227-7 Glacial and Oceanic Sediment Delivery to the Former Larsen-A Ice Shelf Marine Embayment, Antarctic Peninsula

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology (Posters)

Presenting Author:

Authors:

Abstract:

The 1995 collapse of the Larsen-A Ice Shelf was one of the earliest modern examples of abrupt ice-shelf disintegration along the Antarctic Peninsula. Unlike the Larsen-B Ice Shelf, the Larsen-A has collapsed and reformed multiple times throughout the Holocene (Brachfield et al., 2003). Sediment gravity flows, including turbidites, move material from the grounding-line into proximal mini-basins. These sediment packages, delivered instantaneously by geological terms, are interspersed with background glacial-marine sedimentation. This study examines a sediment core to assess the number and thicknesses of discrete sediment packages as a proxy for grounding-line position. Alternatively, changes in sedimentation patterns may not reflect grounding-line position directly, but rather a shift in the abundance of meltwater and sediment being driven to the core site.

Marine sediment core NBP1203-JC21, collected 8 kilometers from the Larsen-A Ice Shelf front, is 18.19 meters long and was obtained as part of the LARsen Ice Shelf System, Antarctica (LARISSA) project. Core analyses include CT scans, X-radiography, magnetic susceptibility, and laser particle size measurements. The core contains multiple sharp-based graded intervals interpreted as turbidites. These deposits interrupt background laminated silt and sand and are distinguished by abrupt shifts in grain size, bulk density, and magnetic susceptibility.

Preliminary observations suggest that the fining-upward sequences reflect discrete sediment remobilization events, possibly triggered by subglacial meltwater discharge. Grain-size distribution analysis is ongoing to better characterize these deposits in each layer through the core. Future work will include an attempt to make an age model for the core, allowing quantified estimates of the changing rates of sediment delivery over periods of grounding-line fluctuations. This study demonstrates how dynamic grounding-line processes are recorded in marine sediment facies and supports broader reconstructions of glacial retreat along the eastern Antarctic Peninsula.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10485

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.