Gas-Bearing Ohio Shale along Lake Erie--Stratigraphy, Petrology, and Sedimentology: ABSTRACT

Abstract

Increased interest in low-yield gas-bearing strata has led to reexamination of the Ohio Shale in the vicinity of Lake Erie where it has had a history of marginal commercial production for over a century. These strata thin depositionally westward from a maximum of 2,000 ft (600 m) at the Pennsylvania border to less than 600 ft (180 m) near Sandusky where they are truncated by erosion on the Findlay arch. Common lithotopes are black and gray shale, siltstones, and rare carbonate rocks. Black shales are most abundant in the west where gray shales and siltstones are rare. In the east, gray shales and siltstones constitute 75% of the section and the remainder is mainly black shale and minor carbonate rocks. Thin-section petrology revealed that the black shale commonly contains, by volume, less than 20% silt-size quartz and feldspar, 30 to 60% clay and mica, and 15 to 35% organic material. Gray shale commonly contains less than 30% silt-size quartz and feldspar, 50 to 90% clay and mica, and less than 10% organic material. Much of the silt is concentrated in discrete laminae a few grains thick. Production records are related to facies distribution to provide an exploration tool. Cross sections and paleocurrents indicate that the Upper Devonian prodeltaic muds and turbidite siltstones were deposited episodically in a euxinic basin. End_of_Article - Last_Page 1576------------