Abstract

Seismic surveys of the glacial and proglacial sediments of Emerald Basin show a systematic succession representing one complete cycle of deglaciation. The succession consists of a thin layer of acoustically incoherent sediments overlain by a thick sequence of acoustically stratified muds, capped by ponded, acoustically transparent Holocene sediments. The incoherent sediments, interpreted as a subglacial till, extend across the basin. The stratified proglacial sediments contain five erosional or nondepositional surfaces, thought to be of chronostratigraphic significance. These five surfaces are used to divide the proglacial sediments into lithosomes, each of which is influenced to varying degrees by three depositional mechanisms: suspension rain-out, ice rafting, and turbidity currents.Radiocarbon dating indicates that deglaciation started at about 18 ka. Although the main ice sheet retreated landward, deglaciation was locally complex, and a series of ice rises likely persisted until about 12 ka, grounded on the banks of the outer and central Scotian Shelf. Retreat of ice from the Scotian Shelf is recorded as a reduction of sedimentation rates, a decrease in the amount of coarse (> 500 μm) clasts supplied to the basin, the absence of iceberg scours in the upper sediments of the basin, and the disappearance of depocentres of proglacial sediments from the southern and eastern flanks of the basin by 11 ka.

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