Lithofacies and Depositional Architecture of an Upper Fan Channel Complex, Punta Naranjo, Nicaragua
I. Struss, C. Brandes, C. Vandré, J. Winsemann, 2008. "Lithofacies and Depositional Architecture of an Upper Fan Channel Complex, Punta Naranjo, Nicaragua", Atlas of Deep-Water Outcrops, Tor H. Nilsen, Roger D. Shew, Gary S. Steffens, Joseph R. J. Studlick
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Deep-water channel-levee complexes of the middle to upper Eocene Brito Formation are extensively exposed along the Pacific coast of southwestern Nicaragua across a distance of more than 70 km (43 mi) and have a total thickness of approximately 2500 m (8200 ft). The Brito Formation forms part of an up to 13 km (8 mi) thick sedimentary infill of the Sandino forearc basin consisting of Late Cretaceous to Holocene deep- to shallow-marine and continental pyroclastic deposits. Coastal outcrops parallel and perpendicular to bed trends allow the reconstruction of laterally and vertically stacked channel-levee complexes. Each channel-levee complex consists of several (one to seven), probably shingled, channel-levee systems with a feeder or distributary channel near the center. Individual channel-levee complexes are 80 to 120 m (262 to 393 ft) thick and 5 to 11 km (3 to 7 mi) wide. Levee deposits are mainly tabular and have been interpreted on the basis of bed thickness, grain size, occurrence of climbing ripples, convolute lamination, and rip up clasts (CCC elements; Walker, 1984), lateral facies changes, variations in the local paleoslope, and locally intercalated crevasse deposits. A channel complex and its associated levees at Punta Naranjo are described and analyzed in detail. This complex consists of two offset-stacked channel fills with low aspect ratios. The u-shaped channels are filled with high net-to-gross, matrix-supported conglomerates and pebbly sandstones. The most complete channel fill of this section is characterized by a coarse-grained axial fill above a lower erosive surface and finer grained, thinner bedded, channel-margin deposits within its lower part.
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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