Paleosols spanning the Paleocene-Eocene (P-E) in the Bogota Basin record an
increase of chemical weathering around the P-E boundary due to climatic forcing. Rock
magnetic properties and major element geochemistry allowed the identification of this
increase in weathering while previously published palynological zones and a U/Pb date in
volcanic zircons (56.13±0.87 Ma) established the P-E boundary in the section. I
identified a significant anomaly in magnetic susceptibility in coalescence with an order of
magnitude increase in all magnetic minerals (magnetite/maghemite, goethite, and
hematite) in the interval within the margin of error of the radiometric age. Pedogenic
features in the paleosols, lack of iron oxides as cement and friability of the sandstones,
and the shallow burial of the section (<500 m) exclude the possibility that magnetic
minerals were formed during burial. Thus, the signal provided by magnetic proxies is
purely climatic. Fe2O3, Al2O3, loss on ignition, and rubification of paleosols also increase
in this interval suggesting an enhancement in chemical weathering and moisture. The
lack of carbonate nodules in this interval and a decrease in SiO2 also indicate an increase of precipitation. Thus I hypothesize that the intensification of chemical weathering may
be related to perturbation of the hydrological cycle of the Paleocene-Eocene Thermal
Maximum (PETM). However, poor reproducibility of the carbon record prevented
confident identification of the negative carbon isotopic excursion (CIE) associated with
the PETM. Therefore, the carbon isotopic record of the section needs to be improved to
verify i) the correlation between the intensified chemical weathering and the CIE, and ii)
to decipher whether the negative feedback of silicate weathering was the mechanism yielding the long-term temperature stabilization of the globe’s surface, as proposed in
University of Minnesota M.S. thesis. December 2011. Major: Geology. Advisor: David L. Fox. 1 computer file (PDF); vii, 56 pages.
Morón, Sara Eugenia.
Paleosol carbon isotope stratigraphy, major oxides, and rock magnetic record of climate change across the Paleocene-Eocene boundary in the Bogota Basin, Colombia..
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.