Geology & Geography Faculty Work
Title
Iron-Sulfide Concretions of the Ohio Shale: Glimpses of Deep Subseafloor Microbial Ecosystems of the Late Devonian
Document Type
Poster
Publication Date
2012
Publication Title
Geological Society of America North-Central Section, Abstracts with Programs
Volume Number
44
Issue Number
5
Abstract
Recent interest in black Devonian shales for natural gas exploitation has brought shale research into new importance. At the same time, advances in the understanding of deep subseafloor microbial ecosystems have revealed that microbes play a more pivotal role in geologic processes than ever imagined. The convergence of these two areas provides an excellent opportunity to reexamine enigmatic concretions of the Ohio Shale. The Huron member of the Ohio Shale is distinguished by the presence of carbonate concretions. These concretions vary considerably in size and differ in composition from the host rock. Their origins have been questioned since they were first described in 1873. Current models attribute concretion formation to abiotic mineral replacement of organic substances. However, smaller, iron-sulfide concretions inhabit the same horizons and are less well studied. Iron-sulfide mineralization has been attributed to biotic processes and may be connected to the presence of the larger carbonate concretions. Iron-sulfide concretions have been collected from three sites in Delaware and Franklin Counties in Ohio. These samples were investigated using reflected light microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Based on morphology, composition and size, the iron-sulfide concretions have been categorized into four different stages of paragenesis. These stages correlate well with known microbial zonations of deep subseafloor environments. Understanding the microbiological processes at work in the creation of black Devonian shales may shed light on how to exploit modern microbial systems to develop sustainable sources for carbon fuels in the future.
First Page
74
Recommended Citation
Fryer, Karen H. and Mumper, Eric, "Iron-Sulfide Concretions of the Ohio Shale: Glimpses of Deep Subseafloor Microbial Ecosystems of the Late Devonian" (2012). Geology & Geography Faculty Work. 27.
https://digitalcommons.owu.edu/geol_geog_pubs/27
Comments
Presented at the Geological Society of America Annual Meeting, Dayton, OH