Union. Elston, D.P., and S.L. Bressler. In press. Paleomagnetism of MSSTS-1 core, McMurdo Sound, Antarctica. In I. McKenzie (Ed.), McMurdo Sound Sediment and Tectonic Studies. Wellington: New Zealand Department of Scientific and Industrial Research. Elston, D.P., P.H. Robinson, and S.L. Bressler. 1981. Stratigraphy, sedimentology, and paleomagnetism of the Coral Ridge sand body, eastern Taylor Valley, Antarctica. (U.S. Geological Survey Open-File Report Number 81-1303.) Harwood, D.M. 1984. Personal communication. Harwood, D.M. 1985. Personal communication. Harwood, D.M. In press. Upper Oligocene and Lower Miocene marine diatoms in glacial-marine sediments from the MSSTS-1 drill core, McMurdo Sound, Antarctica. In P. Barrett (Ed.), New Zealand Journal of Geology and Geophysics (Special volume). (McMurdo Sound Sediment and Tectonic Studies.) Newman, W. A., and A. Ross. 1971. Antarctic cirripedia. In W.A. Newman and A. Ross (Eds.), Antarctic Cirripedia. (Antarctic Research Series, Vol. 14.) Washington, D.C.: American Geophysical Union. Purucker, M.E., D.P. Elston, and S.L. Bressler. 1981. Magnetic stratigraphy of late Cenozoic glaciogenic sediments from drill cores, Taylor Valley, Transantarctic Mountains, Antarctica. In L. D. McGinnis (Ed.), Dry Valley Drilling Project. (Antarctic Research Series, Vol. 33.) Washington, D.C.: American Geophysical Union. Robinson, P.H. 1979. An investigation into the processes of entrainment, transportation and deposition of debris in polar ice, with special reference to the Taylor Glacier, Antarctica. (Doctoral thesis, Victoria University of
Wellington, New Zealand.)
Robinson, P.H. 1985. Preliminary report on the lithology and conditions of deposition of glaciogenic sediments from eastern Taylor Valley drill core, Antarctica. (New Zealand Geological Survey Report.)
Robinson, P.H., and A. Jaegars. 1984. The lithologic logs of eastern Taylor Valley (ETV) cores 2 to 13, southern Victoria Land, Antarctica. (New Zealand Geological Survey, Report G 89.) Lower Hutt: New Zealand Geological Survey.
17
