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Distal signatures of Late Ordovician oceanic anoxia; new data from a classic epeiric ramp transect

Patrick I. McLaughlin, Norlene Emerson, Brian Witzke, Bryan Sell and Poul Emsbo
Distal signatures of Late Ordovician oceanic anoxia; new data from a classic epeiric ramp transect (in Archean to Anthropocene; field guides to the geology of the Mid-Continent of North America, James D. Miller (editor), George J. Hudak (editor), Chad Wittkop (editor) and Patrick I. McLauglin (editor))
Field Guide (Geological Society of America) (September 2011) 24: 259-284

Abstract

New data and review of classic sections from the Middle and Upper Ordovician North American Midcontinent in the Upper Mississippi Valley provide a refined picture of the age, stable isotope geochemistry, faunal composition, and--ultimately--origin of this epeiric ramp succession. Sequence stratigraphic analysis reveals a series of unconformity-bounded, genetically related facies packages. Shallowing and deepening trends are sometimes difficult to resolve due to a paucity of hydrodynamic indicators, yet unconformity surfaces are well marked by hardgrounds and confirmed by negative C-isotope spikes. Recent conodont biostratigraphy, new U-Pb radioisotopic ages for K-bentonites, and correlation of C-isotope profiles to global trends suggest that the succession spans the Darriwilian to Hirnantian epochs. Focus on Platteville to lower Galena Group strata (Sandbian to early Katian) provides a temporally high-resolution look at the onset and evolution of a long-term (>2 m.y.) positive carbon-isotope excursion, short-term perturbations in that record, and relationship to the preservation and diversity of the enclosed fauna and strata. Major changes in authigenic mineral suites and organic carbon content throughout the Upper Ordovician Upper Mississippi Valley suggest at least three major redox cycles. The combined evidence for globally recognized, positive carbon-isotope excursions coincident with these redox cycles, as well as high-frequency, sea-level fluctuations and successive faunal turnover events, suggests far-field responses to multiple global oceanic anoxic events.


ISSN: 2333-0937
EISSN: 2333-0945
Serial Title: Field Guide (Geological Society of America)
Serial Volume: 24
Title: Distal signatures of Late Ordovician oceanic anoxia; new data from a classic epeiric ramp transect
Title: Archean to Anthropocene; field guides to the geology of the Mid-Continent of North America
Author(s): McLaughlin, Patrick I.Emerson, NorleneWitzke, BrianSell, BryanEmsbo, Poul
Author(s): Miller, James D.editor
Author(s): Hudak, George J.editor
Author(s): Wittkop, Chadeditor
Author(s): McLauglin, Patrick I.editor
Affiliation: Wisconsin Geological and Natural History Survey, Madison, WI, United States
Affiliation: University of Minnesota-Duluth, Department of Geological Sciences, Duluth, MN, United States
Pages: 259-284
Published: 201109
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 39
Accession Number: 2012-009902
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. col., sketch map
N43°30'00" - N49°00'00", W97°10'00" - W89°45'00"
N42°30'00" - N47°00'00", W92°49'60" - W86°45'00"
N40°25'00" - N43°30'00", W96°34'60" - W90°10'00"
Secondary Affiliation: Natural Resources Research Institute, USA, United StatesMinnesota State University, USA, United StatesWisconsin Geological and Natural History Survey, USA, United StatesUniversity of Wisconsin-Richland, USA, United StatesUniversity of Iowa, USA, United StatesUniversity of Geneva, CHE, SwitzerlandU. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201205
Program Name: USGSOPNon-USGS publications with USGS authors
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