A Chemostratigraphic Study of Regional and Global Controls on Deposition and Preservation of Late Cambrian Shales and Carbonates of the Conasauga Group, Appalachian Basin, Usa
Year: 2017
Type: article
Abstract: This study reports data from the Late Cambrian Conasauga Group and overlying Copper Ridge Formation of the Central Appalachian region, eastern U.S.A. Geochemical, macro-, and micro-scale analysis of core material from southeastern Ohio was carried out to constrain the extent of oceanic anoxia and to characterize sediment fluxes on the carbonate platform and continental shelf of Laurentia contemporaneous with the Steptoean Positive Carbon Isotope Excursion (SPICE), a Late Cambrian global marine anoxic event. Carbonate sediments (primarily dolomite) record a positive δ13Ccarb excursion starting in the middle Nolichucky Formation, reaching its peak (+4.3) at the boundary between the Maynardville and Copper Ridge Formations. Strontium isotope ratios in the dolomitic units are only slightly offset from the expected Cambrian seawater values, suggesting minimal post-diagenetic disturbance of isotopic and trace element systematics. Elemental ratios within the lower Nolichucky Shale facies, including Th/U, FeT/Al, and Ce/Ce* anomalies, suggest an anoxic water column contemporaneous with the start of the δ13Ccarb excursion. Selective leaching of carbonate sediments reveal trends in redox-sensitive trace metals (e.g., U, Ni, V) indicative of regional and global marine anoxia during the peak of the Late Cambrian SPICE event.
Author: Justin Mackey
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2753345271