HR: 1340h
AN: PP23B-1341    [Abstracts]
TI: Regional water cycle change during the PETM from new records in central Utah and CCSM
AU: * Bowen, G J
EM: gabe@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907, United States
AU: Huber, M
EM: huberm@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907, United States
AU: Bowen, B B
EM: bbowen@purdue.edu
AF: Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907, United States
AB: Isotopic and lithological data from stratigraphic sections in central Utah provide new insight into the evolution of climate in this region during the Paleocene-Eocene thermal maximum, a ~200 kyr pulse of carbon buildup in Earth's atmosphere and global warming. Within the pedogenically modified floodplain clastic rocks of the North Horn Fm., this event is marked by an abrupt negative carbon isotope excursion and a notable positive shift in oxygen isotope ratios of paleosol carbonate nodules. The magnitude of the changes in central Utah carbonate δ¹³C and δ¹⁸O are relatively small and large, respectively, in comparison with equivalent records from the Bighorn Basin (WY) some 500 km to the NNE. These patterns are evaluated in the context of simulations of early Paleogene warm climates made using the NCAR CCSM1.4 fully coupled climate model. They are found to be consistent with the model's predicted N-S gradient in hydroclimatological response to greenhouse forcing, which would have driven a decrease in plant photosynthetic ¹³C fractionation due to changes in water availability and an increase in evaporative enrichment of soil water δ¹⁸O relative to changes at the Wyoming site. The termination of the PETM in the Utah section, as defined by carbonate δ¹³C values, is marked by several meters of braided channel sandstones, perhaps signifying the renewed penetration of moisture into the region and enhanced erosion on a partially de-vegitated landscape. While coupled climate model simulations appear to be consistent with the spatial gradients in PETM hydroclimatology documented by the proxy data, our comparison highlights the need for transient climate model simulations of deep-time paleoclimate events to further investigate model performance relative to records of the temporal component of climate change.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1637 Regional climate change
DE: 4914 Continental climate records
DE: 4928 Global climate models (1626, 3337)
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting