CONTROLS ON ORGANIC CARBON ACCUMULATION IN THE LATE DEVONIAN NEW ALBANY SHALE, WEST-CENTRAL KENTUCKY, ILLINOIS BASIN

Author

Seare G. Ocubalidet, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2013

Degree Name

Master of Science

Department

Geology

First Advisor

Rimmer, Sue

Abstract

The Late Devonian-Early Mississippian-age New Albany Shale is both a source rock and reservoir rock for hydrocarbons in the Illinois Basin. Previously suggested models for organic carbon enrichment consider productivity, anoxia, and the interdependent roles of sedimentation, primary production, and microbial metabolism. This study attempts to reconstruct paleoenvironmental conditions during deposition and re-evaluates these models using geochemical data from multiple cores across the eastern edge of the Illinois Basin in west-central Kentucky. Geochemical methods utilizing redox-sensitive major elements (C, S, Fe, P, K, Ti, and Si), trace elements (V and Mo), and ratios (Ni/Co, V/Cr, and V/(V+Ni) are used. Analysis of paleo-redox indicators suggests variable bottom-water conditions during accumulation of the New Albany Shale members including: anoxic to possibly euxinic conditions for the Clegg Creek Member, anoxic to periodically dysoxic conditions for the Camp Run, and dysoxic to oxic (normal marine) for the Morgan Trail and Blocher Members. Variability in redox proxy results suggests that multiple parameters should be utilized in such studies rather than relying on a single proxy. High C/P ratios observed in these members may be controlled by regeneration of P, enhanced productivity, and sequestration of organic carbon (the productivity-anoxia feedback (PAF) mechanism) under anoxic conditions. The lack of correlation between organic carbon content and clastic-influx proxies suggests that organic matter (OM) accumulation was not controlled by sedimentation rate or increased nutrient supply associated with increased sediment influx.