Semester of Graduation

Spring 2026

Degree

Master of Science (MS)

Department

Department of Geology and Geophysics

Document Type

Thesis

Abstract

Marine gateways regulate the exchange of water, nutrients, heat, and salt between oceanic basins, exerting strong control on global circulation and climate. The Mediterranean–Atlantic gateway, characterized by dense saline Mediterranean Outflow Water, experienced major reorganization during the Late Miocene to Early Pliocene, including the Messinian Salinity Crisis (MSC). This study presents palynological analyses from IODP Expedition 401 Site U1610, located on the Atlantic margin of the gateway off the coast of Spain. Dinoflagellate cysts are used to reconstruct sea-surface conditions, while pollen and spores provide insight into terrestrial vegetation and regional climate along the adjacent Iberian margin. Palynological assemblages indicate persistent fluvial discharge and strong terrestrial influence at Site U1610 throughout the Late Miocene to Early Pliocene, with only subtle variations in marine conditions during the MSC. CREST climate reconstructions derived from the pollen record show relatively stable conditions through time, with mean annual temperatures being cooler and mean annual precipitation being wetter than the modern southwest Iberia. No abrupt climatic shift is observed at the Messinian–Zanclean transition. Pollen assemblage composition reflects a mixed forest–woodland system with herbaceous understory elements, rather than widespread arid steppe or desert landscapes. These results suggest that the MSC was not associated with major terrestrial climatic deterioration along the Iberian margin. Instead, the surprisingly stable environmental conditions during the crisis further supporting hypotheses that the onset, duration and termination of the MSC were primarily linked to tectonic closure and re-opening of the Mediterranean–Atlantic gateway. While marine circulation and basin connectivity changed dramatically at the end of the MSC, terrestrial climate along the southwest Iberian margin evolved gradually and was resilient.

Date

3-26-2026

Committee Chair

Warny, Sophie

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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Available for download on Thursday, March 24, 2033

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