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December 10, 2018


Pinnacle reef tracts are geomorphic features of carbonate systems that originated in the early Silurian and display an episodic distribution into the Cenozoic. Detailed study of Silurian pinnacle reefs of the United States midcontinent demonstrates repeated motifs, but most enigmatic is the coincidence of carbonate carbon isotope (δ13Ccarb) excursions and reef pulses. Silurian δ13Ccarb excursions were associated with environmental changes and extinctions, and reefs appear to mark a resurgence of conditions favorable to biomineralizers following those extinction events. Previous workers in the region identified six discrete reef origination events in the United States midcontinent during the Silurian. Our reevaluation of outcrops and cores, conodont collections, and the generation of considerable new chemostratigraphic data across the region are clarifying the age relations of these events and their relationships to perturbations of the global carbon cycle.

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GSA Special Papers

Ancient Oceans, Orogenic Uplifts, and Glacial Ice: Geologic Crossroads in America’s Heartland

Lee J. Florea
Lee J. Florea
Indiana Geological and Water Survey Indiana University 611 N. Walnut Grove Avenue Bloomington, Indiana 47405, USA
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Geological Society of America
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December 10, 2018




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