First use of the Walcott Member of the Kwagunt Formation of the Chuar Group. Age is Precambrian.

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

Pg. 1244 (table 1), 1252, 1253 (fig. 10), geol. map (fig. 1), columnar section (fig. 2). Walcott Member of Kwagunt Formation of Chuar Group. Consists of (ascending): (1) buff-weathering flaky dolomite, about 8 feet thick, at base; (2) blue-gray shale with scattered CHUARIA, about 66 feet thick; (3) pisolitic chert bed (also called cherty pisolite), about 2 feet thick, forms prominent ledge; (4) blue-black shale [about 420 feet thick], includes thin limestone beds in upper part; (5) "top dolomite", = two layers of dolomitic limestone, about 25 and 40 feet thick, separated by about 40 feet of shale; and (6) blue-gray shale, about 228 feet thick, at top. Total thickness measured at type section on east face of Nankoweap Butte about 838 feet (255 m). Is top member of Kwagunt Formation (new). Overlies Awatubi Member (new) of Kwagunt. Unconformably underlies chert and breccia of Sixty Mile [Sixtymile] Formation (new), top formation of Chuar Group [chart accompanying geol. map (fig. 1) incorrectly shows the Sixtymile excluded from Chuar Group]. Appears = Walcott's [upper] divisions 2 through 9 of Chuar terrane [USGS Ann. Rpt. 14, p. 508-509, 1894], and upper part of Hinds' division 7 of Chuar Group [Carnegie Inst. Washington Pub. 463, p. 105-106, 1936]. Fossils. [See also T.D. Ford and W.J. Breed, 1973, The problematical Precambrian fossil CHUARIA: Palaeontology, v. 16, pt. 3, p. 535-550.] Age is late Precambrian.
Type section: Walcott Glen section G, [extends from head of Walcott Glen (not an official name of U.S. Board on Geographic Names), approx. Lat. 36 deg. 15 min. 40 sec. N., Long. 111 deg. 52 min. 34 sec. W. upslope to near top of Nankoweap Butte, approx. Lat. 36 deg. 15 min. 55 sec. N., Long. 111 deg. 52 min. 55 sec. W., southeastern corner Point Imperial 7.5-min quadrangle], eastern Grand Canyon, Grand Canyon National Park, Coconino Co., northern AZ.
Named from Walcott Glen [unofficially named by authors; see their figs. 1, 10], which branches northwest from the lower parts of Kwagunt Canyon to head on the southeastern slopes of Nankoweap Butte, [Nankoweap Mesa and Point Imperial 7.5-min quadrangles], 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.]

Source: Publication; supplemental information from US geologic names lexicon (USGS Bull. 1520, p. 326).

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

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

Age of the Walcott Member of the Kwagunt Formation is modified from Precambrian to: Proterozoic Y.

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

Is the upper member of Kwagunt Formation of Chuar Group of Grand Canyon Supergroup. Unconformably underlies Sixtymile Formation. Contains the greatest abundance and diversity of microfossils and stromatolites of any unit in the Chuar. Is 281 m thick. Age designation of Proterozoic Y changed to Late Proterozoic, the term applied to rocks younger than 900 Ma and older than 570 Ma. Change in age designation made to Kwagunt and its Carbon Butte, Awatubi, and Walcott Members in the Southern Rocky Mountain region of northern AZ.

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