SUMMARYThe three sites proximal to the East Antarctic Ice Sheet drilled during Leg 188 across the Prydz Bay continental shelf, slope, and rise provide new evidence of long- and short-term variations in paleoenvironments (i.e., depositional, glacial, and inferred climate) extending from Holocene into Mesozoic times. The shelf site (Site 1166) documents the earliest stages of East Antarctic glaciation from inferred temperate climates (i.e., with vegetation) to transitional environments of proximal glaciers to full glacial and interglacial conditions with intermittently grounded glaciers on the shelf. Site 1167 on the slope samples the latest Neogene sediments that attest to the rapid deposition and variability of onshore erosion areas and glaciomarine depositional settings in front of grounded ice sheets during glacial-interglacial periods. On the continental rise, at Site 1165, the drilling record documents the long-term, lower to upper Miocene transition from temperate to cold-climate glaciation, with superimposed short-term glacier fluctuations since early Miocene time.
These sites document changing paleoenvironments (Fig. 28), with long-period changes that may mark the transition from more temperate times of wet-based onshore glacier systems with fluvial outwash (i.e., before 13-14 Ma; middle Miocene) to cold times of dry-based systems with overdeepened shelf and subglacial deposition (late Miocene and younger). The notable variability in IRD concentrations since middle Miocene time suggests that the transition varied between the temperate and cold glacier systems. The short cyclic variations (at Milankovitch periodicities) recorded by the gray/green (dark/light) facies observed at Site 1165 may track the persistent seaward-landward movements of onshore glaciers and their internal ice streams. The glacier systems provided more terrigeneous sediments (gray facies) during times of glacial advances and less terrigenous sediment during periods of glacial retreat (interglacials; green facies).
Leg 188, together with previous (e.g., ODP Legs 119 and 178) and future Antarctic continental margin drilling transects, can provide the hard-earned proximal geologic samples needed to link the histories of the Antarctic Ice Sheet and the distal ocean-current and climate systems.
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