A Late Quaternary canyon/channel system, northwest Gulf of Mexico continental slope

Abstract

A late Quaternary submarine canyon and channel system, mapped on the north-west slope (long. 94–95°W) of the Gulf of Mexico with high-resolution (3.5 kHz) seismic reflection profiling and sidescan sonar, can be divided into two types of units: (1) leveed, aggradational, intrabasinal channels which cross intraslope basins on the upper slope, and (2) erosional interbasinal canyons which connect the intraslope basins. A main valley crosses three filled sedimentary basins on the upper slope and ends in a midslope, silled bathymetric basin. This suggests a scenario of successive downslope basin filling by channelized turbidity currents. However, turbidites occur farther downslope without a known submarine valley delivery system. Preservation quality of the system decreases downslope into fragmented canyon/channel remnants on the mid-lower slope. This trend is believed to be controlled by distance from sediment source and magnitude of salt tectonism. It is surmised that during lowstands and the initial rises in sea level, a continuous downslope canyon/channel network might have been active but subsequently deteriorated from a lack of sediment and increased, relative salt tectonism during sea-level highstands.