ABSTRACT: Origin and variability of sedimentary facies of the Fraser River delta foreslope, British Columbia

CGRG Bibliography of Canadian Geomorphology
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Abstract

Five sedimentary facies have been recognized in piston cores from the Fraser River delta foreslope: (1) river plume suspension deposited massive silty clay with minor organics, (2) suspension deposited silty clay to clayey silt with rare parallel silt and very fine sand laminations deposited under minor traction, (3) clayey silt with silt or very fine sand interbeds from mixed suspension and low density turbidity current traction deposition, (4) silty, very fine to medium-grained sand with less than 10% thin clay or silt interbeds, predominantly deposited from high density turbidity currents, and (5) organic-rich, disorganized, chaotic beds. Facies distribution patterns suggest that the Fraser Delta foreslope is dissected by a number of both active and inactive channels. These channels have served as a mechanism for coarse-grained sediment to bypass the delta plain and upper foreslope and be introduced directly to the lower foreslope and basin floor. It is hypothesized that these channels debouch as a series of depositional lobes and slump-related failure deposits in the prodelta/basinal environment. The direct introduction of clastic sediment into water depths exceeding 250 m suggests a process analogue for the interpretation of shelf-edge deltas in the rock record. Thus, the Fraser River delta may offer a unique opportunity to model active sedimentation associated with a lowstand of sea level.

Bibliography of Canadian Geomorphology