Depositional and erosional signatures in sedimentary successions on the continental slope and rise off Prydz Bay, East Antarctica– implications for Pliocene paleoclimate

The Prydz Bay region of Antarctica is the immediate recipient of ice and sediments transported by the LambertGlacier, the single largest outflow from the East Antarctic Ice Sheet. The continental slope and rise providerecords covering multiple glacial cycles and containing paleoclimatic information. Marine geological and geophysicaldata collected from the continental shelf and adjacent slope of Prydz Bay, Antarctica, including seismicreflection data, bathymetry, and core records from ODP drilling sites, reveal the history of glacial sedimenttransport and deposition since the early Pliocene times. Seismic facies are interpreted in terms of episodes ofslope progradation, contourite, turbidite, trough-mouth fan, and mass transport deposition. Two seismic unitswith estimated age of early to late Pliocene and late Pliocene to recent have been analyzed in detail for the areaimmediately offshore the Lambert Glacier and Prydz Bay and the adjacent Mac. Robertson margin. The upperslope is dominated by episodic mass transport deposits, many of which accumulated to form a trough mouth fansince Early Pliocene times. The trough mouth fan contrasts with the adjacent steep (4–6°) continental slope of theMac. Robertson margin, where glacigenic sediments have been transported down slope as high-velocity turbiditycurrents via submarine channels. The distal region exhibits evidence for contrasting effects of high-energy,traction-dominated versus lower-energy, fallout-dominated suspension flows. The counter-clockwise Coriolisforce modifies the erosion and deposition patterns of turbidity currents creating an asymmetric channel-leveearchitecture. Since the early Pliocene, turbidite sedimentation surpassed the amount of sediment reworked andtransported by westward-flowing contour currents along the base of slope. On the continental rise, contouritesand sediment waves were deposited in response to enhanced bottom-water formation, which is consistent withclimatic cooling since late Pliocene times. This study, based on existing seismic reflection and ODP data,highlights the need for a future scientific ocean drilling proposal on the Prydz Bay continental slope and rise inorder to more accurately determine the timing of the important events that have influenced the evolution of thismargin.