[Eoas-seminar] Chance Hannold - Dissertation

[eoas-seminar at lists.fsu.edu]

Good afternoon,

Please join us for Chance Hannold's Dissertation on Friday, October 30, 2026, at 3:00 PM in EOAS 4067.

Title: “Environmental Changes as the Principal Driver of Biogeographic Processes in Late Cenozoic North America: Stable Isotopic Evidence from Mexico and California”


Name: Chance Hannold

Date: 10/30/2026

Time: 3:00 PM

Location: EOA 4067    

Major Professor: Dr. Yang Wang



Abstract: This dissertation investigates whether climate-induced environmental changes can explain biogeographic trends of mammals in the Americas during the Neogene and Quaternary, including the expansion of C4 grasslands, dispersals associated with the Great American Biotic Interchange (GABI), and speciation and extinction events of gomphotheres and mammoths. Using stable isotope analyses of fossil tooth enamel and soil carbonates from Mexico and fossil teeth from California, this study reconstructs paleoenvironments and paleodiets of horses and proboscideans to explore the relationships between climate, environment, and biogeography. The isotopic evidence suggests that: (1) C4 grasslands emerged earlier in Mexico than in the midlatitudes, but the expansion of C4 biomass was not monotonic and was driven by temperature-induced changes in regional aridity over time; (2) Mexico and the Great Plains were interconnected biogeographically during the early Pliocene, and thus Mexico may have acted as a holding pen for GABI migrants moving southward until the migratory corridor to South America became passable; (3) the cladogenesis of gomphotheres from Gomphotherium occurred in Mexico simultaneously with the expansion of C4 grasslands, and dietary and habitat flexibility allowed the descendant of Rhynchotherium to succeed in a GABI dispersal; and (4) the speciation of the pygmy mammoth from the Columbian mammoth was not driven by dietary differences or climate-induced environmental change, but climate-driven water stress may have contributed to the extinction of both mammoth species. This dissertation demonstrates that a more direct application of stable isotope paleoecology to events of evolutionary and environmental importance can help confirm or reject theories based on morphological studies or limited physical evidence.

Best,
Adea



Adea Arrison

Sr. Academic Program Specialist

Department of Earth, Ocean & Atmospheric Science

[cid:55efa084-f51c-4d64-90dd-961865a23316]<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.eoas.fsu.edu%2F&data=05%7C02%7Ceoas-seminar%40lists.fsu.edu%7Cfc3a88ab08fb48f16c4908df350c9276%7Ca36450ebdb0642a78d1b026719f701e3%7C0%7C0%7C639288000241314312%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=fQqQw5n7JwozV9LWfmdK3OPnPKUXXCuGHkpcu7M5Vk8%3D&reserved=0>


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.fsu.edu/pipermail/eoas-seminar/attachments/20261028/ed949172/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 3433 bytes
Desc: image.png
URL: <http://lists.fsu.edu/pipermail/eoas-seminar/attachments/20261028/ed949172/attachment.png>