- Usage in publication:
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- Walcott Member
- Modifications:
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- First used
- AAPG geologic province:
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- Plateau sedimentary province
Summary:
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).
- Usage in publication:
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- Walcott Member
- Modifications:
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- Named
- Dominant lithology:
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- Limestone
- Dolomite
- AAPG geologic province:
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- Southern Rocky Mountain region
Summary:
Named as the upper member of Kwagunt Formation (new) of Chuar Group for Walcott Glen, west of Colorado River, Coconino Co, AZ in the Southern Rocky Mountain region. Type section is at head of the glen and in upper part of Nankoweap Butte. Is also exposed in Awatubi and Sixty Mile Canyons. Overlies Awatubi Member (new) of Kwagunt. Basal contact placed at base of flaky dolomite, a buff-weathering dolomite 8 ft thick with some oolite lenses which has relics of algal lamination in form of silicified flakes 1+ inch in length and 1/4 inch thick. Aspect of this unit is of disrupted laminar stromatolitic limestone which has been dolomitized and subsequently silicified. Disruption caused by contemporary sea-floor slumping. Blue-gray shale about 66 ft thick with scattered CHURIA overlies the dolomite bed followed by silicified oolite, pisolitic chert, blue-black shale, cherty oolite, and dolomitic limestone in two beds 25 and 40 ft thick that form the top of the member. Is overlain unconformably by Sixty Mile Formation (new) of Chuar. Is 838 ft thick on east face Nankoweap Butte. Corresponds to Division 2 and 9 of Walcott (1899) and Division 7 of Hinds (1935). Of late Precambrian age. Geologic map.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
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- Walcott Member*
- Modifications:
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- Adopted
- AAPG geologic province:
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- Plateau sedimentary province
Summary:
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).
- Usage in publication:
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- Walcott Member*
- Modifications:
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- Age modified
- AAPG geologic province:
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- Plateau sedimentary province
Summary:
Age of the Walcott Member of the Kwagunt Formation is modified from Precambrian to: Proterozoic Y.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Walcott Member*
- Modifications:
-
- Age modified
- AAPG geologic province:
-
- Southern Rocky Mountain region
Summary:
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).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).