Stable isotopes in late Pennsylvanian brachiopods from the United States: implications for Carboniferous paleoceanography

Stable isotopic analyses have been performed on nearly 500 nonluminescent brachiopod shells from Kansas, New Mexico, and Texas to evaluate temporal and geographic variability in the carbon and oxygen isotopic record for Late Pennsylvanian time. Regional variations are observed in the δ ¹⁸ O and δ ¹³ C values of nonluminescent brachiopod shells of the same genera. Data for nonluminescent brachiopods and marine cements reveal a mid-Carboniferous δ ¹³ C increase of 2‰ in Paleotethyan sea water. This increase is not seen in samples from the North American epicontinental seas, which opened to the Panthalassa ocean. This regional difference in δ ¹³ C appears to be due to changes in ocean circulation associated with the closing of the equatorial seaway and formation of Pangea. -from Authors