A Magnetic Signature of Heinrich Events from a Particle Size Perspective at IODP Sites U1302/03: Proximal observations on sediment transfer from the Laurentide Ice Sheet across the Late Pleistocene

In the Northern North Atlantic (NNA), bulk magnetic property variations reflect changes in ocean circulation and/or the behavior of surrounding ice sheets. Heinrich events (H-events) are lithogenically rich layers linked to Laurentide Ice Sheet (LIS) instabilities whose characteristics are controlled by the depositional environment at the cores location and are often described by increased bulk magnetic concentration and coarse bulk magnetic grain size. Integrated Ocean Drilling Program (IODP) Sites U1302/03 in the Labrador Sea captures an expanded record of these events reflecting gravity flows through the Northwest Atlantic Mid-Ocean Channel with an admixture of ice-rafted debris (IRD) giving rise to a strong expression of H-events 0-6 and H-11. Here, we examine whether these events can be better magnetically discriminated from each other, from other glacially derived sediments, and/or from other processes in the NNA marine sediment record. Using existing bulk magnetic records and XRF data, we analyzed 60 samples that capture these sedimentary processes over the last 150 kyrs. Bulk samples were separated into five size fractions (>63, 32-63, 10-32, 3-10, and <3 µm) and measured for magnetic susceptibility, hysteresis properties, IRM acquisition, and FORCs. Consistent with previous NNA studies, most of the ferrimagnetic fraction is carried in the silt-size range. However, in contrast to background samples, and results from IODP Sites U1305 and U1306 on Eirik Ridge (ER) where magnetic concentrations are highest in the 10-32 and 3-10 µm fractions, H-event magnetizations are highest in the 32-63 µm fraction. H-event samples also possess distinct hysteresis ratios, and ongoing IRM acquisition and FORC analyses support coercivity based, particle size discrimination of LIS-related inputs from other NNA processes and sources. Individual H-events are discriminable based on their hysteresis and remanence properties, suggesting dynamic sourcing over the late Pleistocene. The similarity of the U1302/03 background sediments to the ER IODP sites highlights sensitivity to similar basin-wide processes; differences of distinct horizons (e.g., H-events, IRD, gravity flows) reflects a LIS-related provenance signature that can potentially be utilized to fingerprint LIS sources to the NNA sediment record.