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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 63 (1979)

Issue: 9. (September)

First Page: 1589

Last Page: 1589

Title: Petrology and Depositional Environments of Boyle Dolomite (Middle Devonian) in East-Central Kentucky: ABSTRACT

Author(s): J. Todd Stephenson, Wayne A. Pryor

Article Type: Meeting abstract


The Middle Devonian Boyle Dolomite is a sequence of dolomite, dolomitic limestone, limestone, chert, and shale which has been deposited on a regional unconformity that truncates successively older units toward the axis of the Cincinnati arch. The Boyle varies in thickness (0 to 11 m) and crops out in a 40-km-wide, northeast-trending, arcuate belt on the eastern margin of the Blue Grass region.

The Boyle Dolomite is divided into the following four lithofacies: Kiddville, Winston (Boyle limestone), Casey, and Duffin. The basal Kiddville is a quartzose dolomicstone with abundant fish remains and represents the slow accumulation of a lag deposit in a platform environment. The Winston (Boyle limestone) is a crinoidal grainstone-packstone and indicates a full marine transgression with high-energy winnowing action on the shelf. The Casey is a cherty dolomicstone with a sparse fauna and represents continued transgression of carbonate mud environments. The Duffin is an interbedded dolomicstone and shale with an abundant and diverse trace-fossil assemblage and marks the transition between carbonate and clastic deposition in Middle to Late Devonian time.

An upward decrease in fossil abundance, diversity, and detrital clastics corresponds to an increase in the percentage of dolomite. Iron substitution in the dolomite crystal lattice increases upward and suggests an influence of reducing diagenetic environments. Trace-fossil analysis reveals a shelf to slope assemblage in the Boyle.

The Boyle Dolomite represents the marine transgression in the western margin of the basin during Middle Devonian time. The transition between open-marine carbonate and anoxic black shale is a shelf to slope carbonate mud with a predominant infaunal assemblage.

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