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40418-G2
Seasonality in the Early Eocene Warm Climate of the U.S. Gulf Coastal Plain

Linda C. Ivany, Syracuse University

The work originally proposed for this award was to evaluate paleoseasonality in the early Eocene of the US Gulf Coast using serially microsampled bivalves and oxygen isotope analyses of shell carbonate. We find that the range of seasonal temperature variation during this interval of maximum warmth is very low, only a few degrees, in comparison with later Eocene records showing up to 8-10 °C variation as mean temperature fell. Across the Paleocene-Eocene transition, stable isotopes show surprisingly little change, suggesting that this very important event in other parts of the world may have had little effect on low latitude shelves.

In addition, funds were used to support two other projects also involving stable isotope analysis of micromilled samples from bivalve shells, one project in the Eocene of Antarctica and one in the Permian of Australia. Nicole Miklus' work on the Eocene paleoseasonality record of Antarctica shows that seasonal range of temperature variation in coastal waters decreased through the Eocene as mean temperatures cooled, winter temperature approached the minimum threshold of freezing, and summers cooled even more. The timing and magnitude of this change offer a good comparison to the low latitude data from the US Gulf Coast, where a minimum temperature threshold is not a factor and so seasonality increases as mean temperature cools. Secondly, collaborative work with Bruce Runnegar at UCLA on bivalves from the Permian of SE Australia has revealed a very interesting pattern of what appears to be primary seasonal temperature/salinity change that may reflect peri-glacial environmental conditions during the waning stages of Permo-Carboniferous glaciation. Ongoing work will test whether the isotope variation is in fact primary or results from diagenetic processes.

Student participation facilitated in full or in part by this grant:

A number of undergraduate students have been involved in parts of this project, collecting data from bulk fossil samples to accompany our climate story for the US Gulf Coast Paleogene, helping to prepare samples for isotope micromilling, and/or doing the milling itself. They were paid off of a combination of this grant and my own departmental funding. Caitlin Keating-Bitonti, Leigh Castellani, Emily Feinberg, Cristina Story, Justina Fedorchuk, Shea Lambert, Tristan Lee-Wright, Justin Bohling, and Michael McHarris all participated in some way. Andrew Haveles was an undergraduate student at SU who has stayed to pursue a Masters degree with, and he is also working on Gulf Coast material.

In addition, Nicole Miklus is completing her Masters degree with me on the record of seasonality through the Eocene on the Antarctic Peninsula. Her high-resolution work micromilling bivalves was funded by this grant in combination with a student research grant from the GSA, and will provide a very interesting comparison to data coming from the lower-latitude US Gulf Coast region.

Jocelyn Sessa is a PhD student at Penn State who is deeply involved with this research. I am one of her committee members. She is focusing on the climatic and paleoecologic record of the Paleocene-Eocene transition in the Gulf using stable isotopes, and has produced quite a bit of data. She will finish her degree over the next year and then join us at SU for a post-doc.

Lastly, Andrew Haveles has begun a Masters degree with me working on aspects of the paleoecology of the US Gulf Coastal Plain. He worked with me as an undergraduate student, funded in part on the PRF grant, and decided to stay on in order to get more involved in the project. He will use microsampling and isotope analysis to understand growth rates and longevities of mollusks in the Eocene Gosport Sand, a unit hypothesized to record unusually high rates of primary production.

Student theses resulting from this grant:

Erin Fenlon – “Quantifying the morphology and reconstructing the phylogeny of venericard bivalves along the Gulf Coastal Plain during the Paleocene and Eocene” (College of William and Mary senior honors thesis, 2007) – this thesis arose from the PRF Summer Research Fellowship that I was awarded with Rowan Lockwood at the College of William and Mary; I was Erin's co-supervisor)

Nicole Miklus – “The response of temperature seasonality to global Eocene cooling” (Syracuse University Masters Thesis, expected Fall 2007)

Jocelyn Sessa – “Alpha-diversity and abundance distributions of Paleocene-Eocene molluscan faunas of the US Gulf Coastal Plain” (Pennsylvania State University Dissertation; I am an external committee member)

Additional funding secured as a result of preliminary data from this grant:

National Science Foundation Sedimentary Geology and Paleobiology EAR-0719645

“Collaborative Research: Exploring the Links among Climate, Ecology, and Evolution in Paleogene Marine Faunas of the U.S. Gulf Coastal Plain”

Co-PIs: Rowan Lockwood (College of William and Mary) and Warren Allmon (Paleontological Research Institution and Cornell University); 9/01/07 – 8/31/10

Syracuse is lead institution

$156,124 to SU

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