RECONCILING THE TIMING, DURATION AND CHARACTER OF LATE PALEOZOIC GONDWANAN GLACIATIONS: RELEVANCE TO THE MIDCONTINENT NORTH AMERICAN STRATIGRAPHIC RECORD

Joint South-Central and North-Central Sections, both conducting their 41st Annual Meeting (11–13 April 2007)
Paper No. 17-2

Presentation Time: 8:20 AM-8:40 AM

RECONCILING THE TIMING, DURATION AND CHARACTER OF LATE PALEOZOIC GONDWANAN GLACIATIONS: RELEVANCE TO THE MIDCONTINENT NORTH AMERICAN STRATIGRAPHIC RECORD
FIELDING, Christopher R.¹, FRANK, Tracy D.², RYGEL, Michael C.³, BIRGENHEIER, Lauren P.⁴, ISBELL, John L.⁵, KOCH, Zelenda J.⁶, and HENRY, Lindsey C.⁵, (1) Department of Geosciences, Univ of Nebraska-Lincoln, 214 Bessey Hall, Lincoln, NE 68588-0340, cfielding2@unl.edu, (2) Department of Geosciences, University of Nebraska-Lincoln, 214 Bessey Hall, Lincoln, NE 68588, (3) Department of Geology, State University of New York at Potsdam, 44 Pierrepont Ave, Potsdam, NY 13676, (4) Department of Geosciences, University of Nebraska - Lincoln, 214 Bessey Hall, P.O. Box 880340, Lincoln, NE 68588-0340, (5) Dept. of Geosciences, University of Wisconsin, Milwaukee, WI 53211, (6) Dept. of Geosciences, Univ of Wisconisn, Milwaukee, 3209 N. Maryland Ave, Milwaukee, WI 53211 Recent studies of Carboniferous and Permian Gondwanan stratigraphic successions from eastern Australia and Antarctica suggest that multiple ice centers (ice caps and ice sheets) and alpine glaciers were active over discrete intervals during that time. This interpretation contrasts strongly with the dominant paradigm of the past thirty years, which invokes a protracted long-term glaciation involving permanent, continent-scale ice sheets. The emerging model of up to eight glacial intervals each 1-8 million years in duration, separated by non-glacial intervals of comparable duration, suggests long-term cyclic variation in climate mode throughout the late Paleozoic Ice Age. This long-term cyclicity discloses a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset in the mid-Carboniferous until an acme in the late Early Permian, followed by an opposite trend towards the final demise of glaciation in the earliest Late Permian. The glacial/non-glacial cyclicity is covariant with paleofloral change, eustatic sea-level fluctuations and CO2-surface temperature relationships for this interval. Calculations of ice volume based on geologically constrained estimates of ice sheet dimensions suggest that the magnitude of eustatic sea-level fluctuations during this time could have been no greater than 100 m, and in many cases may have been much less. These estimates are corroborated by data from sequence stratigraphic analysis of nearshore marine to coastal successions in ice-proximal locations. The new estimates of eustatic sea-level fluctuation are somewhat lower than some recent estimates based on cyclical (“cyclothemic”) successions and coastal onlap curves in North America, which were located far from direct ice influence. In this paper, we review evidence for sea-level fluctuation in the context of the Midcontinent North American stratigraphic record.
Joint South-Central and North-Central Sections, both conducting their 41st Annual Meeting (11–13 April 2007) General Information for this Meeting

Session No. 17 Sequence Stratigraphy and Biostratigraphy of Pennsylvanian–Lower Permian Cyclothems in the North American Midcontinent I Kansas Union, University of Kansas: Alderson Auditorium 8:00 AM-12:00 PM, Thursday, 12 April 2007 Geological Society of America Abstracts with Programs, Vol. 39, No. 3, p. 19
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