USING MARINE SEDIMENT TO DETERMINE PALEOCLIMATE IN THE EQUATORIAL PACIFIC: COCOS RIDGE ODP SITE 1242

The characterization of oceanic sediment can provide information about past climatic events and conditions. Ocean Drilling Program (ODP) Leg 202 collected sediment cores from the deep sea at Site 1242 in water depth of ~1364 meters on the Cocos Ridge off the Pacific coast of Panama in 2001. The samples were collected at an interval of ~16 ky from the top ~285 meters of the core, consisting primarily of hemipelagic nannofossil clays and clayey nannofossil oozes. This sediment has been analyzed to investigate variables of Central American tectonic and climatic conditions from the upper Pliocene through the Holocene, based on the assumption that the nature and amount of terrigenous sediment deposited seaward of the continent are related to the delivery of sediment to the ocean, and thus would reflect changes in physical erosion processes on the continent, as well as circulation within the surrounding ocean. Extraction of the continental component of the sediment, completed by the removal of the biogenic carbonate and silica components and the dissolution of any oxide/hydroxide coatings, allows for the calculation of terrigenous mass accumulation rates. Changes in the sediment flux, along with grain size and magnetic fabric analyses, can help elucidate information about past climatic events, oceanic trends, and prevailing wind patterns. Analyses thus far indicate terrigenous flux amounts ranging between 4.1 g/cm²/ky and 10.9 g/cm²/ky overall with generally lower terrigenous mass accumulation rates towards recent times, and more pronounced changes at ~1.2 and ~0.3 Ma.