Sedimentary processes in submarine canyons

Abstract

Submarine canyons are one of the most dramatic morphological features on continental margins and enable sediment transport from the shelf to the deep sea; however, the exact processes operating within submarine canyons are poorly understood. Much of our understanding of the dynamics of sediment-laden flows in submarine canyons results from making inferences from the deposits that they leave behind in the geological record.
This thesis aimed to better understand what deposits can reveal about flow processes and ultimately to test the validity of this approach for reconstructing flow dynamics. This aim was achieved by 1) analysing seafloor bedforms, 2) the detailed lithological and ichnological analysis of submarine canyon deposits, and 3) utilising turbidity current monitoring data. Construction and analysis of a global database of seafloor bedforms suggests that bedforms across all scales and a wide variety of settings can be generated by supercritical flows. The most complete dataset of monitored turbidity currents in a submarine canyon was combined with precisely located vibracores collected in Monterey Canyon. The combination of these datasets demonstrates that deposits can be used to accurately infer flow properties, and the data were further used to develop a new three-part model for turbidity current behaviour: 1) flows begin as thin, high-concentration highly energetic flows; 2) the flows become more dilute with an expanding head; and 3) the flow rapidly thickens along its length. This new model of turbidity current behaviour, along with understanding the frequency of these events, explains the distribution of benthic communities in Monterey Canyon based on the biogenic sedimentary structures identified within the sedimentary cores.

More information

Identifiers

Catalogue record

Export record