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Sedimentology, stratigraphic architecture and depositional context of submarine frontal-lobe complexes

Emma A. Morris, David M. Hodgson, Stephen S. Flint, Rufus L. Brunt, Peter J. Butterworth and Jona Verhaeghe
Sedimentology, stratigraphic architecture and depositional context of submarine frontal-lobe complexes
Journal of Sedimentary Research (September 2014) 84 (9): 763-780

Abstract

Frontal lobes develop during discrete periods of progradation in deep-water systems, and commonly form on the lower slope to base of slope. In reflection seismic datasets, they are identified as high-amplitude reflectors that are cut as the feeder channel lengthens. Here, an exhumed sand-prone succession (> 80% sandstone) from Sub-unit C3 of the Permian Fort Brown Formation, Laingsburg depocenter, Karoo Basin, South Africa, is interpreted as a frontal-lobe complex, constrained by its sedimentology, geometry, and stratigraphic context. Sub-unit C3 crops out as a series of sand-prone wedges. Individual beds can be followed for up to 700 m as they thin, fine, and downlap onto the underlying mudstone. The downlap pattern, absence of major erosion surfaces or truncation, and constant thickness of underlying units indicates that the wedges are non-erosional depositional bodies. Their low aspect ratio and mounded geometry contrasts markedly with architecture of terminal lobes on the basin floor. Furthermore their sedimentology is dominated by decimeter-scale sinusoidal stoss-side preserved bedforms with a range of low-angle to high-angle climbing-ripple laminated fine-grained sandstones. This indicates that the flows deposited their load rapidly close to, and downstream from, an abrupt decrease in confinement. The sedimentology, stratigraphy, cross-sectional geometry, and weakly confined setting of a sand-prone system from the Giza Field, Nile Delta, is considered a close subsurface analogue, and their shared characteristics are used to establish diagnostic criteria for the identification and prediction of frontal-lobe deposits. In addition, deposits with similar facies characteristics have been found at the bases of large external levee deposits in the Fort Brown Formation (Unit D). This could support models in which frontal lobes form an initial depositional template above which external levees build, which provides further insight into the initiation and evolution of submarine channels.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 84
Serial Issue: 9
Title: Sedimentology, stratigraphic architecture and depositional context of submarine frontal-lobe complexes
Affiliation: University of Liverpool, School of Environmental Science, Liverpool, United Kingdom
Pages: 763-780
Published: 201409
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 92
Accession Number: 2014-082892
Categories: StratigraphySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., sketch maps
S33°12'00" - S33°12'00", E20°51'00" - E20°51'00"
Secondary Affiliation: University of Leeds, GBR, United KingdomUniversity of Manchester, GBR, United KingdomBP Egypt, EGY, EgyptBP Angola, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201443
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