Spatial Heterogeneity of Global Organic Matter Accumulation During the PETM

Abstract

The Paleocene–Eocene Thermal Maximum (PETM) was an abrupt global warming event triggered by a massive release of isotopically light carbon. Rapid recovery from the PETM has been attributed to enhanced burial of organic matter (OM). However, the mechanisms and spatial distribution of global OM accumulation remain uncertain. Here, we present new multi‐proxy reconstructions of the hydrological cycle, paleoproductivity, ocean stratification, redox conditions, and OM accumulation across the PETM from Egypt, combined with a compilation of the global OM records. We reveal that intensified bacterial activity and ocean anoxia stimulated OM burial along the southern Tethyan margin during the main body of the PETM, and emphasize that water‐column stratification played a significant role in driving both. Global compilations reveal three patterns in the relationship between land‐sea carbon isotope excursions and OM content. Specifically, limited OM accumulation in terrestrial sediments resulted from sediment dilution and oxidation. In coastal seas and deep‐sea environments, the limited accumulation is attributed to the lack of anoxic conditions and/or elevated primary productivity. In contrast, significant accumulation on the restricted continental shelves at the carbon isotope excursion body results from concurrent higher temperature, intense hydrological cycle, ocean acidification, anoxia, and high primary productivity. Overall, the spatial heterogeneity in OM accumulation was coupled with that of these factors during the PETM. This study provides a geological perspective for this geological engineering strategy of carbon sequestration, emphasizing that site selection for iron fertilization should prioritize anoxic and iron‐limited continental shelves, where carbon sequestration efficiency is likely to be optimal.