Cleveland Shale, Geological formation in Ohio, United States.
Cleveland Shale is a sedimentary rock formation in Ohio, sandwiched between two other rock layers and made up of dark gray and black shale. Its thickness varies from place to place, and the rock contains organic material from which oil and gas can be extracted.
The formation was first described in 1870 during a geological survey of Ohio and has been studied ever since. Work on this rock unit helped scientists understand how sediment built up in the ancient Appalachian basin.
Cleveland Shale takes its name from the city of Cleveland in Ohio, where the formation is exposed at the surface in several places. Geology students and researchers visit these outcrops regularly to study the dark layered rock up close.
The formation is visible at road cuts and quarries across Ohio, where the dark rock is exposed at the surface and easy to spot. Anyone visiting an outcrop or an active site should wear sturdy footwear, as the ground can be uneven and the rock is hard and dense.
The lowest part of the formation contains thin bands of pyrite mixed with fossil fish bones, pointing to a shallow, low-oxygen sea that once covered this part of North America. These fish remains are among the oldest vertebrate fossils found in Ohio.
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