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of Organic Matter in the Rome Trough
of the Appalachian Basin
and Its Subsequent Thermal History1
John B. Curtis2 and
We used geochemical data to examine the origin
and preservation of organic matter contained in the lower part of the Huron
Member of the Ohio Shale formation and the Rhinestreet Shale Member of
the West Falls Formation (Devonian) in Kentucky, Ohio, West Virginia, and
Virginia. The thermal history of the organic matter was determined by relating
relative temperatures experienced by the organic matter to the geologic
The organic matter in these formations is
predominantly marine in origin and was most probably derived largely from
algal organisms. Although the rate of production of marine organic matter
may have been uniform within the basin, its preservation apparently was
controlled by the existence of a set of fault-bounded anoxic subbasins
associated with the Rome trough, a Cambrian structural complex. These subbasins
apparently were anoxic because they limited oxygen recharge by circulating
waters. Preservation of organic matter was also enhanced by periodic blooms
of the alga Tasmanites
and similar organisms in the waters above the subbasins during both early
Huron and Rhinestreet deposition.
A significant negative correlation was identified
between the vitrinite reflectance peak temperature, an integrated measure
of the thermal history of a rock, and the hydrogen index, a measure of
the remaining hydrocarbon-generation potential of kerogen. Although peak
temperatures were controlled by burial depth, excess heating occurred
1997. The American Association of Petroleum Geologists. All rights reserved.
received October 25, 1995; revised manuscript received June 7, 1996; final
acceptance October 28, 1996.
of Geology and Geological Engineering, Colorado School of Mines, Golden,
of Geological Sciences, Ohio State University, Columbus, Ohio 43210.
for sample collection and analysis was provided by the Gas Research Institute,
whose contribution is gratefully acknowledged. We thank M. D. Lewan and
C. E. Barker for their guidance and reviews of earlier drafts of this manuscript.
We also appreciate the critical reviews of G. Demaison, R. Kepferle, and
C. Laughrey. Contribution No. 019 of the Colorado School of Mines Geochemistry
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