7-7 Comparative Paleoecology in the Eutaw Formation of Northeastern Mississippi

Session: Undergraduate Research, Part I (Posters)

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Abstract:

During the Late Cretaceous, a midcontinental ocean known as the Western Interior Seaway deposited sediments in the northeastern corner of Mississippi. This produced a suite of formations, including the Eutaw Formation deposited during the Late Santonian. The Eutaw Formation was deposited as a product of the Upper Zuni 3.0 sequence, a series of oceanic transgressive and regressive episodes, and is divided into the lower, unnamed or “typical” Eutaw and the upper Tombigbee Sand Member.

During the summer of 2025, researchers with the National Science Foundation funded Gulf Coastal Plain Ecology Research Experience for Undergraduates program at the University of Southern Mississippi excavated macrofossils and sediment from two sites near the city of Columbus, in Lowndes County, Mississippi, USA. Each site represented an outcrop of an individual member of the Eutaw Formation. Larger individual fossils were collected along with multiple bags of loose sediment that contained microfossils. After collection, macrofossils were cleaned, while loose sediment was sieved to retrieve microfossils. Specimens were then identified and sorted by taxa and locality. This sampling enabled researchers to investigate the depositional environment and paleoecology of the two localities, with the goal to further solidify the current understanding of Late Cretaceous marine life. It also allowed researchers to compare the fauna between the two members, informing how life may have responded to the fluctuating sea levels. 

Since the summer of 2025, researchers have continued to identify and sort sediment from the sites, revealing more information about the fauna of the unit and potentially allowing for further investigation into the formation’s paleoecology. Researchers now aim to determine if faunal turnover aligns with the current understanding of a higher sea level in the younger Tombigbee Sand, when compared to the older, typical Eutaw. Along with the construction of a full faunal assemblage for each site, additional analysis will be done into the period’s community composition, further informing how the environment shapes species and their ecology.

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