Image: Pyrite concretion (Chattanooga Shale, Upper Devonian; Burkesville West Rt. 90 roadcut, Kentucky, USA) 1 (42300453012)

Description: Pyrite concretion in the Devonian of Kentucky, USA. Concretions are post-depositional structures found in some sedimentary successions, particularly in shales. They vary in mineralogy, size, and shape, but often have slightly flattened spheroidal shapes. They typically form by post-depositional mineralization around some nucleus (a rock fragment or fossil fragment). This concretion is composed of iron sulfide (FeS2) - pyrite and/or marcasite. The concretion's host rock is the Chattanooga Shale, which consists of dark-colored, chippy-weathering, marine mudshales of Late Devonian age. These black shales were deposited in a moderately deep, anoxic seafloor environment. This was a widespread lithofacies during the Late Devonian's Global Anoxia Event. The Chattanooga Shale is equivalent to the Ohio Shale, the Antrim Shale, and the New Albany Shale in surrounding states. Stratigraphy: Chattanooga Shale, Upper Devonian Locality: roadcut on the northern side of Route 90, just west of Burkesville, central Cumberland County, southern Kentucky, USA (36° 47’ 51.17” North latitude, 85° 23’ 10.62” West longitude)
Title: Pyrite concretion (Chattanooga Shale, Upper Devonian; Burkesville West Rt. 90 roadcut, Kentucky, USA) 1 (42300453012)
Credit: Pyrite concretion (Chattanooga Shale, Upper Devonian; Burkesville West Rt. 90 roadcut, Kentucky, USA) 1
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
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