To evaluate the isotopic record of climate change and carbon sequestration in the Late Paleozoic, we have compiled new and published oxygen and carbon isotopic measurements of more than 2000 brachiopod shells from Carboniferous through Middle Permian (359-260 Ma) strata worldwide. We focus on the isotopic records from the U.S. Midcontinent and the Russian Platform because these two regions provide well-preserved marine fossils spanning a broad time interval.
Brachiopod shells were processed and screened for diagenesis by different methods depending on the research group. Some groups crush shells and pick clear crystals under the microscope. Five to ten milligrams of Ca carbonate are analyzed for trace and minor elements (Mg, Sr, Fe, Mn). Other research groups thin-section shells and use cathodoluminscence and plane light microscopy to screen for diagenesis. Nonluminescent shell is microsampled (0.05-0.1 mg) on the thin-section or complementary billet. All research groups use isotope ratio mass spectrometer for carbon (13C/12C) and oxygen (18O/16O) analyses. These data are used to examine paleotemperatures and their relation to climate in the past.
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