Knowledge Bank

Marine sediment cores, retrieved from Ocean Drilling Program Leg 198 Site 1209 Hole C Core 11 Section 3, at Shatsky Rise in the Pacific Ocean, captures a very distinct interval of time in Earth history called the Paleocene- Eocene Thermal Maximum (PETM). These sediments have distinct enrichments of the mineral barite which can record the changes in the ocean primary production. The Earth warmed during this rapid global event due to carbon injection into the atmosphere. The main intent of this study was to analyze key intervals of the core to decipher the marine barite content over the PETM. Specifically, it investigated how the barite accumulation was affected by the warming in the oceans. To test the hypothesis of an increase in pelagic marine barite accumulating during the warming and the recovery from the event, I separated barite from deep-sea sediments and then analyzed the resulting residue under the scanning electron microscope, using backscattered electron imaging and energy dispersive X-ray to determine its composition. The results suggest that there was a wide range of barite size and shape as well as other refractory sediments in the residue. Evidence for dissolution and recrystallization of barite was seen in the core with little barite recovered during the recovery from the PETM. Overall, the results were inconclusive, but generally inconsistent with previous work that suggest enhanced carbon export from the surface of the ocean during the recovery period from the Paleogene greenhouse event. Instead changes in the chemistry of the sediments or water column during the PETM appears to have altered the barite crystal shape and content (due to dissolution and recrystallization) at this site.