Reversing buoyancy in turbidity currents: developing a hypothesis for flow transformation and for deposit facies and architecture

Pritchard, David and Gladstone, Charlotte (2009) Reversing buoyancy in turbidity currents: developing a hypothesis for flow transformation and for deposit facies and architecture. Marine and Petroleum Geology, 26 (10). pp. 1997-2010. DOI 10.1016/j.marpetgeo.2009.02.010

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Abstract

A turbidity current that contains fresher or otherwise less dense water than its surroundings may initially be denser than the ambient and propagate as a bottom-hugging flow, but later reverse in buoyancy as its bulk density decreases through sedimentation to become lower than that of the ambient seawater. It is proposed that this reversal in buoyancy may be a significant mechanism controlling the structure and facies of turbiditic deposits. Buoyancy reversal followed by lofting may directly affect the relative distribution of fine and coarse material in the deposit, while buoyancy reversal itself may mediate the transformation between dilute and highly-concentrated suspension flows, particularly in distal regions, and thus lead to the formation of complex turbiditic beds: in particular, the generation of distal co-genetic debrites may be expected. Similar transformations occur within dilute pyroclastic density currents, where a mobile, basal concentrated flow, termed a surge-derived pyroclastic flow, develops through rapid sedimentation from the suspended load of the overlying surge. The physical mechanisms involved in these processes are discussed, leading to the proposal of some associated facies models; these are compared with field data from the Northern Apennines, with some striking similarities being noted as well as some differences. On the basis of this discussion, some directions are suggested for future experimental and modelling work on the topic.

Item Type: Article
Uncontrolled Keywords: 09AREP; IA59;
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title: Marine and Petroleum Geology
Volume: 26
Page Range: pp. 1997-2010
Identification Number: 10.1016/j.marpetgeo.2009.02.010
Depositing User: Sarah Humbert
Date Deposited: 22 Mar 2010 13:38
Last Modified: 23 Jul 2013 09:56
URI: http://eprints.esc.cam.ac.uk/id/eprint/1347

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