CLIMATIC AND HYDROLOGIC CHANGE DURING THE EOCENE-OLIGOCENE TRANSITION IN THE NORTH AMERICAN INTERIOR
We present paired leaf wax biomarker and clay hydrogen isotope data from the WRG to produce a new record of hydrological change and/or ecosystem shifts through the EOT. Clay δD data show a negative shift of <15 ‰ from the late Eocene through early Oligocene, while leaf wax n-alkanes record a negative shift in excess of 50 ‰ with a synchronous positive change in average chain length. We infer an increase in aridity from these data, with a potential associated shift from coniferous/evergreen forests to more savannah-style vegetation as the climate became drier throughout the transition into the Oligocene. These data provide new constraints on the impact of the EOT in North America, and highlight the potential role of increasing aridity, in addition to declining temperatures, in shaping terrestrial ecosystems during this interval.