Abstract

Three boreholes, ten vibrocores, and high-resolution seismic reflection records were analyzed to reconstruct the stratigraphy of the topmost 50 m of the sedimentary column of southwest Sable Island Bank. The sequence is complex owing to the effects of two low stands of sea level, two periods of ice influence, and two periods of open water during the past 40,000 yr. A low stand at -98 m occurred at 28,000 to 32,000 yr B.P.; a second low stand occurred at -110 m between 13,000 and 15,000 yr B.P. Ice covered the region prior to 32,000 yr B.P. and from 11,000 to 10,000 yr B.P. Open water prevailed at other times. The sequence of sediments follows the formational subdivision of King and the member subdivision of Amos and Knoll. The Sable Island Sand and Gravel Formation is subdivided into three members: trough-bedded sand, cross-bedded sand, and conformably bedded sand. The conformably bedded sand formed under heavy sea ice and represents the Younger Dryas event. The uppermost two members result from shelf sediment reworking. The Emerald Silt Formation is subdivided into four members: channel gravel, upper stratified sand/fines, barren gravelly/sand, and lower stratified sand/fines and two regional discontinuities, R1 and R2. The coarser-grained facies of the channel gravel and barren gravelly/sand members are the result of reworking during late and mid-Wisconsinan transgressions of Sable Island Bank. The upper stratified sand/fines member is interpreted as an open-water marine deposit formed during the Scotian Stade. The lower stratified sand/fines member is interpreted as a glacio-marine deposit formed during the Digby Stade.

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