A major drop in seawater 87Sr/86Sr during the Middle Ordovician (Darriwilian): Links to volcanism and climate?
- 1Department of Geological Sciences, Indiana University, 1001 E 10th Street, Bloomington, Indiana 47405, USA
- 2School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory, 125 S. Oval Mall, Columbus, Ohio 43210, USA
- 3Department of Geosciences and Astrobiology Research Center, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- *E-mail: seayoung{at}indiana.edu.
Abstract
A large drop in seawater 87Sr/86Sr during the Middle Ordovician was among the most rapid in the entire Phanerozoic. New 87Sr/86Sr measurements from Nevada indicate that the rapid shift began in the Pygodus serra conodont zone of the upper Darriwilian Stage. We use a numerical model to explore the hypothesis that volcanic weathering provided the flux of nonradiogenic Sr to the oceans. A close balance between volcanic outgassing and CO2 consumption from weathering produced steady pCO2 levels and climate through the middle Katian, consistent with recent Ordovician paleotemperature estimates. In the late Katian, outgassing was reduced while volcanic weathering continued, and resulted in a cooling episode leading into the well-known end-Ordovician glaciation.
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- Received 17 February 2009.
- Revision received 27 May 2009.
- Accepted 2 June 2009.
- © 2009 Geological Society of America
