- Usage in publication:
-
- Blackjack formation
- Modifications:
-
- Named
- Dominant lithology:
-
- Quartzite
- AAPG geologic province:
-
- Basin-and-Range province
Summary:
Sequence of older Precambrian volcanic and sedimentary rocks more than 15,000 ft thick occurs in Blackjack Mountains and White Ledges, 20 mi north of Globe, AZ. This sequence consists of (older to younger); Redmond formation (acidic volcanic rocks) and Hess Canyon group (clastic sedimentary rocks. Hess Canyon is subdivided into: White Ledges formation, Yankee Joe formation, and Blackjack formation. Blackjack formation consists of argillaceous quartzite. Is intruded by Ruin Granite and diabase. Unconformably underlies younger Precambrian Apache Group.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Blackjack Formation
- Modifications:
-
- Age modified
- AAPG geologic province:
-
- Basin-and-Range province
Summary:
Shown in geologic column of Salt River Canyon as Middle Proterozoic age and from 1000 to 7700 feet thick although "not seen in canyon". Shown on geologic cross-section of Corral Canyon area where unit unconformably underlies "Whitetail Conglomerate" of Eocene to Oligocene age (Moore, 1968, p.60).
Source: GNU records (USGS DDS-6; Menlo 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 ([ ]).