Late Pennsylvanian seasonality reflected in the <sup>18</sup> O and elemental composition of a brachiopod shell

To evaluate the potential for the study of Late Pennsylvanian seasonality, detailed isotopic and elemental analyses were performed on a single specimen of the brachiopod Neospirifer dunbari. Contours of 18 O, Mg, Na, and S concentrations parallel growth bands and reveal a record of 1 1/2 to 2 cycles. Mg, S, and Na contents varied inversely with 18 O. This trend is opposite to the expected diagenetic trend and is consistent with the temperature dependences of Mg content and 18 O, thus implying preservation of shell chemistry. The ~1.2 range in 18 O values suggests a seasonal temperature variation of 5 to 6C. This high seasonality for the tropical epicontinental sea of Kansas supports climate-model predictions of enhanced continentality in Pangean climate. -Authors

Late Pennsylvanian seasonality reflected in the ¹⁸ O and elemental composition of a brachiopod shell Academic Article