Mechanisms of PETM global change constrained by a new record from central Utah

Catastrophic carbon release and global warming during the Paleocene-Eocene thermal maximum (PETM) profoundly affected continental climate and ecosystems. Understanding of the details and mechanisms of these effects is limited by the poor geographic coverage of existing continental PETM records. Here, we extend the record of this event in North America through identification of the PETM carbon isotope excursion within a sequence of paleosols in the North Horn Formation of central Utah, some 500 km to the south of previous records from northern Wyoming. Data from the new site suggest that patterns of climatological change were similar across a meridional transect of western North America but that PETM climate was relatively more and in the southern Rocky Mountains, possibly reflecting diversion of precipitation from middle to high latitudes. Our results are consistent with two proposed mechanisms explaining variation in the amplitude of continental PETM carbon isotope records in terms of changes in floral composition or varying environmental wetness, and they present opportunities for future tests of proposed north-south biotic dispersal during the PETM.