Fossil gastropod proxies reveal paleoenvironmental changes in the White River Badlands, SD, at the Last Glacial Maximum

Author

Corinne RenshawFollow

Date of Award

2025

Document Type

Honors Thesis - NSU Access Only

Degree Type

Bachelors of Science

Degree Name

Marine Biology

Department

Halmos College of Arts and Sciences and the Guy Harvey Oceanographic Research Center

Honors College

Farquhar Honors College Thesis

Honors College Dean

Andrea Nevins

Home College Dean

Holly Baumgartner

Faculty Advisor

Paul Baldauf

Abstract

The Laurentide Ice Sheet expanded and retreated asynchronously across North America during the Last Glacial Maximum, producing regional differences in temperature, atmospheric circulation, and precipitation patterns. In central North America, cold, arid conditions caused by the local glacial maximum (~25 ka) resulted in regional desertification and dust storms. To understand how aeolian transport of dust-sized particles varied as a function of precipitation at this time, we analyzed δ¹⁸O values in fossil gastropod shells alongside loess deposition rates. Among other influences on shell δ¹⁸O, like water vapor, relative humidity, and evaporation, we hypothesized that if greater rates of loess accumulation coincide with negative deviations in shell δ¹⁸O, decreases in regional precipitation may be related to aeolian activity and regional dust transport. Gastropod fossil shells were collected from the White River Badlands, a region in the northwestern Great Plains where paleoclimate is poorly constrained, due to the lack of traditional paleoclimate proxies such as trees, lake sediments, and charcoal. The gastropod fossil shell species, Galba obrussa, Vallonia gracilicosta, Pupilla hudsonium, and Gyralus parvus, had radiocarbon ages from 24.6 to 21.7 ka, spanning most of the Last Glacial Maximum (~26.5–19 ka). Negative δ¹⁸O_shell values from 24–22 ka aligned with high loess accumulation rates (>2 mm/yr), indicating that significant regional desertification and reduced precipitation continued about two thousand years after the Laurentide Ice Sheet had reached its maximum southwestern extent. Ongoing desertification in this region following the local glacial maximum is owed to residual climate effects inflicted by the Laurentide Ice Sheet's earlier proximity, including expanded high-pressure systems, depleted moisture sources, and strong surface winds.

NSUWorks Citation

Corinne Renshaw. 2025. Fossil gastropod proxies reveal paleoenvironmental changes in the White River Badlands, SD, at the Last Glacial Maximum. Capstone. Nova Southeastern University. Retrieved from NSUWorks, Halmos College of Arts and Sciences and the Guy Harvey Oceanographic Research Center. (43)
https://nsuworks.nova.edu/honors_theses/43.