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A Lower Cretaceous clastic slope succession, Livingston Island, Antarctica: sand-body characteristics, depositional processes and implications for slope apron depositional models

Lomas, Simon A.. 1999 A Lower Cretaceous clastic slope succession, Livingston Island, Antarctica: sand-body characteristics, depositional processes and implications for slope apron depositional models. Sedimentology, 46 (3). 477-504. 10.1046/j.1365-3091.1999.00225.x

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Abstract/Summary

The early Cretaceous fill of the forearc/intra-arc Byers Basin includes a 600- to 900-m-thick interval of marine slope apron deposits, the President Beaches Formation. This is a predominantly argillaceous succession within which coarser-grained deposits are largely confined to lenticular packages of low width–thickness ratios. The entire formation was deposited in mid- to late-Berriasian times, coincident with a pulse of regional arc expansion, at minimum mean accumulation rates of 120–225 mm 1000 years–1. The mudstones are finely laminated, with a restricted benthic macrofauna and minimal bioturbation, indicating relatively inhospitable sea-floor environments. Sand-rich packages occur as 7- to 30-m-thick channel-fill units composed chiefly of classical medium-grained turbidites, in some cases associated with complex high-concentration turbidity current deposits and minor mud-rich debrites. These sand-bodies are apparently elongate along (normal to) the NW-facing palaeoslope implied by slump-fold axes (and the strike of the volcanic arc). Similarly, palaeocurrent indices show a consistent arc-parallel, NE-directed trend, suggesting that transport processes were strongly influenced by the structural ‘grain’ of the irregular slope morphology. Slope instability is recorded by widespread slump and soft-sediment collapse features promoted by a combination of steep sea-floor gradients and relatively high rates of sedimentation. A lack of systematic vertical facies trends indicates that this was not a progradational or well-organized system, despite high rates of sediment supply. However, the strong systematic relationship between palaeocurrents and palaeoslope suggests a promising basis for evaluating organization in otherwise poorly ordered slope apron depositional systems.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1046/j.1365-3091.1999.00225.x
Programmes: BAS Programmes > Pre 2000 programme
ISSN: 0037-0746
Additional Keywords: Byers Peninsula, palaeocurrents, slope apron, slope channels, slumps, turbidites
Date made live: 21 Oct 2013 10:08 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/503576

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