Provenance of conglomerate clasts from Upper Cretaceous Kuskokwim group, southwest Alaska
The predominantly Upper Cretaceous (Albian to Coniacian) Kuskokwim Group consists of marine turbidites and subordinate fluvial and shallow marine strata, deposited in an elongate southwest-trending basin covering over 70,000 km/sup 2/ in southwestern Alaska. In the Sparrevohn and Cairn Mountain areas of the Lime Hills A-7 and A-8 quadrangles, fluvial, inner fan, middle fan, and outer fan facies are stacked with distal facies over proximal facies by northwest vergent thrust faults. Inner fan pebble-to-cobble conglomerate and pebbly sandstone were deposited as submarine grain flows up to 10 m thick containing reversely graded bases and normally graded tops. Clasts from these conglomeratic deposits are predominantly sedimentary rock fragments - particularly sandstone, siltstone, and argillite - originally through to have been derived from the nearby Jurassic and Lower Cretaceous flysch (Kihiltna terrane). Detailed examination of these clasts, however, indicate that they contain as minor constituents Paleozoic coral, oolitic limestone, algal boundstone, radioarian chert, and mafic, intermediate, and felsic volcanic rocks, most likely derived from the adjacent Nixon Fork, Killinger, and Mystic terranes. Sandstone clasts are arkosic (Q25-F37-L38, n = 7) and contain subequal amounts of K-feldspar and plagioclase. Sand grains within these clasts are moderately sorted, subrounded, and have presolved contacts. Similar arkosic rocks have been described from the Killinger terrane of the McGrath quadrangle and are the most likely source for the pebbles and cobbles within the Kuskokwim Group.
- OSTI ID:
- 6455669
- Report Number(s):
- CONF-8505215-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 69:4; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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