2009 Portland GSA Annual Meeting (18-21 October 2009)

Paper No. 12
Presentation Time: 11:00 AM


MATSON, Samuel D., Department of Geology and Geophysics, University of Minnesota, 108 Pillsbury Hall, 310 Pillsbury Drive SE, Minneapolis, MN 55455 and FOX, David L., Department of Earth Sciences, University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455-0219, mats0159@umn.edu

During the late Neogene, terrestrial systems experienced important global transitions, including floral and faunal turnover associated with the expansion of grassland ecosystems and climate change linked to the onset of northern hemisphere glaciation. In the Mediterranean region, these changes were also accompanied by paleogeographic changes associated with the latest Miocene Messinian Salinity Crisis (MSC). We report a record of terrestrial paleoclimate and paleoecology during the Late Miocene, Pliocene, and Pleistocene of Spain based on the stable oxygen isotope composition (δ18O) of mammal faunas. We use the δ18O of fossil horse tooth enamel to estimate past mean annual temperature (MAT) since enamel δ18O from modern horses is a reasonable proxy for the δ18O of local meteoric water, which is in turn strongly dependent on MAT. We compare our results from Spain with similar data from the Late Miocene of northern Libya to explore regional climate variability during the MSC. We also use δ18O values within faunas to reconstruct physiological and/or habitat diversity between taxa, and we compare intra-tooth samples of enamel and dentine δ18O to examine diagenetic alteration.

Our paleotemperature reconstructions indicate MAT for the terminal Miocene of Spain that is approximately 2-3ºC higher than today, with a difference of approximately 6-7ºC between northern and southern Spain. This latitudinal gradient is only 1.5ºC higher than for these same areas today. The difference between modern and Late Miocene MAT is consistent with global cooling during the late Cenozoic. The δ18O values from Libya are lower than those for southern Spain, suggesting cooler and/or wetter climates in northeastern Africa during the MSC. Intrafaunal δ18O comparisons are consistent with a semi-aquatic lifestyle for anthracotheres, hippopotamids, and castorids. Comparisons of enamel and dentine δ18O values suggest slight diagenetic alteration of dentine, but we demonstrate that these δ18O values can be used to reconstruct reasonable values of diagenetic water δ18O. Overall, our data do not support large climatic changes in the Iberian Peninsula during the MSC, but are consistent with long-term global cooling and Neogene latitudinal climate gradients in Spain that are slightly sharper than today.