Processes on sediment drifts from 3.5 kHz data, Antarctic Peninsula continental rise
On the continental rise west of the Antarctic Peninsula, large sediment drifts preserve a hihg-resolution record of Neogene glaciation, We present a new map of acoustic facies on the continental rise, derived from 3.5 kHz profiles. Most drifts have steep sides to the southeast (towards the base of the slope) and southwest (towards the channels which separate each drift). The gentle slopes of the drifts (to northeast, and merging with the abyssal plain to the northwest) contain laterally continuous sub-bottom reflectors. Convergence of reflectors to the northwest shows the sediments thin offshore, confirmed by core studies; strike lines show negligible thickness change acress the drifts, except within a few kilometres of the channels. It is likely that deposition from meltwater plumes and slope-derived turbidity currents pevailed over deposition from channelised turbidity currents. Small areas of sediment waves occur on two drifts. Evidence for small-scale mass wasting includes normal faults and slump blocks on the steep sides of all the the drifts, and one drift contains a number of small, locally derived debris flows. Both 3.5 kHz profiles and cores show evidence for a change in sedimentation style at c. 3300 m water depth, with intermittent bottom-current winnowing above this depth. Sedimentation rates from ODP Leg 178 show the acoustic penetration depth of some 50 m represents the last 0.5-1.0 m.y. of deposition.
Authors: Pudsey, Carol J., Howe, John A., Morris, Peter, Gunn, David E.
Editors: Gamble, J.A., Skinner, D.N.B., Henry, S.
1 January, 2002
In: Gamble, J.A., Skinner, D.N.B., Henry, S. (eds.). Antarctica at the close of a millennium. Proceedings of the 8th International Symposium on Antarctic Earth Sciences, Wellington, 1999, Wellington, The Royal Society of New Zealand, 345-350.