Late Tertiary sediment basin on continental slope off Western Nova Scotia

The continental slope off Nova Scotia was shaped during the Cenozoic by progradation, erosion, and intrusion by salt-cored diapirs termed the Sedimentary ridge. No evidence has previously been reported that Cenozoic sediment accumulation on the slope landward of the sedimentary ridge was affected by sea-floor deformation owing to growth of diapirs. As part of a regional survey, seismic stratigraphy in reflection profiles shot on the slope between 61/sup 0/ and 64/sup 0/W was tied to wells on the upper slope and shelf. Dip profiles show three reflector sequences, each about 0.5 sec two-way travel time thick, which terminate in a seaward direction against diapirs of the Sedimentary ridge. Whereas reflectors within the upper and lower sequences dip at least 2/sup 0/ seaward, reflectors within the middle sequence lie flat, lap out onto an unconformity postdating the Eocene-Oligocene canyon-cutting event along the Scotian shelf, and are truncated seaward by a sharp Pliocene-Pleistocene(.) unconformity. Neither rotation along listric faults nor back-tilting by uplift in the Sedimentary ridge can account for the geometry and along-strike continuity (200 km) of the middle sequence. It is proposed that sediments forming the flat reflectors were ponded landward of a sea-floor ridge in the present position ofmore » the Sedimentary ridge. The dam was formed in the late Paleogene by sediments uplifted above linear salt ridges. Subsequently, erosion removed both the dam and the outward portion on the ponded sediments, and diapirs rose from the salt ridges.« less