EOCENE CARBONATE DISSOLUTION EVENTS IN NORTHWEST PACIFIC OCEAN

A series of carbon isotope excursions (CIEs) mark variations in the global carbon cycle and significant changes in climate through the early Paleogene. The Paleocene Eocene Thermal Maximum (PETM) ca. 56 Ma is the most pronounced and well documented of these events, having been described in many sections across the globe. The large CIE across the PETM is marked by a clay rich layer in many deep‐sea sections, resulting from widespread carbonate dissolution on the seafloor, which is in turn related to shoaling of the carbonate compensation depth and lysocline. Several studies have suggested that other CIEs have a similar response, but this information is sparse. There is also debate as to how carbonate preservation in the ocean floor varied over the long‐term climate change of Eocene. Following the prolonged greenhouse warming of Early Eocene Climate Optimum (~53-50 Ma), overall climate started cooling. However, this long-term cooling was also punctuated by transient warming events and increased carbonate dissolution in deep sea carbonates. Such instances have sparsely been addressed in perspective of global carbon cycling. Here we present changes in quality and quantity of carbonate preservation in Eocene sediments at ODP Site 1209 (Shatsky Rise, northwest Pacific Ocean) to record vertical movement of lysocline through the Eocene. Combination of carbonate content record along with magnetic susceptibility and lysocline dissolution indices tied with carbon and oxygen isotopic record from bulk sediments gives a robust scope to understand lysoclinal dynamics of the Eocene and how early Eocene hyperthermals and middle-late Eocene transient warming events are related to changes in lysocline and in turn with quality and quantity of carbonate preservation at Site 1209. Such documentation allows us to better constrain relation of global warming and sea floor carbonate preservation in both short and long term warming periods.