SEDIMENT RECORDS OF ICE-SHEET INSTABILITY AT ODP SITE 697 (JANE BASIN), NW WEDDELL SEA, SOUTH ORKNEY MICROCONTINENT

The instability of the East and West Antarctic Ice Sheets, WAIS/EAIS, threatens global coastal populations and, when completely melted, could result in an approximate 70 m sea-level increase. Environmental models suggest that anthropogenic change will cause environmental conditions to mimic atmospheric conditions of the Pliocene (5.33 to 2.58 mya) a slightly warmer (~2-3 ℃) epoch with CO₂ concentrations (around 400 ppm) similar to present. The Jane Basin, a small back-arc basin southeast of the South Orkney Islands, is capable of capturing geologic material from around Antarctica as it is centrally located beyond the tip of the Antarctic Peninsula. Here we examine marine sediment records from the Ocean Drilling Program (ODP) Site 697 (Jane Basin) including: grain size analyses, ice-rafted detritus (IRD) provenance, biogenic silica (bSi), XRF elemental counts, and ⁴⁰Ar- ³⁹Ar dating which constrain Antarctic ice-sheet instability and prevailing environmental conditions during the early Pliocene.

Variations in biogenic silica (bSi) from the remains of deceased primary producers, and ice-rafted detritus (IRD), terrigenous sediment (>63 μm) deposited by glaciers, suggest that interglacial periods occurred throughout the early to mid-Pliocene. Fe, S, and Ba counts from XRF analysis will be utilized to further constrain understanding of paleo-productivity while ⁴⁰Ar- ³⁹Ar dates from hornblende and biotite grains found in the IRD fraction (150- 500 μm) will be used to determine regions of Antarctic ice-sheet instability as they can be linked to compositional differences in bedrock. Source regions can be used to determine paleo-ocean circulation as composition can be used to track the movement of icebergs in the Weddell Gyre and Antarctic coastal current.