A 2 million year glacial chronology of the Hatherton Glacier, Antarctica and implications for the size of the East Antarctic Ice Sheet at the Last Glacial Maximum

摘要

A series of distinct glacial deposits flanking the margins of the upper Hatherton Glacier, an outlet glacier in the central Transantarctic Mountains, are used to constrain the behaviour of the Antarctic ice-sheets. Cosmogenic exposure ages of 18 erratics from four glacial drifts covering the ice free Dubris and Bibra valleys, range in age from 5 to 1997 ka. Our results document four glacial advance and retreat events superimposed on an overall long-term ice thickness reduction of about 500 m since the mid-Pleistocene. The lack of field evidence and absence of LGM exposure ages in the glacial deposits of the Hatherton Glacier supports our conclusion that at the LGM the East Antarctic Ice Sheet was of similar size, or may have been slightly smaller, than present. Minimum exposure ages from the oldest two glacial events, represented by the Isca and Danum drifts, are~1-2 Ma and ~0.5 Ma respectively. The Britannia-II Drift, previously assumed to mark the maximum extent of the Last Glacial Maximum advance, has a mean 10Be age of 126 ± 3.2 ka (n = 5). Ages from the younger Britannia-I Drift suggest that since the mid-Holocene (6.5 ± 1.2 ka, n = 5), approximately 200 m of additional ice has been lost.