REGIONAL-SCALE FAUNAL CHANGES DURING EARLY PERMIAN CLIMATE FLUCTUATIONS

The geographic distribution of a marine invertebrate taxon is influenced by its temperature tolerance and dispersal capability. As a result, paleobiogeographic patterns can provide an estimate of relative paleotemperature and ocean circulation patterns to help constrain climate model results, analogous to but potentially more sensitive than climate-sensitive sediments. I used a database containing occurrences of more than 2750 marine invertebrate genera at 12,000 Permian fossil localities to produce quantitative estimates of the climatic affinity of the marine fauna. For each genus, the mean paleolatitude of its occurrences was calculated to provide an estimate of its temperature sensitivity; the paleoclimate of a 1 degree by 1 degree bin was then estimated from the mean temperature sensitivity value of all genera occurring that bin. The overall pattern closely matches previous paleobiogeographic reconstructions and is able to quantify trends previously recognized from qualitative approaches, such as the progressive cooling of Boreal regions from the Sakmarian to Wordian. More subtle regional changes can also be reconstructed. Northern hemisphere faunas from eastern Panthalassa have a cooler climate affinity than faunas from similar paleolatitudes on the western margin, consistent with the expected influence of cool and warm boundary currents. Temporal trends in western Laurentian faunas further indicate intensification or cooling of the southerly-flowing boundary current in the Middle Permian. Similar faunal changes and climatic boundaries can be identified in the Cimmerian continents in Tethys and in eastern Australia, placing constraints on paleotemperature changes and the location and intensity of ocean currents during major Permian climate fluctuations.