Abstract

Grain-size distribution reveals three detrital sedimentary deposits: an outer-shelf sand deposit (1.5-3.0 phi , well sorted, negatively skewed); an inner-shelf mud deposit (6-9 phi , poorly sorted, positively skewed); and a corridor extending from the river mouth across the inner shelf, in which mud is interbedded with sand. Modern mud covers most of the inner shelf, and surface sediment does not reveal along-shelf or across-shelf sorting of discrete particles. A lack of shoreward fining contradicts the sedimentation model of Gibbs (1976). The model most consistent with observations is a modern subaqueous delta prograding over a relict basal sand (the outer-shelf sand). Modern sand in surface sediment is restricted to the corridor extending from the river mouth across the inner shelf. Ambient processes are not competent to transport this sand along-shelf. Subsurface sand layers within the inner shelf mud deposit (i.e., outside the corridor) are similar in texture to surficial sand in the corridor of interbedded mud and sand. These observations may suggest that the location and/or size of the corridor has changed with time.--Modified journal abstract.

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