Architecture of Proximal Midfan Levee Deposits, Punta Farallónes La Flor, Nicaragua
C. Brandes, I. Struss, C. Vandré, J. Winsemann, 2008. "Architecture of Proximal Midfan Levee Deposits, Punta Farallónes La Flor, Nicaragua", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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Excellent exposures along the coast of southwestern Nicaragua allow description and interpretation of middle to upper Eocene, coarse-grained channel-levee complexes of the Brito Formation, which form part of a 10–13-km (6.2–8-mi)-thick fill of the Sandino forearc basin. The up to 2500-m (8200-ft)-thick deep-water rocks consist of seven, vertically stacked, channel-levee complexes. Coastal exposures perpendicular and parallel to the depositional trend allow an analysis of variations in architecture and lithofacies of the channel-levee complexes. Each complex consists of several (one to seven) laterally stacked, probably shingled, channel-levee systems with a feeder or distributary channel near the center. Associated sheetlike deposits are interpreted as levees, based on bed thickness, grain size, occurrence of climbing ripples, convolute laminations, and rip-up clasts (CCC elements; Walker, 1984), lateral facies evolutions, variations in the local paleoslope, and intercalated crevasse deposits. The channel-levee complexes are 80–120 m (262–393 ft) thick and can be laterally traced for about 5–11 km (3–7 mi). The following pages show a longitudinal section through a channel-levee system, which outcrops in the area of Punta Farallónes La Flor. The channel fill has a lens-shaped geometry in cross section and is filled with thick- to very thick-bedded, amalgamated sandstones and thick- to very thick-bedded pebbly sandstones. Deposits formed from cohesive debris flows, sandy debris flows, and high-density turbidity currents (HDTs). The beds are massive or planar-parallel stratified. The channel axis trends north-northwest to south-southeast. Paleoflow direction was towards the north-northwest. A few beds of the channel fill are rich in large (up to 32 cm [12.6 in.]) siltstone rip-up clasts.
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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