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Stable isotopic response to late Eocene extraterrestrial impacts

By
Aimee E Pusz
Aimee E Pusz
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA
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Kenneth G Miller
Kenneth G Miller
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA
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James D Wright
James D Wright
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA
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Miriam E Katz
Miriam E Katz
Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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Benjamin S Cramer
Benjamin S Cramer
Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA
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Dennis V Kent
Dennis V Kent
Department of Earth and Planetary Sciences, Rutgers University, Piscataway, New Jersey 08854, USA, and Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
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Published:
April 01, 2009

We evaluated the age of two Upper Eocene impact ejecta layers (North American microtektites linked to the Chesapeake Bay impact structure and clinopyroxene [cpx] spherules from the Popigai crater) and the global effects of the associated impact events. The reported occurrence of cpx spherules from the Popigai impact structure at South Atlantic ODP Site 1090 within the middle of magnetochron C16n.1n yields a magnetochronologic age of 35.4 Ma. We generated high-resolution stable isotope records at Sites 1090, 612 (New Jersey slope), and Caribbean core RC9-58 that show: (1) a 0.5‰ δ13C decrease in bulk-carbonate at Site 1090 coincident with the Popigai cpx spherule layer, and (2) a 0.4‰–0.5‰ decrease in deep-water benthic foraminiferal δ13C values across the Popigai impact ejecta layer at Site 612 and core RC9-58. We conclude that the δ13C excursion associated with Popigai was a global event throughout the marine realm that can be correlated to magnetochron C16n.1n. The amplitude of this excursion (~0.5‰) is within the limits of natural variability, suggesting it was caused by a decrease in carbon export productivity, potentially triggered by the impact event(s). North American microtektites associated with the Chesapeake Bay impact occur stratigraphically above the Popigai cpx spherules at Site 612 and core RC9-58. We found no definite evidence of a δ13C anomaly associated with the North American microtektite layer, though further studies are warranted. High-resolution bulk-carbonate and benthic foraminiferal δ18O records show no global temperature change associated with the cpx spherule or North American microtektite layers.

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Contents

GSA Special Papers

The Late Eocene Earth—Hothouse, Icehouse, and Impacts

Christian Koeberl
Christian Koeberl
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Alessandro Montanari
Alessandro Montanari
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Geological Society of America
Volume
452
ISBN print:
9780813724522
Publication date:
April 01, 2009

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