Geochemical Approaches to Paleobiology, Paleoclimatology, and Chronostratigraphy of the Cretaceous Cloverly Formation

This dissertation explores the use of geochemical tools to evaluate the timing and nature of biotic and environmental change in the Cloverly Formation. Carbon isotope stratigraphy presented here suggests that the fossiliferous interval of the Cloverly is constrained to mid-late Albian in age, warranting revision of paleoecological comparisons with other late-Early Cretaceous nonmarine deposits. I examine the ecohydrology and paleoenvironment of a local Cloverly fossil assemblage by analyzing the 18O of biogenic phosphates from a large set of vertebrate fossils. This has resulted in the first quantitative surface-air temperature estimate (22.3 +/- ~ 5 °C) for the Cloverly, as well as insights into the water use ecology and hydroclimatic conditions recorded by Cloverly fossils. I estimate the 18O of precipitation from the 18O of turtle and crocodylomorph phosphate and find that our mean estimate of -8.4 +/- ~ 1-2 ‰ vs. VSMOW is consistent with proxy data from other mid-Cretaceous deposits in the Western Interior when adjusted for paleolatitude. I evaluate the amenability of Cloverly sedimentary geochemical archives to paleoclimatic reconstruction. CALMAG and CIA-K weathering indices of paleosol B horizons, along with lithological characters, suggest significant periodic fluctuations in paleorainfall rates (~ 200-1600 mm/yr) and groundwater levels. Petrography, cathodoluminescence microscopy, and C and O stable isotope analyses of sedimentary carbonates suggest that Cretaceous near-surface conditions are recorded. Future work should involve similar approaches applied to additional sites in the Cloverly, as well as the application of novel isotope proxies such as “clumped” and triple oxygen isotopes.

Grantor dc:publisher

University of Kansas

Year dc:date.issued

2024

Author dc:creator

• Allen, Matthew L.

Advisor dc:contributor.advisor

• Suarez, Marina B.

• Geochemistry
• Geology
• Paleoclimate science
• Cloverly
• Cretaceous
• Paleobiology
• Paleoclimate
• Paleoecology
• Stable Isotopes

Language dc:language.iso

en

Dc Identifier Other

http://dissertations.umi.com/ku:19667

OAI identifier oai:identifier

oai:kuscholarworks.ku.edu:1808/38217