Identifying Ice-Rafted Debris Offshore of Antarctica Using a Multi-analysis Approach

The Antarctic Ice Sheet (AIS) has undergone accelerated mass loss in recent decades, primarily driven by the intrusion of warm water masses and the thinning or collapse of ice shelves, with significant implications for global sea-level rise. However, long-term AIS variability in response to climatic forcing remains poorly constrained beyond the satellite observational record. Ice-rafted debris (IRD) preserved in marine sediment cores offers a critical proxy for reconstructing past iceberg discharge and glacial dynamics along the Antarctic margin. This study applies a multiproxy framework to identify and characterize IRD in legacy sediment cores from the Weddell Sea and George V Land continental margins. Analytical methods include laser particle size analysis (LPSA), grain shape metrics, magnetic susceptibility (MS), elemental geochemistry (XRF), and scanning electron microscopy (SEM) of quartz grain microtextures. Results reveal pronounced spatial variability in IRD deposition, with the highest abundance and variability recorded in Weddell Sea continental slope cores. These IRD-bearing intervals are characterized by poorly sorted, coarse-grained sediment enriched in Fe, Ti, and Zr, alongside elevated MS values— indicative of episodic lithogenic input from iceberg rafting and subglacial sediment delivery. In contrast, abyssal plain and George V Land cores exhibit finer-grained, more uniform sedimentation and less frequent IRD input, consistent with greater distance from grounding line sources. Statistical analyses, including correlation matrices and principal component analysis (PCA), demonstrate strong covariation among maximum grain size (D100), MS, and terrigenous elemental concentrations in IRD-bearing layers. The diagnostic power of this multiproxy approach is formalized through an IRD index (0–4), which integrates multiple independent indicators to classify IRD presence across cores. These findings underscore the complex, regionally variable nature of IRD delivery in Antarctic margin sediments and contribute a refined methodological framework for paleoenvironmental reconstructions of AIS dynamics and iceberg discharge histories in polar marine settings.