Sedimentation from forced wall jets versus free gravity flows: integrating tank experiments and field data into a physics-based depositional model

• Applicant: Dr. Jörg Lang
• Subject Area: Palaeontology
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 407609989

Recently, the impact of Froude supercritical density flows on deepwater clastic depositional systems has been increasingly recognized. These deposits are mainly preserved in the regions of expanding flows, where the aggradation is highest. Such regions of expanding flow can be modeled as supercritical jet flows. Submerged plane-wall jet flows, which emerge from an orifice into a standing water body and decelerate, can be considered as basic model for depositional processes related to expanding, point-sourced flows, like submarine fans and subaqueous ice-contact fans. The morphodynamics of expanding supercritical flows have a large impact on the dispersal of sediment and the resulting depositional architecture of subaqueous ice-contact fans, deposited by jet flows, and submarine fans, deposited by gravity flows, respectively. Jet flows and their deposits display a distinctive proximal to distal zonation. The densimetric Froude number exerts a primary control on the flow dynamics and the evolution from inertia-driven jets into density-driven gravity flows. The transition between plane-wall jets and gravity flows has a large impact on the deposition by expanding flows. The existing knowledge of jet flows and gravity flows, their hydrodynamic and morphodynamic evolution, and their deposits is insufficient to explain the characteristic bedform and facies successions. This project is designed to investigate these two flow types and develop recognition criteria for their deposits by integrating observations from tank experiments and field data. In the experimental part of the project, the morphodynamics of jet flows and gravity flows will be characterized in tank experiments, enabling the systematic variation of the controlling flow and sediment parameters. In the field part of the project, deposits related to zones of flow expansion from coarse-grained supercritical submarine fans will be studied. These field examples must enable a detailed characterization of the depositional architecture and facies successions and provide sufficient detail to invert for flow forcing. By the integration of the observations from the experiments and the outcrops a generic, physics-based model for deposition by expanding supercritical density flows will be developed.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Dr. David Hoyal