Core Reflectance Spectroscopy and Well Logging of the Point Pleasant/Utica Sub-basin, Ohio

Abstract

The Ordovician Point Pleasant Formation and Utica Shale are calcareous shales interbedded with limestone that extend throughout Ohio, and lie on top of the Trenton and Lexington carbonate ramps. These shales have previously been linked to the Sebree Trough, a bathymetric low where carbonate production ceased and silicliclastics were deposited in a deep, anoxic sea. To analyze the change in environments, well logs were used to analyze the thickness, structure and contact between the Point Pleasant and the carbonate ramps, and reflectance spectroscopy on rock core was used to observe high spatial resolution changes in mineralogy with depth in order to determine changes in the environment during deposition. Well logs and rock core indicate an abrupt change between the Point Pleasant and Trenton on the northwestern edge of the basin, while the contact with the Lexington on the southeastern edge of the sub-basin is a gradation (interbedded?) contact and consists of more frequent limestone beds within the shale. Mineralogy and core descriptions confirm these contacts between the formations, with a gradational change in mineralogy from more shale to more carbonate on the southeastern edge (Point Pleasant and Lexington), and an abrupt change from shale to carbonate within the basin (Point Pleasant and Trenton). This suggests two different mechanisms affecting the two contacts between the Point Pleasant and the underlying carbonate platform.

AAPG Datapages/Search and Discovery Article #90258 © 2016 AAPG Eastern Section Meeting, Lexington, Kentucky, September 25-27, 2016