Stratigraphic Architecture and Depositional Evolution of a Levee te Proximal Crevasse-splay to Channel-fill Succession: Units 13 and 14, Castle Creek North, Isaac Formation, Windermere Supergroup, British Columbia, Canada
R. W. C. Arnott, 2008. "Stratigraphic Architecture and Depositional Evolution of a Levee te Proximal Crevasse-splay to Channel-fill Succession: Units 13 and 14, Castle Creek North, 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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High-resolution seismic surveys of many modern deep-water channel systems suggest that channels commonly overlie a genetically related, sheetlike, sand-rich unit termed a high amplitude reflection package (HARP), which is interpreted to be the result of channel avulsion and flow diversion (Hiscott et al., 1997). Because of their sand-prone composition, and sometimes poor conventional core recovery, knowledge of their stratigraphic and lithological attributes is limited (Hiscott et al., 1997). However, at Castle Creek North, a deep-marine channel-fill complex and genetically related subjacent strata are well exposed in rocks of the Windermere Supergroup. At the base of Unit 13, thin-bedded, upper-division turbidites (Tc-e) are interstratified with thicker, coarser grained, more complete turbidites. Respectively, these strata are interpreted to be fine-grained levee and overbank-splay deposits related to an active but not exposed channel. These strata are then overlain abruptly by a 23-m (75-ft)-thick succession consisting of thin-bedded, fine- to medium-grained sandstone Ted turbidites intercalated with medium-bedded, graded (coarse-tailed), structureless, medium-grained sandstone.
This succession is interpreted to be a proximal crevasse splay or HARP deposit related to the avulsion of an adjacent, previously active channel. High-energy turbulent suspensions, now diverted through the levee breach and into the interchannel area, expanded rapidly, lost transport capacity, and incrementally constructed the crevasse splay. Depending on the rate of turbulent suspension collapse, one of two lithofacies were deposited: Ted turbidites were deposited from low-concentration dispersions, whereas structureless sandstone accumulated rapidly from high-concentration suspensions formed in submerged hydraulic jumps (turbidites were deposited from reconstituted dispersions
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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