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.