See more from this Division: Pardee Keynote Sessions
See more from this Session: Critical Zone Studies of Soils and Weathering: Implications for Interpreting Climate and Landscapes of the Past
Abstract:
Application of this phyllosilicate stable isotope paleothermometer to 115 samples of Upper Cretaceous (~70 Mybp) through Miocene (~5 Mybp) paleopedogenic kaolinites that formed between ~65°N and ~65°S provides the following results: (1) Data from low-latitude paleotropical sites is sparse (n=2), and appears to be similar to (but perhaps slightly warmer than) modern surface temperatures. (2) Data from mid-latitude sites indicate paleotemperatures that were consistently higher than modern, iso-latitudinal, sites. Specifically, kaolinite ?D and ?18O values provide paleotemperature estimates that are +10°C in Cretaceous, +7°C in Paleocene, +9°C in Eocene, +6°C in Oligocene, and +7°C in Miocene samples compared to modern MAAT. Carbon-mass flux estimates of paleoatmospheric PCO2 are poorly correlated (r2 = ~0.5) with these stable isotope estimates of paleotemperature, whereas geochemical estimates of paleoatmospheric PCO2 from pedogenic minerals are much better correlated with these paleotemperature estimates (r2 = 0.7), and suggest that temperatures in the mid-latitudes increase by ~2.4°C with each doubling of atmospheric PCO2 concentrations compared to modern, pre-industrial, values.
See more from this Division: Pardee Keynote Sessions
See more from this Session: Critical Zone Studies of Soils and Weathering: Implications for Interpreting Climate and Landscapes of the Past