The Mount Feather Diamicton of the Sirius Group: an accumulation of indicators of Neogene Antarctic glacial and climatic history

Authors

G. A. Wilson, University of Oxford, Parks Road, Oxford OX1 3PR, UK
J. A. Barron, United States Geological Survey, MS 915, 345 Middle¢eld Road, Menlo Park, CA
A. C. Ashworth, North Dakota State University, Fargo, ND
R. A. Askin, Byrd Polar Research Center, The Ohio State University, 1090 Carmack Road, Columbus, OH
J. A. Carter, School of Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand
M. G. Curren, Florida State University
D. H. Dalhuisen, Faculty of Civil Engineering, Delft University of Technology, Delft, The Netherlands
E. I. Friedmann, Space Sciences Division, NASA Ames Research Center, MailCode 245-3, Mo¡ett Field, CA
D. G. Fyodorov-Davidov, Institute of SoilScience and Cryology, Russian Academy of Sciences, Puschino, Moscow Region 142292, Russia
D. A. Gilichinsky, Institute of SoilScience and Cryology, Russian Academy of Sciences, Puschino, Moscow Region 142292, Russia
M. A. Harper, School of Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand
David M. Harwood, University of Nebraska-LincolnFollow
J. F. Hiemstra, University of Glasgow
T. R. Janecek, Florida State University
K. J. Licht, Indiana University, Purdue University Indianapolis
V. E. Ostroumov, Institute of SoilScience and Cryology, Russian Academy of Sciences, Puschino, Moscow Region 142292, Russia
R. D. Powell, Northern Illinois UniversityFollow
E. M. Rivkina, Institute of SoilScience and Cryology, Russian Academy of Sciences, Puschino, Moscow Region 142292, Russia
S. A. Rose, University of Nebraska-Lincoln
A. P. Stroeven, Stockholm University
P. Stroeven, Faculty of Civil Engineering, Delft University of Technology, Delft, The Netherlands
J. J. M. van der Meer, Queen Mary and West¢eld College, University of London
M. C. Wizevich, Cornell University

Date of this Version

7-14-2002

Comments

Published in Palaeogeography, Palaeoclimatology, Palaeoecology 182 (2002) 117-131.

Abstract

A paucity of data from the Antarctic continent has resulted in conflicting interpretations of Neogene Antarctic glacial history. Much of the debate centres on interpretations of the glacigene Sirius Group strata that crop out as discrete deposits along the length of the Transantarctic Mountains and in particular on its age and the origin of the siliceous microfossils it encloses. Pliocene marine diatoms enclosed within Sirius Group strata are inferred to indicate a dynamic East Antarctic ice sheet that was much reduced, compared with today, in the early-middle Pliocene and then expanded again in the late Pliocene. However, the geomorphology of the Dry Valleys region is interpreted to represent a relatively long-lived (middle Miocene-recent) and stable polar climatic regime similar to that of today. The Mount Feather Diamicton infills a palaeovalley at ca. 2500 m on the NE flank of Mount Feather in the Dry Valleys region and has been included within the Sirius Group. We obtained four shallow cores (COMRAC 8, 9, 10 and 11) from beneath the permafrost boundary in the Mount Feather Diamicton in order to understand its origin and relationship with the surrounding landscape. Detailed studies of these cores (stratigraphy, sedimentology, palaeontology, micromorphology, petrography and fabric) have yielded new data that demonstrate a much more complex climatic and glacial history for the Mount Feather Diamicton than in previous interpretations. The data indicate that the Mount Feather Diamicton was deposited beneath a wet based glacier fed from a larger ice sheet behind the Transantarctic Mountains. It is, however, unlikely that this ice sheet overtopped Mount Feather (2985 m). A near-in situ non-marine diatom assemblage was recovered from 90 cm depth in COMRAC 10 and indicates a maximum depositional age of Late Miocene for the Mount Feather Diamicton. A subsequent glacial episode has distributed a boulder blanket across the surface of the diamicton. Other post-depositional processes include drying, infilling of surface layers with aeolian sediment, and the development of melt-water runnels. We interpret these combined data to indicate the persistence of more temperate climatic and glacial conditions in the vicinity of Mount Feather until at least the Late Miocene.