Facies architecture of individual basin-plain turbidites: Comparison with existing models and implications for flow processes

Sumner, Esther J., Talling, Peter J., Amy, Lawrence A., Wynn, Russell B., Stevenson, Christopher J. and Frenz, Michael (2012) Facies architecture of individual basin-plain turbidites: Comparison with existing models and implications for flow processes. Sedimentology, 59, (6), 1850-1887. (doi:10.1111/j.1365-3091.2012.01329.x).


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Current understanding of submarine sediment density flows is based heavily on their deposits, because such flows are notoriously difficult to monitor directly. However, it is rarely possible to trace the facies architecture of individual deposits over significant distances. Instead, bed-scale facies models that infer the architecture of ‘typical’ deposits encapsulate current understanding of depositional processes and flow evolution. In this study, the distribution of facies in 12 individual beds has been documented along downstream transects over distances in excess of 100 km. These deposits were emplaced in relatively flat basin-plain settings in the Miocene Marnoso Arenacea Formation, north-east Italy and the late Quaternary Agadir Basin, offshore Morocco. Statistical analysis shows that the most common series of vertical facies transitions broadly resembles established facies models. However, mapping of individual beds shows that they commonly deviate from generalized models in several important ways that include: (i) the abundance of parallel laminated sand, suggesting deposition of this facies from both high-density and low-density turbidity current; (ii) three distinctly different types of grain-size break, suggesting waxing flow, erosional hiatuses and bypass of silty sediment; (iii) the presence of mud-rich debrites demonstrating hybrid flow deposition; and (iv) dune-scale cross-lamination in fine-medium grained sandstones. Submarine sediment density flows in basin-plain settings flow over relatively simple topography. Yet, their deposits record complex flow events, involving transformation between different flow types, rather than the simple waning surges often associated with the distal parts of turbidite systems.

Item Type: Article
Digital Object Identifier (DOI): doi:10.1111/j.1365-3091.2012.01329.x
ISSNs: 1469-3496 (print)
1365-3091 (electronic)
Keywords: Marnoso Arenacea Formation; Agadir Basin; turbidity current; debris flow; sedimentary structures
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Q Science > QE Geology
Divisions : National Oceanography Centre (NERC) > Marine Geoscience
Faculty of Natural and Environmental Sciences > Ocean and Earth Science > Geology & Geophysics
ePrint ID: 340160
Accepted Date and Publication Date:
2012In press
October 2012Published
Date Deposited: 13 Jun 2012 13:05
Last Modified: 31 Mar 2016 14:29
URI: http://eprints.soton.ac.uk/id/eprint/340160

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