Abstract

Outcrops of strata ranging in age from Oligocene to Miocene occur on the sides of The Gully, a large submarine canyon near Sable Island. Data from dredge-sampling operations suggest that the exposed stratigraphic section may be as much as 1400 m thick. Analysis of dredge samples shows that the rocks collected are dominantly mudstone with minor components of sand. The exposed section is slightly coarser and more varied in texture toward the bottom than toward the top. Sand fractions are quartz-rich and contain only minor feldspar and rock fragments. Slight variations in accessory minerals may reflect the relative influences of different source rocks. The mineral suite is generally representative of plutonic and metamorphic source rocks. Abundant pyrite internal molds in mudstones suggested that the Eh in these sediments is negative. Illite and kaolinite composed most of the clay-size fraction of outcrop samples, with lesser amounts of montmorillonite.Continuous-seismic reflection surveys show that sub-bottom reflectors dip gently seaward. Below approximately 600 m, no sub-bottom reflections were recorded. Shallower, more discontinuous reflections suggest that locally reworked beds occur on the rim of the canyon.Petrological, structural, and faunal data indicate that the section is part of the Atlantic Coastal Plain Province, which, prior to this investigation, was known to occur only as far north as Georges Bank.

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