Paper No. 49-3
Presentation Time: 1:30 PM-5:30 PM
COMPARING LOCAL AND BASINAL PATTERNS OF MARINE BLACK SHALE GEOCHEMISTRY IN THE DEVONIAN APPALACHIAN BASIN, KENTUCKY
With the evolution of forests during the Mid to Late Devonian (~375mya), atmospheric composition and the Earth’s climate system were drastically altered and the carbon cycle disrupted. Previous studies have proposed that the newly evolved forests increased nutrient and organic material runoff to marine settings which led to eutrophication. These anoxic conditions resulted in increased black shale deposition, global-scale climate change, and related extinctions. In order to better understand this process, organic geochemical data has been collected from the two closely-spaced cores from the western Appalachian Basin, Powell and Estill Counties, Kentucky. This study is investigating whether the chemostratigraphic patterns observed in the two cores closely agree with one another (i.e., local pattern), and if the patterns observed in these two cores are similar to those observed in previous studies of correlative Northern Appalachian Basin black shale (i.e., basinal pattern). X-ray fluorescence and loss-on-ignition are used to determine elemental composition and organic matter content, respectively; this dataset provides a deeper understanding of lithology, the conditions present during deposition, and allows chemostratigraphic correlation. Organic carbon isotopic analysis will also be used to differentiate marine and terrestrial organic matter and therefore constrain organic matter fluxes into the depositional environment and reconstruct any changes in organic matter composition through time both locally and basinally. Both cores have a similar lithostratigraphic succession: the Boyle Formation is overlain by Portwood and Trousdale Members of the New Albany Shale. Also recognized in both cores is the upper, middle, and lower units of the Portwood Member. Correspondingly, preliminary x-ray fluorescence data for elemental proxies for lithology (Si, Al, and Ca) show similarities between the two cores. Preliminary elemental data also suggests that bottom-water paleoredox conditions were oxic to suboxic. Ultimately, the data from this study will contribute to a deeper understanding of Appalachian Basin depositional environments and also serve as a reference for understanding future anthropogenic disruptions to the carbon cycle.