PERMIAN PALEOTEMPERATURES RECORDED IN MID-PALEOLATITUDE AND PALEOEQUATORIAL HALITE DEPOSITS

Paleoclimate reconstruction of the Late Paleozoic deglaciation, the transition from icehouse to greenhouse climate states during the Permian, provides key insights into current climate change. In this study, we use the homogenization temperature of artificially nucleated vapor bubbles in primary, unaltered fluid inclusions from crystals in bedded halite to determine the temperature of the parent brine during the precipitation of mid-paleolatitude Permian halite from Ukraine (Asselian), Russia (Kungurian), and Poland (Wuchiapingian). Detailed petrographic study of halite samples identified numerous features indicative of precipitation in shallow water, including primary dissolution and desiccation features; this suggests that these homogenization temperatures may be a good proxy for air temperature. For context, we also compiled previously published homogenization temperatures of artificially nucleated vapor bubbles in primary, unaltered fluid inclusions in paleoequatorial Permian halite from Kansas (Kungurian) and Texas (Wuchiapingian). A high-resolution comparison between paleoequatorial and mid-paleolatitude settings is hindered by uncertainty as to the exact position of samples within Permian stages as well as differences in the temporal distribution of sampled halite. In general, homogenization temperatures obtained from mid-paleolatitude halite (~15 to ~25°C, on average) are lower than those from paleoequatorial halite (~25 to ~40°C, on average). At mid-paleolatitudes, homogenization temperatures are relatively stable through the Permian. In contrast, homogenization temperatures from paleoequatorial samples typically have a greater range and are highest during the Kungurian (to ~70°C). Our mid-paleolatitude samples do not show the extreme Kungurian warming reconstructed for paleoequatorial settings. Homogenization temperatures appear to be most similar across paleolatitude during the Wuchiapingian. The Late Paleozoic deglaciation appears to have resulted in more variability in paleoequatorial temperature conditions than at mid-paleolatitudes.