VARIATIONS IN ATMOSPHERIC DUST FLUX RECORDED IN UPPER PENNSYLVANIAN CARBONATES OF HORSESHOE ATOLL, MIDLAND BASIN, TEXAS

Studies of deep sea eolian records of Quaternary age show increases in atmospheric dust loads during glacial stages. Analogous to the Late Cenozoic, the Late Paleozoic was also an icehouse, and preliminary data suggest it was similarly characterized by high atmospheric dust loads. We are testing the hypothesis that detrital flux (a proxy for dust flux) varied systematically as a result of glacial-interglacial climate fluctuations during the late Paleozoic icehouse, and that these shifts might have driven variations in productivity.

We analyzed core samples collected at regular 1 m intervals through several Upper Pennsylvanian (Virgilian) glacioeustatic sequences within carbonates of the Horseshoe atoll (Midland basin), a phylloid-algal buildup that formed isolated from fluvio-deltaic terrigenous influx. Preliminary results demonstrate increases in the detrital fraction proximal to sequence boundaries (lowstand), and a crude upwardly coarsening (10-30 micron) trend within each sequence (15 to 30 m). Increased detrital material near sequence boundaries probably records enhanced aridity and windiness, and/or increased proximity and/or area of exposed land, during glacial times; the upwardly coarsening patterns within the sequences might reflect increased wind strength or source proximity. Studies are in progress employing additional approaches and tighter sampling to thoroughly assess these preliminary conclusions, and to examine any higher resolution (< 10⁵yrs) fluctuations in detrital flux and related productivity during this time.