Paper No. 3
Presentation Time: 8:45 AM


GALLAGHER, Timothy M., Department of Earth and Environmental Sciences, University of Michigan, 2534 C.C. Little Building, 1100 North University Ave, Ann Arbor, MI 48109 and SHELDON, Nathan D., Earth and Environmental Sciences, University of Michigan, 2534 CC Little Building, Ann Arbor, MI 48109,

While marine records often reflect shifts in global climate, terrestrial records tend to be more regionally variable. Paleosols offer a long-term, time-averaged climate archive with established proxies that quantify annual climate variables, including mean annual temperature and precipitation. However, important aspects of terrestrial climate, such as seasonality, are often difficult to constrain. A combination of mean annual and warm season temperatures proxies would allow for a more complete characterization of terrestrial paleoclimate.

Here we investigate the utility of paired paleosol whole-rock geochemistry and pedogenic carbonate Δ47 data. Whole-rock geochemical proxies developed for paleosols can be used to estimate mean annual temperature, whereas the Δ47 of pedogenic carbonate is thought to represent warm month temperatures. We first applied this approach to modern soils with instrumental climate records from Arizona, New Mexico, and South Dakota as a proof of concept. Insights from that work were then applied to paleosols from the Ebro Basin of Spain that span the Eocene-Oligocene transition, a global event characterized by declining temperatures and falling atmospheric pCO2. Previous results from this section suggest that chemical weathering decreased across the transition in response to decreasing atmospheric pCO. However, estimates of mean annual temperature and precipitation remained unchanged, as in many Eocene-Oligocene transition records from endorheic basins. This paradox may potentially be explained by decreasing summer temperatures as recorded by Δ47 values of pedogenic carbonates.