GSA Connects 2021 in Portland, Oregon

Paper No. 130-5
Presentation Time: 9:05 AM


RUSH, William, University of California, Santa Cruz Earth and Planetary Sciences, 1156 High St, Santa Cruz, CA 95064-1077, ZACHOS, James C., Earth and Planetary Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, BLACKBURN, Terry, University of California, Santa Cruz, 1156 High Street EMS A232, Santa Cruz, CA, CA 95064, FINNEGAN, Noah J., Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064 and VON STRANDMANN, Phillip Pogge, University College London, London, United Kingdom

The Paleocene-Eocene Thermal Maximum, or PETM, was a period of rapid warming c. 56 mya that provides one of the closest analogues to present day anthropogenic climate change. As a result of this rapid warming, there were significant disruptions to the hydrologic cycle on both global and regional scales. Many locations experienced increases in sedimentation rates and an influx of kaolinite as a result of these hydrologic changes, but there are disagreements as to the interpretations of these records, with some attributing the influx of kaolinite to intensified chemical weathering associated with warmer, wetter conditions and others attributing the influx to intensified physical erosion excavating previously formed kaolinite sourced from Cretaceous-aged laterite deposits. Located on the Mid-Atlantic Coast of the United States, the Salisbury Embayment contains a well-preserved sequence of PETM sediments with a well-documented increase in kaolinite content as well as several other indicators of significant hydrologic changes. Published climate model output demonstrates changes in both the intensity and seasonality of precipitation in the region. Previous work on the sediment provenance in this region suggests the sediment contained in the PETM section was reworked on the basis of biomarkers suggesting more thermally mature organic material in the PETM section than the underlying or overlying sections, and a shift in the oxygen isotopic composition of the clay minerals. This study seeks to build on this work by incorporating radiogenic Sr and Pb isotopes of the siliciclastic fraction of sediment to serve as a fingerprint for the sediment sourcing, and Li isotopes to provide insight into changes in sediment transport. Preliminary results indicate a significant shift in both the Sr and Pb isotopes at the Paleocene-Eocene boundary consistent with a change in sediment sourcing, with a divergence in the Sr and Pb trends continuing after the PETM. Likewise, Li isotopes demonstrate a negative excursion at the P-E boundary suggesting a shift to a kinetically-limited, transport-dominated system relative to the late Paleocene.