A PLIOCENE RECORD OF ICE-RAFTED DEBRIS FROM ICE-PROXIMAL SITE U1359 (IODP EXP. 318), WILKES LAND CONTINENTAL RISE, ANTARCTICA

A reconstruction of ice-rafting history was generated utilizing a high-resolution (3,180 yr) ice-rafted debris (IRD) mass accumulation rate (MAR) record from Integrated Ocean Drilling Program (IODP) Site U1359 from the Wilkes Land continental rise, Antarctica. The record gives insight into the dynamics of polar ice sheets and their relation to climate changes during the Pliocene (~2.7 – 5 Ma). Due to its similarity to present tectonic and oceanographic settings, as well as slightly higher atmospheric CO₂ concentrations, the Pliocene has become the main focus for understanding ice dynamics in response to climate change. Bulk particle-size distributions were determined using a dual light source laser particle size analyzer. IRD MAR were calculated based on the course fraction (>125 microns) and corrected for environmental and depositional parameters. The record shows three major intervals of ice-rafting events in the early Pliocene concordant with positive excursions within the foraminiferal benthic isotope record during periods of increasing IRD MAR. The results suggest an expansion of the ice sheet within the Wilkes sector during glacial phases. Additionally, scanning electron microscope (SEM) assisted microtextural analysis of selected high IRD MAR peaks shows a dominance of glacially influenced quartz sand grains, further suggesting that these high peaks of IRD MAR are the result of iceberg rafting. Antarctic ice-rafted debris records can also be correlated to variations of cyclic events such as orbital forcing. A time series analysis was performed in order to isolate strong cyclic signals within the IRD MAR record.