Stratigraphic Anatomy and Depositional History of a Mass-transport Complex, Isaac Formation, Windermere Supergroup, British Columbia, Canada
Joel Laurin, Kenny Wallace, R. W. C. Arnott, Ernesto Schwarz, 2008. "Stratigraphic Anatomy and Depositional History of a Mass-transport Complex, Isaac Formation, Windermere Supergroup, British Columbia, Canada", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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Sandwiched between Isaac channels 2 and 3 is a 130-m (426-ft)-thick mass-transport complex (MTC) composed mostly of very coarse debris-flow and slump/slide deposits. The succession can be traced laterally from Castle Creek South to Castle Creek North, a distance of at least 2.2 km (1.4 mi). The anomalous abundance of debris-flow and slump/slide deposits compared to super- and subjacent strata suggests a period of slope instability that interrupted otherwise gravitationally stable slope conditions. Additionally, the abrupt increase in the size of sediment particles, composed mostly of quartz, with lesser carbonate and carbonate-cemented clasts, suggests an important change in sediment provenance.
In Castle Creek North, the MTC is a tabular unit consisting of a 55-m (180-ft)-thick slide/slump overlain by a 16-m (53-ft)-thick, carbonate-clast-rich, debris-flow deposit. In the slide/slump unit, ductile and brittle deformation structures are common, and clasts consist of a diverse assemblage of low-total-organic-content mudstone and arkosic-sandstone blocks, some ranging up to a few tens of meters (>100 ft) long and several meters (few tens of ft) thick. The debris-flow deposit consists of dispersed quartz pebbles, carbonate-cemented mudstone and common shallow-water stromatolite and oolite fragments. In Castle Creek South, the MTC is a significantly more complicated melange comprising a number of erosively based units. Near the glacier in Castle Creek South, the succession is about 60 m (200 ft) thick and comprises a basal, coarse quartz-pebble-conglomerate that is overlain by a 20-m- (65-ft)-thick slide deposit. The slide deposit is capped by a 30-m (100-ft)-thick mudstone-rich, debris-flow deposit, commonly with dispersed,
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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