MULTI-PROXY TERRESTRIAL PALEOCLIMATE RECONSTRUCTION OF THE EOCENE-OLIGOCENE TRANSITION IN EUROPE AND NORTH AMERICA

The Eocene-Oligocene transition (EOT; ~33.9 Ma ago) represents a major climatic cooling event triggered by falling atmospheric pCO₂ that was accompanied by Antarctic glaciations. Here, multi-proxy paleoclimatic records (mean annual temperature, mean annual precipitation) records derived from isotopic and elemental geochemistry of paleosols and fossil snails preserved in Oregon, Montana, Nebraska, England, and Spain are used to explore spatial patterns of climatic change during the EOT. At all of the sites, chemical weathering declined across the EOT, consistent with falling atmospheric pCO₂. Cooling was not uniform, with larger magnitude changes at higher paleolatitude sites (England) than at lower paleolatitude sites, a pattern that matches marine paleotemperature proxies. Among terrestrial EOT records, the degree of continentality was also important, with intermontane, endorheic basins generally recording more muted changes relative to near-coastal records or exorheic basins. Paleoprecipitation records also show substantial spatial heterogeneity, with increased aridity in Nebraska and Oregon, relatively stable precipitation in Montana and Spain, and wetter conditions in England. These climatic records also provide environmental context for paleobotanical records from the same sites, making it possible to consider the degree and drivers of floral changes.