--> --> Abstract: Architectural Variability of Turbidite Systems within a Prograding Basin Slope Succession: Laingsburg Formation, Karoo Basin, South Africa, by Martin Grecula, Stephen S. Flint, and Henry DeV. Wickens; #90914(2000)

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Martin Grecula1, Stephen S. Flint1, Henry DeV. Wickens2
(1) University of Liverpool, Liverpool, United Kingdom
(2) University of Stellenbosch, South Africa

Abstract: Architectural variability of turbidite systems within a prograding basin slope succession: Laingsburg Formation, Karoo Basin, South Africa

The Laingsburg Formation represents the period of sand-rich turbidite deposition in the Permian deep-water fill of the Karoo foreland basin. A well exposed 800 m thick succession comprising six turbidite fans, A-F, is a record of the gradual basin floor to slope progradation. Detailed reconstruction of fans B-F, based on extensive field measurements and photostratigraphy, enabled the identification of variability and specific trends in the character and geometry of architectural elements in the successive slope turbidite systems. Fan B, interpreted as a base-of-slope deposit, is a very persistent, up to 220 m thick sand-rich system. Depositional type channel complexes (1-4 km wide and 20-80 m thick) with amalgamated thick-bedded fill dominate its stratigraphy. There is only subtle levee morphology present and most of the channel-fill layers pass laterally into thin-bedded "overbank" sandstones, stretching up to 10 km either side of the channel zone. Downdip, transitional channel-sheet geometries reflect relatively unconfined deposition in the proximal lobe setting. Overlying fans C-F are highly discontinuous, much thinner than Fan B and display higher degrees of lateral variability. More types, including highly erosional channels with different aspect ratios and style of the fill are present as well as extensive slump horizons. Fan complexes C-F pinch out more proximally than fans A and B, and are interpreted to represent a reduced sediment supply filling subtle intraslope basins. Various possible controls on the observed depositional styles are discussed in order to assess predictability of the character of turbidite systems in a slope setting.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana