Antarctic Glacial Chronology: New Constraints from Surface Exposure Dating

Surface exposure dating using 3He, Ne-21 and Cl-36 combined with mapping of moraines, provide new constraints on West Antarctic Ice Sheet (WAIS) chronology. New He-3 production rates are determined from a 125 ka lava flow. Measurements of inherited He-3/He-4 in two common Antarctic lithologies allow...

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Bibliographic Details
Main Author: Ackert, Robert P., Jr
Other Authors: MASSACHUSETTS INST OF TECH CAMBRIDGE
Format: Text
Language:English
Published: 2000
Subjects:
Astrophysics
*COSMIC RAYS
THESES
EROSION
STRATIGRAPHY
ICE
CLIMATE
EARTH SURFACE
SEA LEVEL
ANTARCTIC REGIONS
GLACIERS
NUCLIDES
LITHOLOGY
COSMOGENIC NUCLIDES
Antarctic
West Antarctic Ice Sheet
Beardmore
Beardmore Glacier
Koettlitz Glacier
Antarc*
Ice Sheet
Online Access:http://www.dtic.mil/docs/citations/ADA390281
http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA390281
Description
Summary:Surface exposure dating using 3He, Ne-21 and Cl-36 combined with mapping of moraines, provide new constraints on West Antarctic Ice Sheet (WAIS) chronology. New He-3 production rates are determined from a 125 ka lava flow. Measurements of inherited He-3/He-4 in two common Antarctic lithologies allow measurement of exposure ages < 6000 years. At Mt. Waesche, a moraine band records interior WAIS elevations higher than present. Surface exposure ages indicate that the last ice highstand occurred 10 +/- 1 ka. The data constrain past WAIS behavior and ice volume. Surface exposure ages place age constraints on six Beardmore Glacier drifts. Two drifts record damming of the glacier during the last glacial maximum (10-20 ka) by an expanded WAIS. The four older drifts record similar damming by the WAIS approx. 600 ka, approx. 1 Ma, and approx. 2 Ma. Moraines of Koettlitz Glacier also record damming by the WAIS prior to the LGM. The oldest moraines are > 400 ka. Independent stratigraphic control allows evaluation of prior exposure, cover and determination of erosion rates. Taken together, the results are consistent with sea level control of WAIS extent; the WAIS probably has fluctuated synchronously with the Northern Hemisphere ice sheets for at least the last 1 million years. --Original contains color plates: All DTIC reproductions will be in black and white. Prepared in cooperation with Woods Hole Oceanographic Institution, Woods Hole, MA>

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