WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES OPEN FILE REPORT 2003-6
Division of Geology and Earth Resources Ron Teissere - State Geologist R. 3 W. Qgd Qgd Qgd Qgd Qgt Qgdm es Qf KJmm c Qgt T. 35 N.
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Tertiary Sedimentary and Volcanic Rocks ROCKS OF THE CRESCENT TERRANE OF BABCOCK AND OTHERS (1994) Twin River Group—Divided into:
Pre-Tertiary Marine Metasedimentary Rocks
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Geologic Map of the Washington Portion of the Port Angeles 1:100,000 Quadrangle
by Henry W. Schasse 2003
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T. 34 N.
Pysht Formation (Miocene–Oligocene)—Massive, poorly indurated marine mudstone, claystone, and sandy siltstone; also contains beds of very thick calcareous sandstone (1–20 ft thick). Unweathered mudstone, claystone, and siltstone are medium gray to dark greenish gray, pale yellowish brown where weathered. Mudstone locally contains thin beds of calcareous claystone; argillaceous rocks commonly contain sparsely disseminated calcareous concretions that are spherical, cylindrical, or irregular in shape. Mollusk shell fragments, foraminifera, and carbonized plant material are common in mudstone. Gradational with the underlying Makah Formation (unit …Emm)(Snavely and others, 1978). Contains Saucesian and upper Zemorrian foraminifera (Rau, 1964, 1981, 2000, 2002); mollusks are indicative of the Juanian Stage (Addicott, 1976, 1981). (Description compiled from Brown and others, 1960; Schasse and Wegmann, 2000.) Makah Formation (Oligocene–Eocene)—Massive to locally thinand rhythmically bedded siltstone and mudstone and minor thin-bedded sandstone; generally greenish gray to olive-brown, weathers to grayish orange and yellowish brown; locally dark gray to black where carbonaceous; spherical calcareous concretions (often containing fossil shells and plants) and nodules occur throughout. Sandstone is very fine to medium grained, subquartzose, and feldspatholithic, and is most common in the eastern part of the map area. Gradational with the underlying Hoko River Formation (unit Em2h)(Snavely and others, 1978). Contains upper Narizian and Refugian foraminifera (Rau, 1964, 2000, 2002). (Description compiled from Brown and others, 1960; Schasse and Logan, 1998.) Locally divided into: Conglomerate and granule sandstone—Massive pebble– cobble conglomerate and granule sandstone cropping out at the base of unit …Emm 2 mi west of the Elwha River. Conglomerate is composed of pebbles and cobbles of varied lithology (similar to the Lyre Formation, unit Em2lc) in a matrix of coarse-grained to granule sandstone. A sedimentary breccia composed almost entirely of angular volcanic debris is sporadically exposed at the base of the conglomerate (Brown and others, 1960). Subquartzose, feldspatholithic, medium- to thick-bedded, mediumgrained to granule sandstone that grades to small-pebble conglomerate crops out at the base of unit …Emm on Bell Hill south of Sequim; rounded pebble clasts consist of basaltic material eroded from the Crescent Formation (unit Evcf). Contains marine pelecypod and brachiopod macrofossils and oyster shell fragments (Schasse and Logan, 1998); also contains Refugian foraminifera (Rau, 1998).

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