Distal-basin-floor-fan Deposits of the Middle Eocene Tyee Formation, Oregon,USA
M. L Sweet, R. T Beaubouef, John Beuhler, Matt Grove, Margie Kloska, Steve Mitchell, 2008. "Distal-basin-floor-fan Deposits of the Middle Eocene Tyee Formation, Oregon,USA", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
Download citation file:
The middle Eocene Tyee Formation was deposited in the Oregon Coast Range fore-arc basin (Figure 1). Heller and Ryberg (1983) and Ryu and Niem (1999) describe the Tyee Formation as part of a 6-km (3.7-mi)-thick package of sedimentary rocks that rests unconformably on the Paleocene Siletz River Volcanics (Figure 2). The Umpqua Arch (Figure 1) appears to have influenced deposition of the Tyee and divided the basin into two sub basins. Field mapping by chan and Dott (1983) and Heller and Dickinson (1985) suggests that the Tyee depositonal system includes fluvial and deltaic deposits to the south and that this system prograded to the north through time.
Outcrops of the middle Eocene Tyee Formation along Highway 20, west of Corvallis, Oregon, display facies that are characteristic of the distal end of a sand-rich basin-floor fan. This area is more than 100 km (60 mi) basinward of slope and deltaic deposits of the Tyee Formation (Figures 1 and 3). A series of road cuts along Highway 20 exposes up to 460 m (1500 ft) of strike section that shows no evidence of channelization (Figure 4). The primary sedimentary facies here are relatively thick (1-3 m [3-10 ft]) beds of massive sandstones (Ta). These beds are, in many cases, capped by thin (0.2-0.6-m [0.7-2.0-ft]-thick) beds of organic-rich, muddy, fine-grained sandstones that contain rip-up clasts (Figures 5-7). We interpreted these muddy beds as slurry deposits (sensu Lowe and Guy, 2000), that is, deposits that record a flow transitional between turbidity currents and debris flows.
Figures & Tables
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