BIOGENIC OPAL PRODUCTION IN THE AGULHAS CURRENT AND ITS CONNECTION TO ARIDIFICATION IN SOUTH AFRICA DURING THE MID-PLEISTOCENE

Abstract- We present a record of biogenic opal production near the Agulhas Current and Benguela upwelling region from IODP Site U1479, collected during Expedition 361. Records from ODP Leg 177, Sites 1090 and 1089, suggest arid climates in South Africa, as suggested by net productivity of diatoms at these sites. A change from obliquity to eccentricity cycles dominated the Mid-Pleistocene Transition (MPT) (800kyr-1.07 Ma), which led to an increase in ice mass during glacial periods. Glacial and interglacial changes caused fluxes in biogenic silica transport in the Agulhas Current and the Benguela upwelling region. With the biogenic opal % we infer significant increases in nutrients to the site during the onset of the MPT. We are tracking opal % fluxes in U1479 from Marine Isotope Stage-18 (MIS-18) to MIS-21, around 800 kyr, to evaluate nutrient fluxes and production, and relate it to the distribution of Benguela upwelling events. Our current data include 29 intervals down core at a 10,000-year resolution showing fluxes in the biogenic silica during the MPT. Preliminary results indicate that during about 770-855kyr there was an increase in biogenic silica production, similar to the observed event at ODP Sites 1090 and 1089. With improvements in the age model we hope to solidify this high production event of biogenic silica to better understand the timing in relation to Sites 1090 and 1089 and other Benguela upwelling studies.