Semester of Graduation
Spring 2025
Degree
Master of Science (MS)
Department
Department of Geology and Geophysics
Document Type
Thesis
Abstract
The Paleocene-Eocene Thermal Maximum (PETM) was a ~200 ka period of rapid global warming in the earliest Eocene (~56 Ma) involving a roughly 7 °C rise in atmospheric and sea-surface temperatures. The Gulf of Mexico Wilcox Group contains very well-preserved terrestrial and deltaic sediments that contain exploitable hydrocarbons . The Wilcox Group’s Paleocene Tuscahoma and Eocene Hatchetigbee Formations have been roughly dated with calcareous and planktonic foraminiferal assemblages by AMOCO; however, the precise ages of these formations, their palynological assemblages, and their paleo-depositional geosystems are an area of active research.
Through a high-resolution palynological analysis, this study assesses the depositional model of the onshore Paleocene-Eocene Gulf Coast Plain stratigraphy, describes the paleo-environments of four Paleocene-Eocene sites, and correlates changes in depositional environments with extinction events associated with the PETM. To achieve this, we conducted a palynological analyses of 92 samples from four AMOCO-legacy Paleocene-Eocene outcrops in the southern United States, specifically in Mississippi and Alabama. The sediment was deposited in coastal to marine environments. Historical reports from the AMOCO Research Department suggested that this study area contained evidence of the Paleocene-Eocene boundary, but those reports did not define the Paleocene-Eocene Thermal Maximum or attempt any paleoenvironmental reconstructions.
Pollen assemblages in these samples are dominated by the Betulaceae/Myricaceae group, the Momipites/Caryapollenites group, Thomsonipollis magnificus, Taxodium hiatipites, and other gymnosperm pollen. The dominant dinoflagellate cysts recovered are Apectodinium spp., Adnatosphaeridium spp., and Eocladopyxis spp.
The high resolution biostratigraphic zonation of the Wilcox Group we established for the eastern Gulf Coast Plain indicates that extinction events associated with the PETM begin within the upper Tuscahoma Formation, rather than the Tuscahoma-Hatchetigbee boundary, as originally interpreted in the historical reports. Shifts in the palynological assemblages indicate that the subtropical, humid lowland forest and swamp paleodepositional environments of the late Paleocene at our study locations were rapidly replaced by shallow, neritic paleodepositional environments at the onset of the PETM, consistent with eustatic sea level rise caused by global warming. These results help to refine regional paleo-coastline reconstructions across the Paleocene/Eocene boundary.
Date
3-26-2025
Recommended Citation
Bancroft, Sarah Fortin, "Evaluating Biotic Effecrs Associated with the Paleocene-Eocene Thermal Maximum in Mississippi and Alabama: A Palynological and Biostratigraphic Study of AMOCO's Legacy Samples" (2025). LSU Master's Theses. 6103.
https://repository.lsu.edu/gradschool_theses/6103
Committee Chair
Warny, Sophie
