Linda C. Ivany
Department of Earth Sciences
2011-12 European Tour Information
1-12 October 2012
GO TO: Biography | Abstract 2 |Abstract 3
Equator to pole temperature gradients in the Eocene – insights from multiproxy studies of marine shelf macrofossils
The Eocene includes the warmest time interval in the last 65 million years, yet there is still discussion about how much warmer that climate was and how warmth was distributed across latitudes. Oxygen isotope data from deep-sea microfossils are the industry standard for interpreting paleotemperatures, but are limited by uncertainty in both the composition of local seawater from which the carbonate precipitates and in the season of growth of the precipitating organisms.
Accretionary carbonate from marine shelf bivalves can contribute to the resolution of these difficulties because mollusk shells allow for the recognition of seasonal biases in growth and produce enough carbonate to enable independent temperature control using clumped isotopes analysis, a technique currently limited to large sample sizes.
In addition, shells can be collected in situ with sedimentary organic matter, allowing additional temperature control from tetraether analyses. I will present δ18O data through the Eocene from both Antarctica and the US Gulf Coast, many of which are seasonally resolved. Temperature is independently determined in key stratigraphic horizons with these additional proxies, and the resulting water compositions are then used to determine paleotemperatures through time from the more extensive δ18O dataset. Results reinforce the concept of polar amplification of greenhouse warming and show that, while the high latitudes were certainly warm, they may not have been as hot as some recent studies have suggested.