Image: Fossiliferous chert (Upper Mercer Flint, Middle Pennsylvanian; Nellie West Outcrop, Coshocton County, Ohio, USA) 5 (31110222613)

Description: Fossiliferous chert from the Pennsylvanian of Ohio, USA. "Flint" is the official gemstone of Ohio. Flint is actually chert (the two terms are synonymous, despite what anyone else might say), a cryptocrystalline, quartzose sedimentary rock. High-quality, colorful, multicolored, and multipatterned flint is moderately common at some Ohio localities. A couple famous flint occurrences in east-central Ohio include the Vanport Flint at Flint Ridge and Nellie Blue Flint in Coshocton County. The rock shown above is weathered chert from the Upper Mercer Flint, a somewhat persistent horizon of chertified marine fossiliferous limestone in east-central and eastern Ohio called the Upper Mercer Limestone. The Upper Mercer is usually a black flint with whitish speckles (= often body fossils and fossil fragments). This sample is quite fossiliferous. The prominent, gray-colored fossil is a brachiopod shell. Brachiopods are sessile, benthic, filter-feeding lophophorates with two shells. They first appear as fossils in the Cambrian and were abundant on many shallow seafloors during the Paleozoic. They are scarce in modern oceans. Stratigraphy: Upper Mercer Flint (= chertified Upper Mercer Limestone), upper Bedford Cyclothem, upper Pottsville Group, Atokan Series, lower Middle Pennsylvanian Locality: Nellie West Outcrop, western Jefferson Township, western Coshocton County, east-central Ohio, USA
Title: Fossiliferous chert (Upper Mercer Flint, Middle Pennsylvanian; Nellie West Outcrop, Coshocton County, Ohio, USA) 5 (31110222613)
Credit: Fossiliferous chert (Upper Mercer Flint, Middle Pennsylvanian; Nellie West Outcrop, Coshocton County, Ohio, USA) 5
Author: James St. John
Usage Terms: Creative Commons Attribution 2.0
License: CC BY 2.0
License Link: https://creativecommons.org/licenses/by/2.0
Attribution Required?: Yes