BENTHIC FORAMINIFERA AS PROXIES FOR CLIMATE AND OCEANOGRAPHIC CHANGES IN THE HOLOCENE OFF SOUTHERN CHILE

One of the least explored and most productive regions of the global ocean is the eastern South Pacific Ocean. The West Wind Drift (WWD) controls circulation along much of the Chilean coastline. It approaches the coast at 45°S, where it splits into two unequal water masses, the Peru-Chile Current (PCC) and the Cape Horn Current (CHC). The PCC flows north from 42°S up to 4°S where it turns westward. The CHC flows south from 43°S until it rounds the tip of the continent. South of 52°S in the Magellan Strait, Atlantic, Pacific, and Antarctic waters interact. Latitudinal shifts in the WWD have been noted during the Holocene.

Various proxies, e.g., alkenones, isotope ratios of planktonic foraminifera, biogenic opal, and organic carbon, have been used in recent studies to investigate changes in temperature, salinity, and productivity along the Chilean continental margin (23-41°S) during the Holocene and late Quaternary. None of these studies have used benthic foraminifera as a proxy or focused upon the region south of 42°S. The aim of this study is to use a multiproxy approach to reconstruct oceanographic and climatic changes to determine the effect of the latitudinal shifts of the WWD and changes in the Patagonian Icefields at the entrance to the Magellan Strait.

The present study utilizes cores taken during leg 3 of the R/V MIRAI MRO3-KO4 cruise, which was part of the BEAGLE (Blue Earth Global Ocean Experiment) 2003 program and developed by JAMSTEC. We are working on two cores taken from station 3 at the entrance to the Magellan Strait at latitude 52°52'S and longitude 74°05'W and 560 m water depth. The cores include a multicore which is 26 cm in length and estimated to encompass 345 years of sedimentation (based on ²¹⁰Pb) and a piston core which is 964 cm in length and estimated by preliminary C-14 data to be ~12,000 years old at the base. Data to be collected from these cores will include benthic and planktonic foraminiferal assemblages and Mg/Ca ratios and d¹⁸O from one species of benthic foraminifera, Cibicides dispars, and two species of planktonic foraminifera, Globigerinoides bulloides and Neogloboquadrina pachyderma. We will use these data to reconstruct variations in salinity, temperature, and past oceanic circulation which will be compared with other proxies including alkenones, biogenic opal, and organic carbon.