Oxygen and hydrogen isotope compositions of Permian pedogenic phyllosilicates: Development of modern surface domain arrays and implications for paleotemperature reconstructions

The δD values of the phyllosilicates range from − 69‰ to − 55‰. The δ18O values range from 19.5‰ to 22.7‰. If these samples preserve a record of equilibrium with paleo-meteoric waters, the isotopic compositions of the phyllosilicates correspond to paleotemperatures of phyllosilicate crystallization ranging from 22 ± 3 °C to 35 ± 3 °C. In particular, the stratigraphic trend of calculated temperatures from Midland basin samples suggests that Early Permian surface temperatures may have been up to 10 °C warmer than those of the latest Pennsylvanian.