First use of the Galeros Formation of the Chuar Group. Consists of the (ascending) Tanner, Jupiter, Carbon Canyon, and Duppa Members. Age is late Precambrian.

Source: GNU records (USGS DDS-6; Menlo GNULEX).

Pg. 1244 (table 1), 1245+, geol. map (fig. 1), columnar section (fig. 2). Galeros Formation of Chuar Group. Mostly shale with lesser limestone, dolomite, siltstone, and sandstone. Subdivided into newly named members (descending): Duppa, about 570 feet; Carbon Canyon, about 1,546 feet; Jupiter, about 1,516 feet; and Tanner, about 640 feet [see entries under individual members]. Total thickness about 4,272 feet. Underlies Kwagunt Formation (new) of Chuar Group. Unconformably(?) overlies sandstones of Nankoweap Group; contact is not easily accessible. Fossils. Age is late Precambrian.
[Type locality not stated. Formation exposed south of Galeros promontory (not an official name of U.S. Board on Geographic Names), in areas around Carbon Butte and Chuar Canyon [Chuar Valley], Cape Solitude 7.5-min quadrangle, eastern Grand Canyon, Grand Canyon National Park, Coconino Co., northern AZ.]
Named from Galeros promontory. [Unofficially named by authors; see their geol. map (fig. 1). Located south of Sixty Mile Canyon [Sixtymile Canyon], between Galeros and Chuar Buttes, Cape Solitude 7.5-min quadrangle, eastern Grand Canyon, Grand Canyon National Park, Coconino Co., northern AZ.]
[Additional locality information from USGS historical topographic map collection TopoView, accessed on October 1, 2024.]
[Typographical error (US geologic names lexicon, USGS Bull. 1520, p. 110): type section stated to be in Galeros promontory (labeled on geol. map, fig. 1). Cambrian Tapeats Sandstone mapped in Galeros promontory. Galeros Formation exposed in areas to south.]

Source: Publication; supplemental information from US geologic names lexicon (USGS Bull. 1520, p. 110).

Galeros Formation of the Chuar Group of Ford and Breed (1973) is adopted as the Galeros Formation of the Chuar Group of the Grand Canyon Supergroup. Age is late Precambrian.

Source: GNU records (USGS DDS-6; Menlo GNULEX).

Age of the Galeros Formation is modified from late Precambrian to: Proterozoic Y.

Source: GNU records (USGS DDS-6; Menlo GNULEX).

Is the basal formation of the Chuar Group of the Grand Canyon Supergroup. Unconformably overlies Nankoweap Formation. Underlies Kwagunt Formation of Chuar. Is 1,010 m thick. Age designation of Proterozoic Y changed to Late Proterozoic, the age term applied to rocks younger than 900 Ma and older than 570 Ma. Change in designation made to Galeros and its Tanner (base), Jupiter, Carbon Canyon, and Duppa Members in the Southern Rocky Mountain region of northern AZ. Span of Galeros shown as extending from 900 Ma (est) to 850 Ma (est). Columnar section.

Source: GNU records (USGS DDS-6; Denver GNULEX).