An integrated investigation of Froude-supercritical turbidity current dynamics and products in deep-water slope systems
Deep-water settings represent one of the most poorly understood sedimentary environments, largely due to a lack of direct observations from modern systems. Technological advancements have recently enabled high-resolution seafloor mapping and water column monitoring that have incited interest in supercritical (Froude number >1) flow dynamics. Inspired by novel seafloor findings, this doctoral research applies an integrated approach to investigate the occurrence and depositional products of Froude-supercritical turbidity currents in sandy submarine slope channels and intraslope lobes. It uses a combination of numerical (computational fluid dynamic models), modern (repeat bathymetry from the Squamish prodelta, Canada, and Monterey Canyon, USA), and ancient (outcrop characterization from the Nanaimo Group, Canada, and Tres Pasos Formation, Chile) datasets to elucidate turbidity current bedform development and downslope flow evolution in these settings. Numerical simulations reveal the morphodynamic processes associated with decameter-scale upstream-migrating bedforms, comparable to those commonly observed in sandy submarine slope channels and lobes on the seafloor. Results confirm that these bedforms are formed by Froude-supercritical turbidity currents with denser basal layers and can be classified as upper-flow-regime bedforms called cyclic steps. Three-dimensional architectural characterization of modern and ancient strata demonstrate that cyclic step migration produces backstepping asymmetric lenses, which are meters to tens of meters long and <1 m thick. Bedform distribution on the seafloor and the identification of analogous lenses in outcropping slope strata provide insight into the downstream evolution of flows and influence of topographic features. Collectively, the results in this thesis support the ubiquitous importance of Froude-supercritical conditions in turbidity current sediment transport across a range of depths and positions on deep-water slopes. Incorporation of new modern datasets provide robust support for the establishment of process-to-product relationships, previously lacking in deep-water sedimentological investigations. This research contributes to the understanding of flow processes associated with bedforms and topographic interactions, which is important for predicting modern turbidity current hazards where similar features occur on the seafloor. As well, it informs paleoenvironmental interpretations of sedimentary structures in ancient deep-water successions that hold critical records of events in Earth history.
Englert, R. G. (2022). An integrated investigation of Froude-supercritical turbidity current dynamics and products in deep-water slope systems (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.