EXPLORING THE PALEOCENE-EOCENE THERMAL MAXIMUM: INSIGHTS FROM THE LODO GULCH SECTION, CALIFORNIA

The Paleocene-Eocene Thermal Maximum (PETM) represents a crucial period in Earth's climatic history, characterized by rapid global warming and significant environmental changes. This study investigates the Lodo Gulch section in California, situated within a continental shelf setting, to understand these changes by analyzing geochemical indicators and foraminiferal shifts during this rapid climatic event.

Our research employs a multi-faceted approach to explore the environmental dynamics during the PETM, focusing on the variations in the isotopic composition of organic matter nitrogen and the carbon to nitrogen ratio both as proxies for changes in organic matter composition and export. In addition, samples were characterized by X-Ray Fluorescence (XRF) analysis to determine sediment elemental composition,with a specific focus on elements tracing weathering (Si/Al, Ti/Al, K/Al), redox-sensitive parameters (V/Al, V/Cr, Mn, Fe), and paleo-weathering conditions using indices such as the Weathering Index of Parker (WIP), Chemical Index of Alteration (CIA), and Chemical Index of Weathering (CIW).

Significant variations in the elemental composition of sediments are observed during distinct phases of the PETM. High Ti/Al and K/Al ratios during the carbon isotope excursion (CIE) coincide with elevated weathering indices, suggesting enhanced detrital supply and intense chemical weathering. The V/Cr and V/Al ratios suggest a shift from oxic to dysoxic conditions during the CIE, consistent with shifts in Mn and Fe concentration. Changes in d15N and C/N ratio reveal shifts in organic matter sources, with higher C/N ratios. Elevated C/N ratios reflect a shift towards more land-derived organic material, contrasting with marine-dominated organic inputs before and after the CIE further supporting intensified weathering as a crucial role in climate recovery. These geochemical indicators provide insights into the environmental changes and feedback mechanisms during the PETM, suggesting weathering and organic matter export on continental shelves are important recovery mechanisms subsequent to climate extremes.

This study highlights the importance of exploring past climate analogs to understand earth system dynamics and develop solutions for maintaining biogeochemical cycles and ecosystem resilience.