HR: 0800h
AN: T11D-0406    [Abstracts]
TI: Late Paleozoic Deglaciation in Western Equatorial Pangaea
AU: * Soreghan, G S
EM: lsoreg@ou.edu
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AU: Soreghan, M J
EM: msoreg@ou.edu
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AU: Eble, C F
EM: eble@kgs.mm.uky.edu
AF: Kentucky Geological Survey, University of Kentucky, Lexington, KY 40506
AU: Sweet, D
EM: dsweet@ou.edu
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AU: Davogustto, O
EM: dellpi@gmail.com
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AU: Young, R A
EM: ryoung@ou.edu
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AU: Elmore, R D
EM: delmore@ou.edu
AF: Geology & Geophysics, University of Oklahoma, 100 East Boyd Street, Norman, OK 73019
AB: The late Paleozoic icehouse is Earth's best-documented pre-Quaternary icehouse, long thought analogous to our modern world wherein glaciation is confined largely to high-latitude regions. However, emerging data from the Ancestral Rocky Mountains, an intraplate orogenic system in western equatorial Pangaea, indicate that glaciation extended to low latitudes as well. Key data exist in the Uncompahgre-uplift - Paradox basin system (western U.S.) in the form of a preserved Permo-Pennsylvanian glacial valley (ancestral Unaweep Canyon) and associated glacial and proglacial strata (proximal Cutler Formation). Within western Colorado, Unaweep Canyon is a deep, enigmatic, Precambrian-cored gorge that orthogonally bisects the western Uncompahgre Plateau, and is occupied by two underfit creeks flowing from a divide in its midst. A Cenozoic origin for the canyon is difficult to reconcile with geologic data; limited outcrop and well data confirm the canyon harbors a thick fill that includes a basal unit of probable late Paleozoic age as inferred by palynomorph, provenance, and preliminary paleomagnetic data. Geomorphologic attributes of the gorge walls together with preliminary results of cross-canyon gravity profiles indicate the canyon shape is best explained by a glacial genesis. Furthermore, the Permo-Pennsylvanian Cutler Formation onlaps Precambrian basement at the western mouth of the gorge, and contains facies of inferred proglacial (glaciolacustrine and glaciofluvial) origin, including (1) subaqueous sediment gravity flows, dropstones, and large slump blocks of an ice-contact Gilbert-type lacustrine delta, and (2) large-scale, laterally extensive cross-bedded conglomerates that record high-magnitude, outburst-type floods typical of deglaciation. The Cutler facies represent the proximal part of a system that ultimately extended to sea level in the distal Paradox basin. Maximum reasonable depositional gradients on this system yield maximum elevations of 500-1000 m for the glacial terminus, implying substantially cooler temperatures than the Quaternary and potentially more widespread glaciation than previously considered. Furthermore, preservation of this yoked uplift-basin system reflects subsidence of the Uncompahgre uplift sufficient to bury a landscape displaying > 1 km of relief, a remarkable result that implies substantial magnitudes and rates of tectonism of enigmatic origin in this intraplate system.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1699 General or miscellaneous
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
DE: 9615 Permian
SC: Tectonophysics [T]
MN: Fall Meeting 2005