Miocene changes in bottom current regime recorded in continental rise sediments on the Pacific Margin of the Antarctic Peninsula

A Fossil Mounded Sedimentary Body (MB) has been identified in the Miocene sedimentary record on the central continental rise west of Adelaide Island, Antarctic Peninsula, using multichannel seismic reflection profiles. The MB has an elongated NE trend away from a group of seamounts, and it developed between two troughs. We interpret it as a patch drift plastered against the NE (lee) side of an obstacle. The MB's depositional patterns provide the first clear evidence of Early Miocene bottom current activity on the central rise, and they suggest that flow was towards the NE, probably as part of the Antarctic Circumpolar Current. This segment of the rise is, however, presently affected by a SW-flowing branch of Lower Circumpolar Deep Water. The change in bottom water flow took place during the Middle or Late Miocene, and we suggest that it is probably indicative of more widespread palaeoceanographic changes during this period.