Australia: The Land Where Time Began

A biography of the Australian continent 

Palaeocene-Eocene Thermal Maximum (PETM) – Palaeohydrologic Response to Continental Warming, Bighorn Basin, Wyoming

During the Palaeocene-Eocene Thermal Maximum (PETM) global warming that was geologically rapid occurred ~56 Ma. It has been argued, based on several studies, that during the PETM important changes in the hydrological cycle occurred, though results have been inconsistent, covering a range from increases in global humidity to drier conditions. During the PETM changes in palaeosols in the southeastern Bighorn Basin documented major drying during the body of the event. Transitional episodes of climate change that both preceded and followed the PETM are suggested by changes in palaeosols. A high-resolution record of changes in soil moisture and precipitation is provided by Qualitative, semi-quantitative and fully quantitative analyses of a ~70 m thick interval in palaeosols. These changes are compared to temperature changes that were determined from δ¹⁸O values of tooth enamel from Coryphodon, a mammal. Just before the PETM there was a distinct shift to drier soils, which is a conclusion that is consistent with previous observations that prior to the negative carbon isotope excursion associated with the PETM, warming had already begun. In the lower part of the PETM palaeosols show a trend of drying, becoming even drier in the upper part of the body of the PETM. During the recovery phase of the PETM purple-red palaeosols appear indicating that the soils were wetter, though they are drained better than palaeosols below the onset. Continuing for ~15 m above the recovery the purple-red palaeosols indicate that wetter soil conditions persisted after the recovery. It is not clear if global forcing factors like orbital cycles or carbon release lacking an isotopic label are reflected in the palaeosols that preceded and followed the PETM, however a unifying explanation for shifts seen in continental and marine environments would be provided by such mechanisms.

Sources & Further reading

1. Kraus, M. J., F. A. McInerney, S. L. Wing, R. Secord, A. A. Baczynski and J. I. Bloch (2013). "Paleohydrologic response to continental warming during the Paleocene–Eocene Thermal Maximum, Bighorn Basin, Wyoming." Palaeogeography, Palaeoclimatology, Palaeoecology 370(0): 196-208.