Dry valleys/McMurdo Sound magnetostratigraphy and sedimentology
References
Denton, C. H., R. L. Armstrong, M. Stuiver. 1971. The Late Cenozoic glacial history of Antarctica. In K. K. Turekian (Ed.), Late Cenozoic glacial ages. New Haven and London: Yale University Press. Dreimanis, A. 1976. Tills: Their origin and properties. In Legget, R. F. (Ed.), Glacial till. (Special publication 12, 11-49). Ottawa: Royal Society of Canada. Folk, R. L. 1954. The distinction between grain size and mineral corn-
Dry valleys/McMurdo Sound magnetostratigraphy and sedimentology DONALD P. ELSTON and HUGH J . RIECK U.S. Geological Survey Flagstaff Arizona 86001
PAUL H. ROBINSON New Zealand Geological Survey Department of Scientific and Industrial Research Lower Hutt, New Zealand
A continuing, international multidisciplinary investigation of the late Cenozoic history of the dry valleys and McMurdo Sound region, southern Victoria Land, includes Winkie core drilling, logging, and sampling of cores for paleomagnetic, paleontologic, and sedimentologic analysis and detailed geo-
position in sedimentary-rock nomenclature. Journal of Geology, 64(2), 344-359. Hendy, C. H., T. R. Healy, E. M. Rayner, J. Shaw, A. T. Wilson. 1979. Late Pleistocene glacial chronology of the Taylor Valley, and the global climate. Quaternary Research, 11, 172-184. Robinson, P. H. 1979. An investigation into the processes of entrainment, transportation and deposition of debris in polar ice, with special reference to Taylor Glacier, Antarctica. Unpublished doctoral dissertation, Victoria
University of Wellington. Shaw, J. 1977. Till body morphology and structure related to glacier flow. Boreas, 6(2), 189-201.
logic mapping of the glacial deposits. Work carried out during the 1980-1981 and 1982-1983 field seasons has been concentrated in lower (eastern) Taylor Valley, and a third effort is planned for the 1983-1984 field season. Objectives are to (1) develop a detailed stratigraphy in the near-subsurface, tied to surface exposures, so that the character and extent of incursions of the Ross Ice Sheet into Taylor Valley can be better understood, (2) refine age determinations of the glacigenic sediments by employing polarity and paleontologic information, and (3) tie the subsurface and surface records in Taylor Valley to subsurface records in McMurdo Sound. Information gained by meeting these objectives should lead to a better understanding of the glacial history of southern Victoria Land and the Ross Ice Sheet and should enable scientists to evaluate potential relationships to global changes in sea level and climate. During the 1982-1983 field season, six core holes (ETV-3 to -8; figure 1), ranging in depth from 10.5 to 58 meters (figure 2), were drilled in ice-cemented deposits in eastern Taylor Valley. Additionally, detailed geologic mapping (1:24,000 scale) was begun, with the geology ultimately to be compiled on a new, detailed topographic base map to be made photogrammetrically from new aerial photographs flown during the 1982-1983 field season. Approximately 255 samples were col-
Figure 1. Map of eastern (lower) Taylor Valley showing locations of Dry Valley Drill Project (DVDP) and Winkle (ETV) core drill holes.
1983 REVIEW
29
WEST
EAST
cIJ
dr - drift $ - sand
>
I—
N-
ps - pebbly sand
I > —In I—
di - diamicton
U
U
—80 —J a
' 4 A 4 '? 449 ' 2 A
dr
> ILU
0
A
,
U)
S.
I\ > I I l\ ILii/7
di
0
U)
ps
> -
?\ : \\\
I
LU
dl 2
BRUNHES 10.6 585
4
m
;
I
Sea Level
79C
SCALE
'
4 5800 y. B.P.
20
Meters
10 200 600 1000
Meters
27.8
328 m (TD)
55
186 m(TD)
Figure 2. Longitudinal section in eastern part of lower Taylor Valley showing generalized stratigraphic correlations in the glacigenic sediments derived from lithostratigraphy, sedimentology, and magnetostratigraphy. Brunhes-age diatoms have been identified from across the ETV core sections (see text). Unit numbers for the ETV sections are lithostratigraphic units recognized from mapping, from detailed lithologic logging, and from sedimentologic analysis. The polarity switch marking the apparent base of normally polarized deposits of Brunhes age (less than about 730,000 years) is given for reference to figure 3. ("BA" denotes before present.)
lected for paleomagnetic analysis, 85 samples for sedimentologic analysis, 20 samples for paleontologic (diatom) analysis, and 10 samples for geochemical analysis. Detailed geologic logs of the drill cores were made at McMurdo Station prior to the sampling of the cores. Some individual core runs were recovered with known azimuthal orientations, the object being to obtain information on secular variation of the magnetic field. Moreover, work is to be undertaken in an attempt to relate magnetic fabric to sedimentary fabric to provide additional information for the interpretation of depositional environments. Sedimentologic analysis of the ETV drill cores (by Robinson) has been completed and a report prepared for review. Figure 2 summarizes the several, apparently correlative; units that have emerged from evaluating the sedimentologic data with respect to the detailed lithologic logs. The youngest deposit is sand (unit 1, ETV-4), physically correlative with Recent sand at New Harbor. This unit overlaps drift that is related to the last incursion of the Ross Ice Sheet (Ross I of Denton, Armstrong, and Stuiver 1971), a drift that extensively veneers the floor and lower walls of Taylor Valley (unit 1 of ETV-3, and -1 and -2, -5, and -6). The underlying units are dominantly ice-cemented sand, pebbly sand, and interbedded diamicton. The sand appears to have largely accumulated in a fluviatile environment. Because the 30
sand appears to become finer to the west, a Ross Ice Sheet lying to the east seems indicated for the source of the water and the detritus. The diamicton-like deposits (unit 4, ETV-2 and 3, and unit 2, ETV-8) have textural characteristics similar to modern flow till and melt-out till studied along the margin of Taylor Glacier, and these sediments thus are believed to have been derived from an ice contact environment, presumably the base or margin of a glacier. Additionally, the stratigraphy and provisional correlations developed to date suggest some cyclicity in depositional environments through time. Preliminary interpretation of the lithologic sections suggests at least two incursions of Ross Sea ice separated by the accumulation of proglacial sandur, fluviatile, and lacustrine deposits. Diatom studies from samples of the cores are being conducted by Davida and Thomas Kellogg, University of Maine, who report (personal communication) data bearing on the age and environment of deposition of the subsurface units (with many of the samples collected from ETV-3). They find that (1) nonmarine species predominate in all samples and are in a much better state of preservation than the marine specimens, (2) marine fragments are present in most samples, suggesting perhaps repeated reworking, and (3) diatoms of Brunhes age (less than 730,000 years) are found across the drill core sections, the deposits of which thus are considered to be no older than ANTARCTIC JOURNAL
LOWER TAYLOR VALLEY WEST Suess Meters Glacier 150
Lolte Hoare
EAST New Harbor Meters ISO
Canada Glacier
50 _J AII 50 10 150 I:M'IaaI
100
DVDP
ETV
ETV ETV ETV \DVDP
00 ETV
50
IMTUYAMA? GAUSS ?
i
100
PLIOCENE /sl/OCENE
-
I
200
ISO
1 200 250
250
Figure 3. Longitudinal section along lower Taylor Valley showing polarity zonations, magnetostratigraphic correlations, and ages for drill core sections. Black denotes normal polarity; white denotes reverse polarity. Potentially, a major unconformity may be present at the base of apparent Brunhes-age deposits in the eastern part of the valley, which rest on reverse polarity deposits that could be as old as Gilbert (about 3.3 million years and older).
Brunhes even though they contain some specimens indicative of a Miocene age. The Kelloggs suggest that the sections penetrated by the drill accumulated as a sequence of nonmarine deposits, possibly deltas, which contain reworked marine material derived from former Ross Sea drift. Paleomagnetic studies of core and outcrop samples, although incomplete, have progressed far enough to resolve the question as to the polarity of surface deposits and subsurface deposits that closely (approximately 60 meters) underlie the Ross Sea drift. All samples are of normal polarity (figure 3), in accord with the Brunhes age reported from diatoms. The vexing problem of an interval of reversed polarity in core from Dry Valley Drilling Project (DVDP) hole 11 at a depth of about 2 to 4 meters (Elston and Bressler, 1981; Elston, Robinson, and Bressler 1981, Purucker, Elston, and Bressler 1981) has been resolved. Only normal polarity has been obtained from shallow ETV cores that were drilled in the vicinity of and closely adjacent to hole DVDP-11. Additionally, an exposure was excavated near DVDP-11, from which oriented samples also were collected. These, too, proved to be normally polarized. The reported interval of reverse polarity in the upper part of the DVDP-11 section thus now has been discarded. The cause for the anomalous reverse polarity in the upper part of the DVDP-11 section is not known, but it may have been produced by inversion of parts of the core sometime during handling, an inversion that had been specifically looked for, but not detected, during an inspection of the core at the Antarctic Core Storage Facility, Tallahassee, Florida.
1983 REVIEW
This work is supported by National Science Foundation grant 81-20877; by the Antarctic Division, New Zealand Department of Scientific and Industrial Research, which furnished the Winkie drill rig and a field staff consisting of James Jenkins, Roy Parish, Greg Ryan, and Lou Sanson; and by the U.S. Geological Survey. DPP
References Denton, C. H., R. L. Armstrong, and M. Stuiver. 1971. The late Cenozoic glacial history of Antarctica. In E. E. Turekian (Ed.), The Late Cenozoic glacial ages. New Haven, Conn.: Yale University Press. 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., 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) Washington, D.C.: U.S. Government Printing Office. Kellogg, D., and T. Kellogg. 1983. Personal communication. 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.
31
Denton, C. H., R. L. Armstrong, M. Stuiver. 1971. The Late Cenozoic glacial history of Antarctica. In K. K. Turekian (Ed.), Late Cenozoic glacial ages. New Haven and London: Yale University Press. Dreimanis, A. 1976. Tills: Their origin and properties. In Legget, R. F. (Ed.), Glacial till. (Special publication 12, 11-49). Ottawa: Royal Society of Canada. Folk, R. L. 1954. The distinction between grain size and mineral corn-
Dry valleys/McMurdo Sound magnetostratigraphy and sedimentology DONALD P. ELSTON and HUGH J . RIECK U.S. Geological Survey Flagstaff Arizona 86001
PAUL H. ROBINSON New Zealand Geological Survey Department of Scientific and Industrial Research Lower Hutt, New Zealand
A continuing, international multidisciplinary investigation of the late Cenozoic history of the dry valleys and McMurdo Sound region, southern Victoria Land, includes Winkie core drilling, logging, and sampling of cores for paleomagnetic, paleontologic, and sedimentologic analysis and detailed geo-
position in sedimentary-rock nomenclature. Journal of Geology, 64(2), 344-359. Hendy, C. H., T. R. Healy, E. M. Rayner, J. Shaw, A. T. Wilson. 1979. Late Pleistocene glacial chronology of the Taylor Valley, and the global climate. Quaternary Research, 11, 172-184. Robinson, P. H. 1979. An investigation into the processes of entrainment, transportation and deposition of debris in polar ice, with special reference to Taylor Glacier, Antarctica. Unpublished doctoral dissertation, Victoria
University of Wellington. Shaw, J. 1977. Till body morphology and structure related to glacier flow. Boreas, 6(2), 189-201.
logic mapping of the glacial deposits. Work carried out during the 1980-1981 and 1982-1983 field seasons has been concentrated in lower (eastern) Taylor Valley, and a third effort is planned for the 1983-1984 field season. Objectives are to (1) develop a detailed stratigraphy in the near-subsurface, tied to surface exposures, so that the character and extent of incursions of the Ross Ice Sheet into Taylor Valley can be better understood, (2) refine age determinations of the glacigenic sediments by employing polarity and paleontologic information, and (3) tie the subsurface and surface records in Taylor Valley to subsurface records in McMurdo Sound. Information gained by meeting these objectives should lead to a better understanding of the glacial history of southern Victoria Land and the Ross Ice Sheet and should enable scientists to evaluate potential relationships to global changes in sea level and climate. During the 1982-1983 field season, six core holes (ETV-3 to -8; figure 1), ranging in depth from 10.5 to 58 meters (figure 2), were drilled in ice-cemented deposits in eastern Taylor Valley. Additionally, detailed geologic mapping (1:24,000 scale) was begun, with the geology ultimately to be compiled on a new, detailed topographic base map to be made photogrammetrically from new aerial photographs flown during the 1982-1983 field season. Approximately 255 samples were col-
Figure 1. Map of eastern (lower) Taylor Valley showing locations of Dry Valley Drill Project (DVDP) and Winkle (ETV) core drill holes.
1983 REVIEW
29
WEST
EAST
cIJ
dr - drift $ - sand
>
I—
N-
ps - pebbly sand
I > —In I—
di - diamicton
U
U
—80 —J a
' 4 A 4 '? 449 ' 2 A
dr
> ILU
0
A
,
U)
S.
I\ > I I l\ ILii/7
di
0
U)
ps
> -
?\ : \\\
I
LU
dl 2
BRUNHES 10.6 585
4
m
;
I
Sea Level
79C
SCALE
'
4 5800 y. B.P.
20
Meters
10 200 600 1000
Meters
27.8
328 m (TD)
55
186 m(TD)
Figure 2. Longitudinal section in eastern part of lower Taylor Valley showing generalized stratigraphic correlations in the glacigenic sediments derived from lithostratigraphy, sedimentology, and magnetostratigraphy. Brunhes-age diatoms have been identified from across the ETV core sections (see text). Unit numbers for the ETV sections are lithostratigraphic units recognized from mapping, from detailed lithologic logging, and from sedimentologic analysis. The polarity switch marking the apparent base of normally polarized deposits of Brunhes age (less than about 730,000 years) is given for reference to figure 3. ("BA" denotes before present.)
lected for paleomagnetic analysis, 85 samples for sedimentologic analysis, 20 samples for paleontologic (diatom) analysis, and 10 samples for geochemical analysis. Detailed geologic logs of the drill cores were made at McMurdo Station prior to the sampling of the cores. Some individual core runs were recovered with known azimuthal orientations, the object being to obtain information on secular variation of the magnetic field. Moreover, work is to be undertaken in an attempt to relate magnetic fabric to sedimentary fabric to provide additional information for the interpretation of depositional environments. Sedimentologic analysis of the ETV drill cores (by Robinson) has been completed and a report prepared for review. Figure 2 summarizes the several, apparently correlative; units that have emerged from evaluating the sedimentologic data with respect to the detailed lithologic logs. The youngest deposit is sand (unit 1, ETV-4), physically correlative with Recent sand at New Harbor. This unit overlaps drift that is related to the last incursion of the Ross Ice Sheet (Ross I of Denton, Armstrong, and Stuiver 1971), a drift that extensively veneers the floor and lower walls of Taylor Valley (unit 1 of ETV-3, and -1 and -2, -5, and -6). The underlying units are dominantly ice-cemented sand, pebbly sand, and interbedded diamicton. The sand appears to have largely accumulated in a fluviatile environment. Because the 30
sand appears to become finer to the west, a Ross Ice Sheet lying to the east seems indicated for the source of the water and the detritus. The diamicton-like deposits (unit 4, ETV-2 and 3, and unit 2, ETV-8) have textural characteristics similar to modern flow till and melt-out till studied along the margin of Taylor Glacier, and these sediments thus are believed to have been derived from an ice contact environment, presumably the base or margin of a glacier. Additionally, the stratigraphy and provisional correlations developed to date suggest some cyclicity in depositional environments through time. Preliminary interpretation of the lithologic sections suggests at least two incursions of Ross Sea ice separated by the accumulation of proglacial sandur, fluviatile, and lacustrine deposits. Diatom studies from samples of the cores are being conducted by Davida and Thomas Kellogg, University of Maine, who report (personal communication) data bearing on the age and environment of deposition of the subsurface units (with many of the samples collected from ETV-3). They find that (1) nonmarine species predominate in all samples and are in a much better state of preservation than the marine specimens, (2) marine fragments are present in most samples, suggesting perhaps repeated reworking, and (3) diatoms of Brunhes age (less than 730,000 years) are found across the drill core sections, the deposits of which thus are considered to be no older than ANTARCTIC JOURNAL
LOWER TAYLOR VALLEY WEST Suess Meters Glacier 150
Lolte Hoare
EAST New Harbor Meters ISO
Canada Glacier
50 _J AII 50 10 150 I:M'IaaI
100
DVDP
ETV
ETV ETV ETV \DVDP
00 ETV
50
IMTUYAMA? GAUSS ?
i
100
PLIOCENE /sl/OCENE
-
I
200
ISO
1 200 250
250
Figure 3. Longitudinal section along lower Taylor Valley showing polarity zonations, magnetostratigraphic correlations, and ages for drill core sections. Black denotes normal polarity; white denotes reverse polarity. Potentially, a major unconformity may be present at the base of apparent Brunhes-age deposits in the eastern part of the valley, which rest on reverse polarity deposits that could be as old as Gilbert (about 3.3 million years and older).
Brunhes even though they contain some specimens indicative of a Miocene age. The Kelloggs suggest that the sections penetrated by the drill accumulated as a sequence of nonmarine deposits, possibly deltas, which contain reworked marine material derived from former Ross Sea drift. Paleomagnetic studies of core and outcrop samples, although incomplete, have progressed far enough to resolve the question as to the polarity of surface deposits and subsurface deposits that closely (approximately 60 meters) underlie the Ross Sea drift. All samples are of normal polarity (figure 3), in accord with the Brunhes age reported from diatoms. The vexing problem of an interval of reversed polarity in core from Dry Valley Drilling Project (DVDP) hole 11 at a depth of about 2 to 4 meters (Elston and Bressler, 1981; Elston, Robinson, and Bressler 1981, Purucker, Elston, and Bressler 1981) has been resolved. Only normal polarity has been obtained from shallow ETV cores that were drilled in the vicinity of and closely adjacent to hole DVDP-11. Additionally, an exposure was excavated near DVDP-11, from which oriented samples also were collected. These, too, proved to be normally polarized. The reported interval of reverse polarity in the upper part of the DVDP-11 section thus now has been discarded. The cause for the anomalous reverse polarity in the upper part of the DVDP-11 section is not known, but it may have been produced by inversion of parts of the core sometime during handling, an inversion that had been specifically looked for, but not detected, during an inspection of the core at the Antarctic Core Storage Facility, Tallahassee, Florida.
1983 REVIEW
This work is supported by National Science Foundation grant 81-20877; by the Antarctic Division, New Zealand Department of Scientific and Industrial Research, which furnished the Winkie drill rig and a field staff consisting of James Jenkins, Roy Parish, Greg Ryan, and Lou Sanson; and by the U.S. Geological Survey. DPP
References Denton, C. H., R. L. Armstrong, and M. Stuiver. 1971. The late Cenozoic glacial history of Antarctica. In E. E. Turekian (Ed.), The Late Cenozoic glacial ages. New Haven, Conn.: Yale University Press. 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., 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) Washington, D.C.: U.S. Government Printing Office. Kellogg, D., and T. Kellogg. 1983. Personal communication. 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.
31
