Channel and Levee Deposits, Bloukop Farm, Tanqua Karoo, South Africa
Arnold H Bouma, Anne M Delery, Erik D Scott, 2008. "Channel and Levee Deposits, Bloukop Farm, Tanqua Karoo, 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 Fan 5 outcrops at Bloukop Farm include channel and thin-bed deposits. Initially, this outcrop was interpreted as consisting of middle-fan channel sandstones overlying thin-bedded outer-fan sheet sandstones. Closer examination (and clearing of the outcrop face) revealed that the massive channel sandstones were locally coeval with several of the thin beds (see Figures 4, 5) suggesting channel and levee deposition (Bouma and Wickens, 1994). Kirschner (1999) conducted a detailed study of the area (also reported in Kirschner and Bouma, 2000) that supported this interpretation. Two channels were recognized in the outcrop. channel 1 is the lower channel that shows the connectivity of two of the levee thin beds with the channel sandstones. Most of the other beds are truncated by the channel illustrating variable times of channel cutting and thin-bed deposition. Both of the channels are shallow and wide, and they mostly have erosional contacts with the underlying deposits. And although the channels commonly overflowed (sand-rich sediments form poor and low-relief levees), direct contacts between the channel and thin beds are rare due to deposition, scour, and subsequent fill. The average grain size of the channel deposits is slightly larger than the levee deposits. Paleocurrents of ripples indicate a northerly transport direction within the channel while the layered levee deposits have a divergent 35° offset direction on both sides of the channels. Common sedimentary structures include parallel laminations, current ripple laminations, and climbing ripples; climbing ripples are common at this location (Figure 5).
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Atlas of Deep-Water Outcrops
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