--> ABSTRACT: Utility and Variability of Bed Thickness Stacking Pattern in Submarine Lobes: Examples from the Laingsburg Formation, Karoo Basin, South Africa, by Prelat, Amandine; Hodgson, David; #90142 (2012)
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Utility and Variability of Previous HitBedNext Hit Thickness Stacking Pattern in Submarine Lobes: Examples from the Laingsburg Formation, Karoo Basin, South Africa

Prelat, Amandine *1; Hodgson, David 2
(1) Department of Earth Science & Engineering, Imperial College London, London, United Kingdom.
(2) School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom.

Within small-scale outcrops, core, or well log datasets, thickening upward packages of sandstone beds are often used as a criterion to interpret lobe deposits in submarine fan systems. However, terminal lobe deposits from the Laingsburg depocentre, south west Karoo Basin, demonstrate that a full range of Previous HitbedNext Hit stacking patterns exists within stacked lobes (lobe complexes). The exposures allow accurate measurements of individual Previous HitbedNext Hit thicknesses and therefore an insight into Previous HitbedNext Hit thickness trend at lobe scale. The definition and recognition of lobes is based on the nature of bounding surfaces across which there are abrupt sedimentary facies changes and their lateral extents, rather than on the thickness, dominant lithofacies and Previous HitbedNext Hit thickness trend of the package between these two surfaces. Three outcrop sections through Unit A of the Laingsburg formation were chosen at various localities along the Baviaans syncline (called Krans, Wilgerhout and Buffel) along with a research borehole (BAV 1B). The five end members of Previous HitbedNext Hit stacking patterns recognised and described in this study are named: thickening upward, thinning upward, thickening-then-thinning upward, thinning-then-thickening upward, and constant Previous HitbedNext Hit thickness. Observations show that Previous HitbedNext Hit stacking patterns within a lobe can vary over short distances (<km) and that it is not related to the location of sampling. The Previous HitbedNext Hit stacking pattern of lobes is interpreted to be controlled by the internal organisation of smaller scale components, i.e. individual beds - bedsets and lobe elements, rather than simple widespread and ubiquitous progradation as implied by thickening upward patterns. An understanding of the significance of Previous HitbedTop stacking pattern at lobe scale is crucial to better help recognition and interpretation of individual lobes within poorly exposed outcrops and subsurface dataset.
 

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California