147-9 From Debris to Data: Reconstructing Antarctic Ice Sheet Changes via Ice Rafted Debris Grain Counts

Session: Climate, Ocean and Environmental Changes Through Earth History: From Marine and Terrestrial Proxies to Model Assessments (Posters)

Presenting Author:

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Abstract:

The abundance of Ice Rafted Debris (IRD) grains within sediment samples from Ocean Drilling Program Leg 119 Site 745B in the Indian Ocean sector of the Southern Ocean reveals the expansion and contraction of the Antarctic ice sheet as it erodes bedrock in correspondence within glacial-interglacial cycles. Data collected from this study span two glacial to interglacial cycles (Marine Isotope Stages, MIS, 47-49, 1.45-1.50 Ma) during the mid Pleistocene transition at a resolution of 2-3 kyr. Results indicate that the highest percentages of IRD are found within the interglacial intervals MIS 47 (at around 1.45 Ma) and MIS 49 (at around 1.47 Ma and 1.49 Ma). A distinct IRD minimum at 1.48 Ma separates the two maxima during MIS 49 creating a double peak spaced about 20 kyr apart. Percent IRD minima also occur during the glacial maxima of MIS 46, 48 and 50 (1.41 Ma, 1.46 Ma, and 1.50 Ma, respectively). The pattern of elevated IRD percentages during interglacial and low percentages during glacial intervals is generally consistent with previous findings from this site (Ehrmann and Grobe,1991), who reported increased IRD deposition during warm intervals at around 1 Ma, interpreted as periods of increased iceberg production. Further work aims to extend the high-resolution record to determine the significance of IRD variations in comparison to global ice volume variations as recorded by benthic foraminifera.

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

doi: 10.1130/abs/2025AM-8284

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