Fine-grained, Submarine-fan Growth and the Distribution of Lithofacies and Architectural Elements: An Example (Fan 4) from the Skoorsteenberg Formation Basin, South Africa
David M Hodgson, Nicholas J Drinkwater, Stephen S Flint, Stefan M Luthi, David Hodgetts, Erik P. Johannessen, H. De Ville Wickens, Kevin J. Keogh, John P. Kavanagh, John A. Howell, 2008. "Fine-grained, Submarine-fan Growth and the Distribution of Lithofacies and Architectural Elements: An Example (Fan 4) from the Skoorsteenberg Formation Basin, South Africa", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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The Permian Skoorsteenberg Formation in the Tanqua depocenter, southwest Karoo basin, South Africa, provides outstanding exposures of four sand-rich, basin-floor fans (Figure 1). The integration of correlated outcrops and recently acquired conventional cores and wireline logs, an extensive paleocurrent dataset, and accurate GPS-mapped fan surfaces has enabled robust models of the stratigraphic evolution of the fan systems to be developed. This paper focuses on a reinterpretation of the stratigraphic organization and evolution of Fan 4, the youngest basin-floor fan, and documents the distribution of architectural elements (Panels A-D) within a generic stratigraphic framework. Proximal feeder systems display an upward increase in the depth of incision, with thicker accumulations of mudstone-clast conglomerates (Panel A). Basinward, the axial parts of the fans during progradational and aggradational phases are dominated by amalgamated sheet turbidites (Panels B and D). In particular, an architectural element, which does not fit into the commonly used channel or sheet classification scheme, is referred to as a highly amalgamated sheet-turbidite zone (Panel C). Mapping of high-frequency intrafan sequences reveals a progradational-aggradational-retrogradational stacking pattern within each submarine fan, which enables the geographic and stratigraphic distribution of lithofacies and architectural elements to be reasonably predicted. The progradational, aggradational, and retrogradational phases are assigned to the early, middle, and late lowstand system tracts, respectively, of a fifth-order sequence. Each phase is built of higher frequency sequences, so that each fan is a composite sequence. The fine-grained, submarine-fan systems of the Tanqua depocenter lose section and reservoir sandstones from the base (through progradation)
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Tor H. Nilsen, a red-haired Scandinavian who stood more than six feet tall, died October 9, 2005, at his San Carlos, California, home. This was after a valiant five-year fight with melanoma cancer. He was 63. His ashes were scattered at his family plot in Norway in 2006.
He was born in New York City on November 29, 1941, to Mollie Abrahamson and Nils Marius Nilsen of Mandal, Norway, and was the first of their children to be born in the United States. After graduating from Brooklyn Tech, he earned his B.S. in geology from City College of New York in 1962. While there, his prowess on the basketball court impressed a scout from the New York Knicks, but Tor went on to graduate school and earned his M.S. and Ph.D. degrees in geology from the University of Wisconsin at Madison in 1964 and 1967, respectively. His M.S. thesis was a study of Precambrian metasedimentary deposits in the Lake Superior area, and his Ph.D. thesis was a study of Devonian alluvial-fan deposits of the Old Red Sandstone in western Norway.
Dr. Nilsen’s principal expertise was in depositional systems analysis, stratigraphic analysis, and the relationships among tectonics, eustasy, and sedimentation. He began his industry career in 1967 as a research geologist with the Shell Development Company in Houston, Texas, and Ventura, California, where he worked on the tectonics and sedimentation of Tertiary shelf systems of coastal California. He subsequently spent two years with the U.S. Army Corps of Engineers as the Military