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Australia: The Land Where Time Began |
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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.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |