2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 1
Presentation Time: 10:00 AM


TIERNEY, Kate E., Department of Geological Sciences, The Ohio State University, 275 Mendenhall Labs, 125 South Oval Mall, Columbus, OH 43210 and SALTZMAN, Matthew R., Department of Geological Sciences, The Ohio State Univ, 275 Mendenhall Laboratory, 125 South Oval Mall, Columbus, OH 43210, tierney@geology.ohio-state.edu

Carbon isotope data were collected from 72 meters of Atokan age limestones in Arrow Canyon, Nevada. Samples were collected every 30 cm through cyclic carbonates that contained major and minor cycles. These data clearly show a periodicity close to the 400,000 year periodicity of the major coal units of the same age in the Appalachian Basin. The isotopic signal reflects the sequestration of organic matter as coal with highest values (~+4‰) occurring in lithologies indicative of deepest water, the same time coals were being deposited. Lowest δ13C values (~0‰) occur in silty limestone interpreted to be wind driven silt that accumulated during glacial maxima. These data show the impact coal deposition had on the function of the carbon cycle and may speak to the anomalously low CO2 levels that have been modeled for the Pennsylvanian. These data also show how the function of the carbon cycle was altered by the presence of coal swamps. When compared to Cenozoic data the contrast is distinct. Modern ocean circulation dictates that glacial episodes have higher δ13C values associated with maximum ice, more vigorous upwelling and increased nutrient delivery. Interglacial episodes show the decrease in circulation and nutrient delivery as lower δ13C values. We attribute the difference between the Pennsylvanian example and the Cenozoic example to the inundation of the continents and a change in the rate of terrestrial sequestration.