The Effect of Slumping on Sandstone Distribution in the Arro Turbidites, Los Molinos Road, Spain
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Pau Arbués, Donatella Mellere, Marta Puig, Mariano Marzo, 2008. "The Effect of Slumping on Sandstone Distribution in the Arro Turbidites, Los Molinos Road, Spain", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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Abstract
The Arro turbidites (Eocene San Vicente Formation) were deposited as part of the infill of the Ainsa basin during the foredeep stage of basin development. Their maximum thickness is 180 m (590 ft) with a preserved length of 16 km (10 mi) and width of 4 km (2.5 mi). Net-to-gross is approximately 40%. The Arro turbidites have been interpreted as a canyon-mouth sheet system that was deposited in a base-of-slope setting. The system is elongate with deposition occurring in the axis of the foredeep basin. Flanking the deposits was an active margin slope. The Arro turbidites have been correlated updip to a canyon fill that is incised in shelf deposits. The Los Molinos road outcrop is a partial section of the Arro turbidites. This section is 180 m (590 ft) long, transverse to the northwest-directed paleoflow. It is located approximately 4.2 km (2.6 mi) from the canyon-fill locality. Here, the Arro turbidites rest on top of a mudstone succession and reach their maximum thickness (180 m [590 ft]). Four classes of architectural elements, ranging in thickness from 1–20 m (3–66 ft), are present in the outcrop. These include 1) mudstone-rich, thin-bed elements (TM) with net-to-gross up to 30%, 2) sandstone-rich, thin-bed elements (TS), with variable net- to-gross (30–70%) and common erosive bedding, 3) thick-bed elements (C), mostly channel forms, with net-to-gross up to 90%, and 4) slump-deformed, mudstone-dominated units (SM). The lower interval of the studied succession (lower two-thirds of exposure) contains abundant slumps and thin beds. channel forms are rare, and where present,
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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