Abstract

Mapping a Cretaceous, island-arc, sedimentary basin revealed a northerly trending submarine canyon complex 4.5 km long and 2 km wide at its southern end. It widens to 4 km in the north, in a downslope direction. The canyon complex cuts across regional stratigraphy and is incised as much as 500 m into a shelf sequence of thinly bedded shale and reef-type limestone. The canyon fill consists of massive, unbedded, mafic, volcanic conglomerate (Tom Spring Formation) and an underlying sequence of volcaniclastic sandstone, calcarenite, shale, and minor conglomerate (Georgia Complex) that was penecontemporaneously deformed.

Structures of the Georgia complex suggest a range of deformation mechanisms, including rigid body rotation of bedded blocks, folding, and mass flow. The variation in structural style is attributed to primary variability in rheological properties and to geometry of the basin floor. The deformation of the Georgia complex is attributed to the catastrophic emplacement of the overlying Tom Spring volcanic conglomerate and to gravity-driven processes within the submarine canyon.

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