Molecular Controls of Mobilization of Ancient Organic Compounds from Devonian Black Shales

Abstract

Organic-rich black shales are exposed and weathered widely across the Appalachian Basin. The weathering can remove organic matter, influencing regional carbon cycles and biogeochemistry of adjacent water bodies. Furthermore, the weathering may significantly alter the concentrations and compositions of some organic compounds, which are often used to reconstruct paleoenvironments. As such, understanding the effects of weathering on organic compounds in black shales is important for constraining the role of black shales in regional environmental and ecosystem processes, as well as for evaluating the reliability of paleoenvironmental reconstruction. To date, no study has been performed to understand this process in the molecule level. I propose to analyze changes in organic compounds due to weathering from two outcrops of the Late Devonian black shales undergoing different degrees of weathering. Samples will be collected via horizontal drilling from the surface to a depth where weathering influences are minimal. I will apply the Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICRMS) and nuclear magnetic resonance spectroscopy (NMR) on chemically extracted organic matter to assess the molecule-level changes in organic compounds as a function of weathering. This study will reveal fundamental biogeochemical mechanisms regulating ancient organic C and S compounds those are mobilized into the active, contemporary biogeochemical cycles. Moreover, my results will provide molecular-level information about the ancient organic compounds being mobilized to waterways and influencing local aquatic chemistry and environment. Lastly, the study can evaluate the reliability of geochemical proxies applied to chemostratigraphic studies for paleoenvironments.

AAPG Datapages/Search and Discovery Article #90351 © 2019 AAPG Foundation 2019 Grants-in-Aid Projects