Unconfined gravity current interactions with orthogonal topography: Implications for combined‐flow processes and the depositional record

Keavney, Ed; Peakall, Jeff; Wang, Ru; Hodgson, David M.; Kane, Ian A.; Keevil, Gareth M.; Brown, Helena C.; Clare, Michael A. ORCID: https://orcid.org/0000-0003-1448-3878; Hughes, Mia J.. 2024 Unconfined gravity current interactions with orthogonal topography: Implications for combined‐flow processes and the depositional record. Sedimentology. https://doi.org/10.1111/sed.13227

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Text Ó 2024 The Author(s). Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologists. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Sedimentology - 2024 - Keavney - Unconfined gravity current interactions with orthogonal topography Implications for.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (6MB) | Preview

Abstract/Summary

Turbidity current behaviour is affected by interactions with seafloor topography. Changes in flow dynamics will depend on the orientation and gradient of the topography, and the magnitude and rheology of the incoming flow. A better understanding of how unconfined turbidity currents interact with topography will improve interpretations of the stratigraphic record, and is addressed herein using three-dimensional flume tank experiments with unconfined saline density currents that enter a horizontal basin before interacting with a ramp orientated perpendicular to flow direction. The incoming flow parameters remained constant, whilst the slope angle was independently varied. On a 20° slope, superelevation of the flow and flow stripping of the upper, dilute region of the flow occurred high on the slope surface. This resulted in a strongly divergent flow and the generation of complex multidirectional flows (i.e. combined flows). The superelevation and extent of flow stripping decreased as the slope angle increased. At 30° and 40°, flow reflection and deflection, respectively, are the dominant flow process at the base of slope, with the reflected or deflected flow interacting with the parental flow, and generating combined flows. Thus, complicated patterns of flow direction and behaviour are documented even on encountering simple, planar topographies orientated perpendicular to flow direction. Combined flows in deep-water settings have been linked to the interaction of turbidity currents with topography and the formation of internal waves with a dominant oscillatory flow component. Here, combined flow occurs in the absence of an oscillatory component. A new process model for the formation and distribution of hummock-like bedforms in deep-marine systems is introduced. This bedform model is coupled to a new understanding of the mechanics of onlap styles (draping versus abrupt pinchout) to produce a spatial model of gravity-current interaction, and deposition, on slopes to support palaeogeographical reconstructions.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1111/sed.13227
ISSN:	0037-0746
Additional Keywords:	Combined flows, flow confinement, flume experiments, hummocky bedforms, low-density turbidity currents, onlap styles, orthogonal topography
Date made live:	05 Sep 2024 15:58 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537971

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