THE SEDIMENTOLOGIC AND MAGNETIC SIGNATURE OF SIKU EVENTS DURING THE LAST GLACIATION IN THREE DIFFERENT DEPOSITION ENVIRONMENTS IN THE GULF OF ALASKA RECOVERED DURING IODP EXP 341

Integrated Ocean Discovery Program (IODP) Expedition 341 sites from the Gulf of Alaska were drilled to investigate the climate and tectonic history of the region. Sites U1417, U1418, and U1419 form a transect from the continental slope to a depth of 4.2 km on the Surveyor Fan, sampling a range of depositional environments, glaciogenic sediment provenances, and North Pacific water masses. Each site is characterized by high, but non-linear, accumulation rates in the late Pleistocene (~15 to 50 ka). Episodic discharge events of the Northern Cordilleran Ice Sheet, named Siku Events, have been interpreted at U1419 from intervals of high ice-rafted debris (IRD) mass accumulation rate (MAR). We use radiocarbon dates and paleomagnetic secular variation to stratigraphically synchronize U1419 with U1417 and U1418 to establish iteratively improving chronologies at all three sites. Using this blended chronostratigraphic approach, we identify coeval intervals and find that the timing of Siku Event 1 (17 to 18 ka) is characterized by high sedimentation rates at all three sites as previously identified at U1419. Magnetic parameters indicative of the concentration and grain size of magnetic minerals for Siku Event 1 suggest that the event at Sites U1419 and U1418 reflect a similar source with varying depositional signatures, whereas U1417 shows a similar depositional pattern to U1418 but appears to be characterized by a different sediment source. This supports the inference that Siku events can be identified in diverse depositional environments along the Northern Cordilleran Ice Sheet margin. Future work will add additional characterizations and extend these observations through earlier Siku Events at all three sites.