Terrestrial Carbon Sequestration in Devonian-Mississippian Anoxic Basins

The black shales of the Appalachian Devonian Basin (ADB) provide a unique opportunity to assess mechanisms that influenced water-column conditions, productivity, and sedimentation in what may have been (at times) a regionally extensive anoxic basin. While anoxic bottom-water conditions may have influenced organic carbon accumulation, growing evidence suggests that other factors contributed significantly to the degree and style of biogeochemical cycling within the water column and to the patterns of sedimentation. Algeo and co-workers (1995, 2001) have proposed that Late Devonian-Early Mississippian time was a pivotal episode in Earth history, during which the enhanced influx of continentally derived nutrients may have triggered reducing conditions in the marine environment and, thereby, contributed to carbon sequestration. Not only did this event lead to higher levels of productivity within the marine environment, but it also provided an enhanced flux of organic matter to the basin, that of refractory terrestrial matter associated with the evolution of higher plants. By integrating petrographic, geochemical, and sedimentological proxies, PIs will reconstruct Late Devonian-Early Mississippian conditions within the ADB. The proposed research will test the hypothesis that the advent of terrestrial higher plants played a commanding role in altering the mode of organic carbon accumulation in a spatially extensive, anoxic marine setting. The significant, and perhaps unique, contribution PIs hope to make is to document a marine record of this terrestrial colonization using organic petrography and organic geochemistry, and demonstrate that an increased influx of terrestrial organic matter across the ADB, particularly oxidized material that may have formed during wildfires, may have been a more important factor in the accumulation of organic-rich sediments during that time in Earth history than previously realized.