A link between the paleoenvironment and PETM via trace element proxies in Southwest Atlantic sediments

Abstract

To investigate paleo-ocean environmental variations during the Paleocene Eocene Thermal Maximum (PETM), we conducted a geochemical analysis of high-resolution sediment samples from ODP Site 1267 in the Southwest Atlantic. Our results suggest that volcanic materials may have been introduced into the ocean prior to the negative carbon isotope excursion (CIE), while terrestrial debris became the predominant input during the recovery phase of the CIE. Characteristic shifts in trace metal enrichment factors (e.g., Mn_EF, Mo_EF, Ni_EF, Cu_EF, Co_EF) indicate a transient period of hypoxia in the bottom seawater of the Southwest Atlantic during the onset and development phase of the CIE, likely caused by the oxidation of methane released from the seafloor. Elevated levels of nutrient elements (e.g., Sr/Ca ratio, biogenic barium [Ba_bio], and organic phosphorus [P_org]) in sediments suggest a sustained increase in primary productivity during both the development and recovery phases of the CIE. This increase is likely linked to hypoxic and acidic conditions during the development phase of the CIE and the influx of terrestrial debris during the recovery phase of the CIE. Ocean hypoxia and acidification likely facilitated the release of phosphorus and barium from sediments, which were transported to surface seawater via upwelling, further stimulating primary productivity. Additionally, intensified continental weathering during the recovery phase of the CIE contributed to sustained growth in productivity. The high-resolution trace element analysis provides critical insights into the temporal and causal relationships among volcanic activity, ocean hypoxia, enhanced weathering, and increased productivity during PETM events.