Architecture of a Deep-water, Salt-withdrawal Minibasin, Donkey Bore Syncline, Australia
Tobias H. D. Payenberg, Carmen B. E. Krapf, Simon C. Lang, Blaise Fernandes, Mark R. W. Reilly, Nathan Ceglar, Khairul A. Mohamed Ibrahim, 2008. "Architecture of a Deep-water, Salt-withdrawal Minibasin, Donkey Bore Syncline, Australia", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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The Cambrian Donkey Bore Syncline exposes a salt-withdrawal minibasin filled with more than 500 m (1640 ft) of clastic sediments in the northern part of the Flinders Ranges, South Australia. The minibasin formed in the Early Cambrian as the Adelaide geosyncline passive margin was inverted. Analysis of salt geometries within the Flinders Ranges suggests that the Delamerian orogeny may have commenced during the latest Proterozoic (Mark G. Rowan and Bruno C. Vendeville, personal communication, 2006). If true, movement of the Willouran-aged Callanna Group salt would have been enhanced by shortening-induced folding and diapir squeezing.
The doubly folded syncline exposes shallowly dipping sediments along its three limbs across an area of approximately 21 km2 (8 mi2) next to the Wirrealpa Diapir. The minibasin was situated on the upper slope, most likely below storm wave base. It was flanked to the south by a shallow-marine clastic depositional environment during deep-water sandstone (Bunkers Sandstone) deposition. Paleocurrent data within the basin as well as the axes of slumped sandstone beds indicate sediment input from the south. The main deep-water sediments of the Bunkers Sandstone are up to 350 m (1150 ft) thick. They have an overall net-to-gross of approximately 30% and form a transgressive package with each unit becoming successively less sand-rich.
Three classes of architectural elements, ranging in thickness from 50-90 m (164-295 ft), are present in outcrop. These include 1) sandstone-rich sheets with a net-to-gross of up to 70% (Unit A), 2) sandstone-rich thin beds with net-to-gross of up to 60%
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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