A CONTINENTAL SCENARIO FOR THE PETM: PEAT/COAL CAPACITOR, OROGENIC/CLIMATIC TRIGGER

The magnitude of the carbon isotope excursion (CIE) during the Paleocene-Eocene Thermal Maximum (PETM), and the extent of oceanic acidification at its onset, suggest >4500 Gt of carbon were released from a carbon reservoir that was isotopically moderately depleted (Zachos et al. 2005), possibly from burning or oxidation of Paleocene peat and/or coal (Kurtz et al. 2003). A continental scenario for the PETM includes: 1) extensive deposition of peat and coal during the middle Paleocene, 2) increased oxidation and/or burning of organic deposits such as those in the northern Rocky Mountain coal basins during the late Paleocene as uplift of mountains created a rain shadow, 3) global greenhouse warming and poleward shift of subtropical high pressure as a result of higher atmospheric pCO2, and, 4) rapid acceleration of peat/coal oxidation as global and regional climate change affected major mid- to high-latitude coal basins at the start of the PETM. The scenario is consistent with the timing of uplift and the onset of red-bed formation in the northern Rockies, with the inference of rapid drying at the base of the PETM from fossil leaves, and with the larger magnitude of the CIE in continental than marine carbon reservoirs. In contrast to clathrate or thermogenic methane scenarios for the PETM the continental scenario predicts a faster onset of the CIE in continental than in marine sections, and increased evidence for burning and/or oxidation of organic matter in major coal basins during the late Paleocene, with a peak at the beginning of the PETM.

J. C. Zachos et al., 2005, Science 308, 1611. A. C. Kurtz, et al., 2003, Paleoceanography 18, 1090.