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Variations in Detrital (Atmospheric Dust) Flux Within Icehouse Carbonates of Horseshoe Atoll (Pennsylvanian, West Texas)

Sohini Sur

School of Geology and Geophysics, University of Oklahoma, Norman

100 East Boyd st., Suite# 810, Norman, OK 73019

Email: [email protected]

Published studies of the detrital fraction through deep-sea cores of late Cenozoic age indicate that glacial intervals of the Cenozoic icehouse are generally associated with higher atmospheric dust flux. Furthermore, atmospheric dust influx and associated delivery of nutrients has been linked to boosts in primary productivity. We are investigating the hypothesis that detrital flux varied systematically as a result of glacial-interglacial climate fluctuations during the late Paleozoic icehouse, and might have driven shifts in productivity.

To test this hypothesis, we are studying Upper Pennsylvanian (Virgilian) cores from Horseshoe Atoll, a phylloid-algal carbonate buildup that formed in the Midland basin, far from fluvio-deltaic terrigenous influx. Samples at regular (1 m) intervals through several glacioeustatic sequences (15-30 m) exhibit distinct variations (0.01- 62%) in detrital fraction, with significant increases proximal to sequence boundaries (lowstands) and a crude upwardly coarsening trend (10-30 micron) within each sequence. Systematic changes in organic content and pyrite also occur. Increases in detrital fraction proximal to sequence boundaries reflects increased aridity and/or increased proximity/area of exposed land during glacials, whereas the upwardly coarsening trends within the sequences might reflect increased wind strength or source proximity. We are continuing research using additional approaches and samples to more thoroughly assess the presence and distinguish the cause(s) of these fluctuations in detrital flux. We are also investigating the possible relationship between detrital (atmospheric dust) flux and productivity in this system.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid