Stratigraphic Architecture of a Channel Complex in the Canyon-mouth Setting of the Lower Pab Basin-floor Fan, Drabber Dhora, Pakistan
E Albouy, R Deschamps, T Euzen, R Eschard, 2008. "Stratigraphic Architecture of a Channel Complex in the Canyon-mouth Setting of the Lower Pab Basin-floor Fan, Drabber Dhora, Pakistan", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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The outcrops are located in southern Pakistan in the southern part of the Pab mountain range, in a north-south-trending monocline more than 200 km (125 mi) long. In this area, the late Maastrichtian Pab Formation consists of turbidite and gravity-flow deposits in a lower slope to basin setting. The Pab mountain belt is incised by dry river gullies, which provide excellent, large-scale 3-D exposures of the architecture of the Pab Formation. At the base of the Pab Formation outcrop belt, a sand-rich turbidite system is preserved from the canyon setting to the lobes of the basin floor fan. This lower Pab Formation turbidite system consists of three vertically stacked channel complexes organized in a backstepping succession onlapping the paleomargin, each one more than 100 m (330 ft) at its thickest point. The following pages describe the three stacked channel complexes in the Drabber Dhora outcrop, which is interpreted as being located at the canyon mouth of the lower Pab Formation turbiditic system. These channel complexes consist of several multistory, individual channels that are stacked vertically because of the confinement of the system. The vertical organization of the complex is overall backstepping. At the base of the complex, bypass facies dominate, whereas fill and then spill deposits become dominant towards the top. During the erosional stage of individual channels, bypass facies were deposited (mud-clast lags, tractive megadunes, gravel lags, and monogenic debris flows), while overflow deposits (levees) were deposited laterally to the channel axis. Overflow deposits are poorly developed in the canyon-mouth setting because of the confinement of the system.
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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