|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
,1
1 Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA
2 Department of Geosciences, North Dakota State University, Fargo, North Dakota 58105, USA
3 Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA
We present a glacial record from the western Olympus Range, East Antarctica, that documents a permanent shift in the thermal regime of local glaciers, from wet- to cold-based regimes, more than 13.94 m.y. ago. This glacial record provides the first terrestrial evidence linking middle Miocene global climate cooling to a permanent reorganization of the Antarctic cryosphere and to subsequent growth of the polar East Antarctic Ice Sheet. The composite stratigraphic record constructed from field mapping and analyses of 281 soil excavations shows a classic wet-based till (Circe till, including an extensive melt-out facies), overlain by a weathered colluvial deposit (Electra colluvium), and then a series of stacked tills deposited from cold-based ice (Dido drift). Chronologic control comes from 40Ar/39Ar analyses of concentrated ash-fall deposits interbedded within glacial deposits. The shift from wet- to cold-based glaciation reflects a drop in mean annual temperature of 25–30 °C and is shown to precede one or more major episodes of ice-sheet expansion across the region, the youngest of which occurred between 13.62 and 12.44 Ma. One implication is that atmospheric cooling, following a relatively warm mid-Miocene climatic optimum ca. 17 to 15 Ma, may have led to, and thus triggered, maximum ice-sheet overriding.
Key Words: alpine glaciers • geomorphology • Dry Valleys • Miocene • till • volcanic ash • Antarctica • Olympus Range • cold-based glaciers
This article has been cited by other articles:
|
|
 |
|
  K. C. Maguire and A. L. Stigall Using ecological niche modeling for quantitative biogeographic analysis: a case study of Miocene and Pliocene Equinae in the Great Plains Paleobiology, December 1, 2009; 35(4): 587 - 611. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. McKay, G. Browne, L. Carter, E. Cowan, G. Dunbar, L. Krissek, T. Naish, R. Powell, J. Reed, F. Talarico, et al. The stratigraphic signature of the late Cenozoic Antarctic Ice Sheets in the Ross Embayment Geological Society of America Bulletin, November 1, 2009; 121(11-12): 1537 - 1561. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Warny, R. A. Askin, M. J. Hannah, B. A.R. Mohr, J. I. Raine, D. M. Harwood, F. Florindo, and the SMS Science Team Palynomorphs from a sediment core reveal a sudden remarkably warm Antarctica during the middle Miocene Geology, October 1, 2009; 37(10): 955 - 958. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. E. Chapin Interplay of oceanographic and paleoclimate events with tectonism during middle to late Miocene sedimentation across the southwestern USA Geosphere, December 1, 2008; 4(6): 976 - 991. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. R. Lewis, D. R. Marchant, A. C. Ashworth, L. Hedenas, S. R. Hemming, J. V. Johnson, M. J. Leng, M. L. Machlus, A. E. Newton, J. I. Raine, et al. Mid-Miocene cooling and the extinction of tundra in continental Antarctica PNAS, August 5, 2008; 105(31): 10676 - 10680. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
