Grain-size Sensitivity of IRD Reconstruction Across the Mid Pleistocene Transition: A Study from the North Atlantic IODP Site U1564

Authors: Ifeoluwa Salami, Molly Patterson, Halima Ibrahim

Field of Study: Geological Sciences

Program Affiliation: Paleoclimate Lab

Faculty Mentors: Molly Patterson

Easel: 48

Timeslot: Afternoon

Abstract: Reconstructing ice-sheet dynamics via ice-rafted debris (IRD) is complicated by inconsistent size-fraction definitions and quantification methods. These discrepancies yield divergent reconstructions, hindering the synthesis of Northern Hemisphere ice-sheet behavior. This study addresses these challenges using sediments from IODP Site U1564 (Gardar Drift) spanning the Mid-Pleistocene Transition (~1.25–0.7 Ma). By quantifying sieved weight percentages across multiple fractions (63 μm, 63-150, >150 μm) and performing manual lithic grain counts (>150 μm), it was systematically evaluated how methodological choices influence inferred IRD variability. This research provides a framework for standardizing IRD records in high-energy contourite systems where bottom-current "noise" can bias finer fractions. Ultimately, this work improves quantitative interpretations of iceberg discharge and its role in the emergence of the modern 100,000-year glacial climate regime.