Late Cenozoic glacial history of the Terra Nova Bay Region, northern Victoria Land, Antarctica

OROMBELLI G. , BARONI C. & DENTON G.H ., Late Cenozoic glacial history of the Terra Nova Bay region, northern Victoria Land, A ntarctica, (IT ISSN 0391-9838, 1990) Glacial geological and geomorphological research in the Terra Nova Bay region was undertaken to decipher late Cenozoic ice-sheet behavior in northern Victoria Land. The work is part of a continuing program to understand and anticipate the response of the Antarctic Ice Sheet to climatic change. The Transantarctic Mountains inland of Terra Nova Bay exhibit four major landscapes. 1) The first type consists of deep troughs propagated inland by headward cutting. The lower portions of these troughs form ice-covered fjords, where present-day grounding lines extend inland beneath outlet glaciers. 2) Well-developed alpine glacial topography (with cirques, ridges, horns, and spurs) characterizes the region. Alpine topography has propagated from the deep troughs into the intervening mountain blocks. This morpholog y can locally be very old and reflects a different-from-present climatic regime. Furthermore, the formation of the alpine topograpy and of the glacial troughs did not require an East Antarctic Ice Sheet. 3) Relict summit mesas occur in the high central mountain ranges between troughs. Thin ice caps cover the central mesa topography and commonly spill over the mesa edges to feed cirque or tributary glaciers within the alpine topography. 4) The fourth type of morphology features undulating coastal piedmonts that are tilted seaward. The process of inland erosion by outlet glacier troughs and adjacent alpine topography has left isolated nearly intact remnants of the original topograph y. Near the coast , these remnants include the coastal piedmonts; farther inland they include the summit mesas. Trimlines superimposed on the alpine and outlet-trough topography mark the maximum possible expansion of the northern Victoria Land ice cover since erosion of the alpine topography. This expansion (*) Dipartimento di Scienze della Terra, Uniuersita di Milano and Centro di Studio per la Stratigra/ia e la Petrogra/ia delle Alpi Centrali, CNR, Milano (Italy). . ( 'h~ ) Museo Civico di Scienze Naturali, Brescia (Italy). (* ,~ *) Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono , Maine (USA). The f ield research was supported [ointly by Programma Nazionale di Ricerche in Antartide (Italy) and the Division of Polar Programs of the National Science Foundation (United States). New Zealand Helicopters Ltd. provided helicopter support under contract to Programma Nazionale di Ricerche in A ntartide. Data analysis by G. OROMBELLI and C. BARONIwas fi nancially supported by ENEA through a joint research program on A ntarctic Earth Sciences with the University of Siena. Data analysis by G .H . DENTON was f unded by the global change program of NOAA as part ofa study to determine the response of the East Antarctic Ice Sheet to global warming. 5 values ofburied icefrom ice-cored drift were k indly supplied by A. LONGINELLI (University ofTrieste). T.B. KELLOGG and J.F. SPLETTSTOESSER provided helpful comments on the manuscript. was minor in the upper reaches of outlet glaciers and in mountain accumulation areas while it represented great thickening in the coastal area. There is no definitive evidence that the East Antarctic Ice Sheet overrode northern Victori a Land nunataks or mountains. Several glacial drifts have been differentiated. Terra Nova drift (late Wisconsin) is well-exposed and preserved along coastal ice-free areas, where it was cut beginning 7 000-8 000 yr B.P. by beaches now up to 30 m above present sea level. The Terra Nova drift limit can be tr aced far inland along the main glaciers. During late Wisconsin time , the glacier thickening was greatest in coastal regions , where a grounded piedmont glacier filled Terra Nova Bay. The Terra Nova piedmont glacier was probably part of a marine-based ice sheet in the inner Ross Embayment. High-elevation striations in the Eisenhower Range seem to have been carved during Terra Nova glaciation. If so, local mesa ice caps and mountain glaciers expanded to feed the Terra Nova piedmont glacier duri ng late Wisconsin time , unlike the situation farther south where alpine glacier termini in the Dry Valleys were less extensive than now during late Wisconsin time.