1997
DOI: 10.3133/ofr97475
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Geologic map of the Nabesna A-6 quadrangle, Alaska

Abstract: Qal Alluvium along streams (Holocene)-Mainly in active flood plains of major and some minor streams. Locally, includes outwash related to older phases of the Alaska glaciations. Chiefly stratified boulders, cobbles, gravel, and sand; silt locally common. Qaf Alluvium in fans (Holocene)-Mainly large active fans and cones on steep to gentle slopes adjacent to the broad glaciated valley of the Copper River. Chiefly poorly stratified boulders, cobbles, gravel, and sand. COLLUVIAL DEPOSITS Qc Colluvium, undifferent… Show more

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Cited by 8 publications
(19 citation statements)
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“…These porphyritic to equigranular gabbro sills contain 40-60 percent primary pigeonite, clinopyroxene, and orthopyroxene, which are often overgrown by hornblende and chlorite; also present are about 40 percent twinned plagioclase, which is often completely replaced by white mica or chlorite, and up to 10 percent titanite. Unit correlates with gabbroic intrusions (unit ^gb) of Dashevsky and others (2003), which were assigned a Middle Triassic age in the Delta mineral belt, and greenstone (unit Dg) of Richter (1976). Magnetic susceptibility is moderate, but can be much higher locally (0.01-70, averaging 0.9 x 10 -³ SI).…”
Section: Metasedimentary and Metaigneous Rocksmentioning
confidence: 99%
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“…These porphyritic to equigranular gabbro sills contain 40-60 percent primary pigeonite, clinopyroxene, and orthopyroxene, which are often overgrown by hornblende and chlorite; also present are about 40 percent twinned plagioclase, which is often completely replaced by white mica or chlorite, and up to 10 percent titanite. Unit correlates with gabbroic intrusions (unit ^gb) of Dashevsky and others (2003), which were assigned a Middle Triassic age in the Delta mineral belt, and greenstone (unit Dg) of Richter (1976). Magnetic susceptibility is moderate, but can be much higher locally (0.01-70, averaging 0.9 x 10 -³ SI).…”
Section: Metasedimentary and Metaigneous Rocksmentioning
confidence: 99%
“…No fossils have been found in the map area; Devonian age designation is based on the presence of Middle Devonian corals in similar metamorphic rocks in the adjacent Nabesna quadrangle (Richter, 1976 to lateral variation during protolith deposition. Dashevsky and others (2003) describe the Drum Unit as "a relatively thin, felsic unit composed of white to pale gray-green, rusty weathering, fine-grained quartzeye-bearing quartz-sericite ±chlorite ±pyrite schist with minor gray to black carbonaceous phyllite and rare chloritic phyllite interbeds.…”
Section: Mdgs Graphite-bearing Quartz Schist With Lesser Metavolcanicmentioning
confidence: 99%
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“…The metamorphic protolith of the Maclaren terrane is interpreted to be flysch similar to rocks that make up the Kahiltna terrane (Richter, 1976;Smith, 1981;Stout, 1976). This terrane includes extensively exposed Upper Jurassic and Lower Cretaceous flysch that is interpreted to be a remnant of a Jurassic and Cretaceous basin that originally extended for several thousand kilometers along the margin of the North American Cordillera.…”
Section: Terranes South Of the Denali Faultmentioning
confidence: 99%
“…12). Cross-cutting relationships of dikes and plutons constrain the age of the Lost Creek detachment to be Cretaceous (Richter et al, 1977;Richter, 1976;and Richter and Schmoll, 1973) during which regional compressional deformation events were recorded throughout Wrangellia and the western margin of North America (Refs).…”
Section: Large Kink Folds In the Mccarthy Formation Eastern Alaska Rmentioning
confidence: 99%