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Evaluating the Geochemical Consequences of Aragonite-to-Aragonite Diagenesis in Freshwater Fossil Bivalves

Snell, Kathryn E. and Eiler, John M. and Dettman, David L. and Grotzinger, John P. and Koch, Paul L. (2012) Evaluating the Geochemical Consequences of Aragonite-to-Aragonite Diagenesis in Freshwater Fossil Bivalves. In: 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, CA.

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Carbonate clumped isotope (Δ_(47)) thermometry provides an independent test of the metrics used to assess the preservation of carbonate rocks and fossils. Additionally, Δ_(47) thermometry, when combined with other geochemical and structural measurements, may establish whether diagenesis occurred under closed-system conditions, open-system conditions, or some combination thereof. Here we present an example of diagenesis of Eocene-aged freshwater mollusk fossils (Unionidae) from Wyoming. The fossils yielded Δ_(47) temperatures from 41-46°C, which is physiologically unreasonable. However, X-Ray diffraction (XRD) data indicate that all but one of the fossils contain only aragonite — the carbonate phase unionids deposit; one sample contained small amounts of calcite in powder XRD analysis. We used scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), cathodoluminescence (CL) and secondary electron mass spectrometry (SIMS) of polished thin sections and etched fragments to describe the detailed textural, mineralogical, and trace element characteristics of two of these fossils and one modern unionid shell.

Item Type:Conference or Workshop Item (Paper)
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Grotzinger, John P.0000-0001-9324-1257
Additional Information:© 2012 AAPG. AAPG Search and Discovery Article #90142.
Record Number:CaltechAUTHORS:20130814-153842490
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39921
Deposited By: Tony Diaz
Deposited On:16 Aug 2013 21:25
Last Modified:03 Oct 2019 05:12

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