Downslope sediment transport processes and sediment distributions at the East Breaks, Northwest Gulf of Mexico




Piper, James Nolan

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High-frequency 3.5-kHz acoustic reflection data and piston cores collected during 19 research and student-training cruises were used to interpret sediment distribution and downslope sediment transport processes involved in the formation of the two lobes of the East Breaks slide. The distribution of depositional systems was mapped by developing an acoustic facies classification system from 28,000 kms of high-resolution 3.5-kHz acoustic reflection data. Bathymetry and piston core data were also used in interpretations. Fourteen acoustic facies were recognized. Previous investigations of the near-surface geomorphology of the East Breaks slide interpreted this site as having been formed by a single mass-wasting event at the terminous of a late Wisconsinan shelf-edge delta. According to these interpretations, after initiation, this slide/slump propagated downslope and divided into two major lobes as it encountered a salt diapir-induced bathymetric high. This study shows that the two lobes are genetically separate. The formation involved the two major types of downslope sediment transport mechanisms that dominate the northern Gulf of Mexico: gravity-driven slide/slump/debris flows and turbidity currents. The upper part of the western lobe was produced by mass wasting, and the eastern lobe was formed by channelized turbidity currents