Reconnaissance Geologic Map of the Dubakella Mountain 15’ Quadrangle, Trinity County, California

Synopsis

The Dubakella Mountain 15’ quadrangle is located just south of the Hayfork quadrangle and just east of the Pickett Peak quadrangle. It spans a sequence of four northwest-trending tectonostratigraphic terranes of the Klamath Mountains geologic province that includes, from east to west, the Eastern Hayfork, Western Hayfork, Rattlesnake Creek, and Western Jurassic terranes, as well as, in the southwest corner of the quadrangle, part of a fifth terrane, the Pickett Peak terrane of the Coast Ranges geologic province.

The Eastern Hayfork terrane is a broken formation and mélange of volcanic and sedimentary rocks that include blocks of limestone and chert. The limestone contains late Permian microfossils of Tethyan faunal affinity. The chert contains radiolarians of Mesozoic age, mostly Triassic, but none clearly Jurassic.

The Western Hayfork terrane is an andesitic volcanic arc that consists mainly of agglomerate, tuff, argillite, and chert, and includes the Wildwood pluton. That pluton is related to the Middle Jurassic (about 170 Ma) Ironside Mountain batholith that is widely exposed farther north beyond the Dubakella Mountain quadrangle.

The Rattlesnake Creek terrane is a highly disrupted ophiolitic mélange of probable Late Triassic or Early Jurassic age. Although mainly ophiolitic, the mélange includes blocks of plutonic rocks (about 200 Ma) of uncertain genetic relation. Some scattered areas of well-bedded mildly slaty detrital rocks of the mélange appear similar to Galice Formation (unit Jg) and may be inliers of the nearby Western Jurassic terrane.

The Western Jurassic terrane consists mainly of slaty to phyllitic argillite, graywacke, and stretched-pebble conglomerate and is correlative with the Late Jurassic Galice Formation of southwestern Oregon.

The Pickett Peak terrane, the most westerly of the succession of terranes of the Dubakella Mountain quadrangle, is mostly fine-grained schist that includes the blueschist facies mineral lawsonite and is of Early Cretaceous (about 120 Ma) metamorphic age.

Remnants of the Great Valley sequence of dominantly Cretaceous marine sedimentary strata, which once covered much of the southern fringe of the Klamath Mountains, are present at three places in the Dubakella Mountain quadrangle.

Mineral production in the quadrangle has included small amounts of gold, chromite, and manganese.

This map of the Dubakella Mountain 15’ quadrangle is a digital rendition of U.S. Geological Survey Miscellaneous Field Studies Map MF-1808, with various improvements and additions.

Also of Interest

Irwin, W.P., 2009, Geologic map of the Weaverville 15' quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3095, scale 1:50,000 [https://pubs.usgs.gov/sim/3095/].

Irwin, W.P., 2010, Reconnaissance geologic map of the Hayfork 15' quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3119, scale 1:50,000 [https://pubs.usgs.gov/sim/3119/].

Irwin, W.P., 2010, Reconnaissance geologic map of the Hyampom 15' quadrangle, Trinity County, California: U.S. Geological Survey Scientific Investigations Map 3129, scale 1:50,000 [https://pubs.usgs.gov/sim/3129/].

First posted February 23, 2011