34-1 Can an ice-distal IODP site capture signals of West Antarctic Ice Sheet Dynamics across the Mid-Pleistocene Transition? Insights from the South Pacific.

Session: High latitude paleoceanographic discoveries from Scientific Ocean Drilling (IODP, ODP, DSDP). (Posters)

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Abstract:

Understanding past Antarctic ice sheet behavior is critical for parameterizing climate models and hence improving future sea-level rise estimates. The IRDs are continental debris brought in via icebergs both at close and distal sites off Antarctica, and their presence and absence typically indicate growth and retreat of the ice sheet. Ice sheet history can be reconstructed from marine sediment by counting ice-rafted debris (IRD). Here, we present a high-resolution IRD record from the central South Pacific (CSP) (IODP Site U1539, 56°09′S, 115°08′W, 4070m) to investigate Antarctic ice sheet history over the last 1.4 Ma. 

The IRD flux record was generated using X-ray images of sediment cores using a fine-tuned YOLOv11 (Jocher & Qiu, 2024) deep learning model. We present the first model for the CSP, which is trained on full-size X-ray images (1280px, n=1555), allowing it to precisely recognize IRD (mean average precision >75% ) from sedimentary structures, bioturbation, core disturbances, and image processing artifacts. This approach enables automated quantification of IRD flux, grain sizes, and roundness, tasks that are otherwise time and labor-intensive. 

At the CSP, the period between 1.4-1.2 Ma is represented by higher IRD flux (> 20 #/cm²/kyr than the average flux of 0.47 #/cm²/kyr) along with higher abundance of coarse-grained IRD (granule >72,  to pebble>25 above the combined average of 0.4 counts/12cm). IRD flux declines sharply thereafter, with prominent peaks at ~1.05 Ma, ~0.7 Ma, ~0.4 Ma, and ~0.14 Ma, most of which coincide with ice sheet expansion and collapse events recorded in the Ross embayment (McKay et al., 2012). The last 0.8 Ma long record shows a rhythmic pattern of slow or gradual increase in IRD flux followed by a fast decrease, similar to late Pleistocene glacial growth and breakdown. This part of the record shows a prominent saw tooth pattern with major peaks during glacial periods and troughs during interglacial periods. This would imply that after the MPT, Antarctic glaciers reached a critical threshold that led to enhanced iceberg calving and IRD deposition. Radiogenic analysis of IRD is underway, which, when complete, will inform us about the source of these IRDs. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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