Deep-water Basin-floor and Slope Deposits of the Laingsburg Depocenter, Karoo Basin, South Africa
Stephen Flint, David Hodgson, Peter Sixsmith, Martin Grecula, H. de Ville Wickens, 2008. "Deep-water Basin-floor and Slope Deposits of the Laingsburg Depocenter, Karoo 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 230-m (754-ft)-thick Vischkuil Formation and overlying 850-m (2800-ft)-thick Laingsburg Formation represent the early deep-water phase of retro-arc foreland basin stratigraphy in the Karoo basin, South Africa. Using radiometric dates from ashes and thicknesses of pelagic shale decompacted and compared to modern-day depositional rates, the succession is interpreted as a third-order falling stage (FSST) and lowstand systems tract (LST). The upper Vischkuil Formation comprises a series of large-scale mass-transport complexes (MTCs) that can be correlated more than 20 km (12 mi) downdip. Mapping suggests that emplacement of these features created sea-floor topography, which influenced thickness and facies distribution in the lower part of the overlying basal Laingsburg Formation Fan A complex. The N1 road links Cape Town and Johannesburg. When travelling from the south, 1 km (0.6 mi) before the town of Laingsburg, a series of roadcuts expose the Vischkuil and Laingsburg Formations. The upper MTC is well exposed at the western end of the N1 road cut. The Laingsburg Formation comprises six sandstone-dominated intervals (Fan A and Units B-F), each separated by 10–90 m (33–295 ft) of turbiditic and hemipelagic shales. Fan A is 275 m (907 ft) thick in the road cut and has been divided into seven regionally mappable, high-frequency sequences (growth stages), each comprising a sand-prone lowstand systems tract (15–55 m [49–180 ft] thick) and a mudstone-dominated transgressive/highstand systems tract (5–25 m [16–82 ft] thick). Fan A is therefore a composite sequence. The sandstones in the three lower growth stages are relatively dirty, with the occurrence of occasional floating mudstone clasts,
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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