a sedimentological record of early miocene ice advance and retreat and 2a drill hole mcmurdo sound antarctica

n/

Continental-scale geographic change across zealandia during paleogene subduction initiation

Data from International Ocean Discovery Program (IODP) Expedition 371 reveal vertical movements of 1-3 km in northern Zealandia during early Cenozoic subduction initiation in the western Pacific Ocean. Lord Howe Rise rose from deep (~1 km) water to sea level and subsided back, with peak uplift at 50 Ma in the north and between 41 and 32 Ma in the south. The New Caledonia Trough subsided 2-3 km between 55 and 45 Ma. We suggest these elevation changes resulted from crust delamination and mantle flow that led to slab formation. We propose a "subduction resurrection" model in which (1) a subduction rupture event activated lithospheric-scale faults across a broad region during less than ~5 m.y., and (2) tectonic forces evolved over a further 4-8 m.y. as subducted slabs grew in size and drove plate-motion change. Such a subduction rupture event may have involved nucleation and lateral propagation of slip-weakening rupture along an interconnected set of preexisting weaknesses adjacent to density anomalies

A Pleistocene warming event at 1 Ma in Prydz Bay, East Antarctica: Evidence from ODP Site 1165

Magneto-stratigraphic and nannofossil assemblage data from ODP Site 1165 evidence an anomalous warming event of the surface waters in and around Prydz Bay during the Early Pleistocene. This results from an increase in the abundance of nannofossils at Site 1165, that occurred at 1 Ma. High-resolution sampling permits a new bio-magnetostratigraphic interpretation for ODP Site 1165. A decrease in δ18O values at Sites 1165 and 1167 also occurs at this time, supporting the presence of warming conditions in the Prydz Bay area. A return to colder surface waters, indicated by the absence or rare occurrence of nannofossils in the upper cores from Site 1165, suggests that more stable glacial conditions existed in the Prydz Bay basin for the last 900 ka. These new evidences call for a re-evaluation of the notion that the East Antarctic Ice Sheet has experienced stable conditions similar to today since the late Neogene