COMPARING RIVERBED SEDIMENT CHANGES IN RESPONSE TO THE PALEOCENE-EOCENE THERMAL MAXIMUM EVENT, PYRENEES MOUNTAINS, SPAIN

The Paleocene-Eocene Thermal Maximum (PETM) event occurred 56MA, when the average global temperature increased between 5-9 degrees Celsius. With the increase in global temperature today (July 2023 broke temperature records around the globe), we can look at the PETM to determine what could happen if global temperatures continue to increase, including how landscapes may respond to rising temperatures and changing precipitation patterns. The Paleocene Esplugafreda and Eocene Claret formations exposed in the Pyrenees Mountains, Spain, provide an opportunity to evaluate how ancient rivers responded to the PETM climate change. Using field photos of ancient riverbed deposits from before, during, and after the PETM, I measured attributes of sediment from three study areas and determined paleo-river flow conditions before, during, and after the PETM. In each study area I traced sediment grains on >50 photographs to determine sizes, roundness, aspect ratio, solidity, and circularity of sediment before, during, and after the PETM and used this information to interpret paleoflow conditions throughout the study area. The preliminary results show that there was a significant amount of scatter and overlap for bed-sediment attributes in space and time. An increase in sorting and aspect ratio (more elongated) of grains in the Claret Formation might suggest more sustained floods, but similarity in the 90^th percentile of grain size suggests the floods could have had similar peak discharges. These results suggest that changes in interannual discharge variability may play an important role in river activity during global warming events.