Modelling the architecture of distal sand-rich lobe deposits : an example from Fan 2, Skoorsteenberg Formation, Tanqua Karoo, South Africa
Date
2009-03
Authors
Steyn, Rochelle
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Fan 2, one of five submarine fan systems of the Tanqua fan complex in the
south-western Karoo Basin, South Africa, is subdivided into Lower, Middle
and Upper units. Here, detailed analysis of the internal architecture and
distribution of lithofacies associations of Middle Fan 2 facilitated the 3-D
visualisation of the sedimentological and stratigraphical changes towards the
pinch-out.
Middle Fan 2 is interpreted to be a lower-fan, sand-rich terminal lobe,
comprising three sandstone-lobe elements, separated by two siltstone interlobe
elements. It is fed by a distributary channel that is hypothetically
positioned to the west-southwest of the study area. The sandstone-lobe
elements pinch out downdip to the north-east and updip to the southsouthwest
in the study area. The consecutive pinch out of lobe elements to
the north-east indicates a progradational stacking pattern similar to the entire
lobe complex.
Palaeocurrent analysis and the interpretation of isopach maps indicate that
the transport direction of Middle Fan 2 was in a north-easterly direction. The
fringes of the lobe and the distribution of internal elements (channels,
amalgamated sheets and sheets) show a finger-like geometry in plan-view, in
contrast to simple radial-lobe bodies that are commonly envisaged.
Description
MSc
Thesis (MSc (Earth Sciences))—University of Stellenbosch, 2009.
Thesis (MSc (Earth Sciences))—University of Stellenbosch, 2009.
Keywords
Tanqua Karoo, Co-genetic debrites, Middle Fan 2, Dissertations -- Geology, Theses -- Geology