Climate Change at the Paleocene-Eocene Boundary in the Bogotá Basin, Colombia

Climate change during the Early Paleogene in the Bogotá Basin (Colombia) inferred from paleosol carbon isotope stratigraphy, major oxides, and environmental magnetism

Authors:

1. Sara Morón (a, c)
2. David L. Fox (a)
3. Joshua M. Feinberg (a, b)
4. Carlos Jaramillo (c)
5. German Bayona (d)
6. Camilo Montes (e)
7. Jonathan I. Bloch (f)

Affiliations:

a. Department of Earth Sciences, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN, 55455-0231, USA

b. Institute for Rock Magnetism, University of Minnesota, 100 Union Street SE, Minneapolis, MN, 55455, USA

c. Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Panama

d. Corporación Geológica Ares, Calle 44a # 53-96, Bogotá D.C., Colombia

e. Geociencias, Universidad de los Andes, Calle 1A # 18A-10, Edificio IP, Bogotá D.C., Colombia

f. Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800, USA

Abstract:

Paleosols in the Bogotá Basin, Colombia, record an increase in chemical weathering across the Paleocene–Eocene (P–E) transition. Rock magnetic properties and major element geochemistry exhibit an abrupt change in an interval identified as including the P–E boundary, as established by previously published biostratigraphy and a U/Pb date on volcanic zircons (56.2 ± 1.6 Ma). During the stratigraphic interval that contains the P–E transition, magnetic susceptibility increases significantly, with an order of magnitude higher concentration of magnetite/maghemite and hematite. The preponderance of pure stoichiometric magnetite in the paleosols of this interval indicates that the increase in magnetic susceptibility is due to changes in the rate of pedogenesis, rather than an increase in the erosion of nearby volcanic rocks, which would contribute titanomagnetite. Pedogenic structures preserved within the paleosols, a lack of iron oxides as cement, friability of the sandstones, and previously published thermochronologic data are not consistent with burial diagenesis as an explanation for the origin of the magnetic mineral assemblage. These enhanced pedogenesis and related chemical weathering is also confirmed by increases in the concentration of Fe2O3 and Al2O3 and loss on ignition values. An increase in mean precipitation across this interval is inferred by the lack of carbonate nodules and a decrease in SiO2 in paleosols. Thus, we hypothesize that there was an intensification of chemical weathering during the interval that contains the P–E transition.