Model for Submarine Glacial Deposition

Abstract

Present-day sedimentary environments in the eastern Weddell Sea confirm low clastic sediment input from wide (> 100 km) ice shelves. Mainly bioclastic sediments are formed in situ on the inner and shallow central-shelf areas (250 to 350 m water depth), with sedimentation rates probably < 0.01 m ka −3 . Ice-rafted debris (IRD) is mainly deposited on the outer shelf and upper continental slope, with a sedimentation rate of 0.02 to 0.07 m ka −3 . The coarse-grained texture of these deposits is caused by removal of finer grades in suspension during settling of IRD sediments. Overconsolidated till was deposited < 31 ka BP during expansion of grounded ice to the shelf break. Subsequent eustatic rise caused grounded ice to float. Frozen-on sediments melted out of the base of the ice, depositing soft pebbly mud above the till. Marine conditions similar to present-day conditions were found for the interval 30 to 40 ka BP. IRD variation is an indicator of ice-shelf coverage and changes in relative sea-level, and is, in low latitudes, probably inversely related to the degree of ice cover.