New insights on the post-rift seismic stratigraphic architecture and sedimentary evolution of the Antarctic Peninsula margin (Central Bransfield Basin)

Abstract

A seismic stratigraphic study of the Antarctic Peninsula margin of the Central Bransfield Basin was conducted using seismic and bathymetric data. The study focused on seismic sequences and units deposited after the basin opened, and yield a record of the evolution of the northern-most Antarctic Peninsula Ice Sheet. Two seismic sequences compose the post-rift stratigraphic succession on the Central Bransfield Basin slope platforms. Both sequences are composed of seismic units that record glacial/interglacial cycles and show evidence of the Antarctic Peninsula Ice Sheet having grounded on the continental shelf and slope platform on several occasions in the past. This evidence includes glacial and glaciomarine related sedimentary and erosional features within the seismic units (glacial unconformities, glacial troughs, till wedges, prograded wedges, trough mouth fans, glaciomarine sheet deposits and moraines), which are bounded by glacial unconformities. The Antarctic Peninsula lower slope also registered in its eastern sector the deposition of gravity flow deposits during ice sheet retreat and interglacial stages. The deposition of seismic units on the middle slope produced the present-day step-like profile of the margin composed of wide flat slope platforms and narrow and steep upper and lower slopes. Seismic units show changes in thickness and distribution that record the effect of the physiography and climatic changes on margin sedimentation. These variations produced an overall change from more line-sourced deposition to more point sourced deposition as ice streams evolved. The stacking of units shows a change in the stratigraphic architecture through time, from dominantly progradational (S2) to progradational/aggradational (S1). This change is correlated with a change in the frequency of ice sheet grounding events which was probably driven by a higher rate of eustatic rise and fall in relation with the Mid Pleistocene global climatic change.