QUATERNARY SEDIMENTARY PROCESSES AND BUDGETS IN ORPHAN BASIN, SOUTHWESTERN LABRADOR-SEA

The continental slope in Orphan Basin, northeast of Newfoundland, is u nderlain by several seaward-thinning debris-how wedges alternating wit h acoustically stratified, regionally extensive, mainly hemipelagic se diments, delta(18)O stratigraphy and volcanic ash layers in a 11.67-m core indicate that the uppermost debris-flow wedge formed during the l ast of several sea-level lowstands in isotopic stages 2-4. Similarly, seismic reflection correlation of dated levels at DSDP Site 111 with t he Orphan Basin succession suggests that two deeper debris-flow wedges were deposited during oxygen isotopic stages 6 and 8. The oldest of t he debris-flow deposits in at least three of the wedges formed well in to the corresponding glacial cycle, after ice sheets had reached the e dge of the continental shelf, Slower deposition by hemipelagic process es and ice rafting formed the acoustically stratified units, including Hein-rich layers, The youngest three debris-how wedges each have volu mes of 1300-1650 km(3). Approximately two-thirds of this material is a ttributed to glacial erosion of Mesozoic and Tertiary strata beneath t he Northeast Newfoundland Shelf The remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of Newfoundland, The observed sediment volumes and the inferred basal and upper ages of the debris-how wedges imply an average glacial denu dation rate of about 0.13 mm/yr for this older bedrock, and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 2 2. This denudation rate is similar to estimates from the Barents Sea r egion off Norway. (C) 1996 University of Washington.