- Usage in publication:
-
- Chiltepines Member*
- Modifications:
-
- Named
- Dominant lithology:
-
- Shale
- Arkose
- Quartzite
- Conglomerate
- AAPG geologic province:
-
- Basin-and-Range province
Summary:
Named as top member of Pitoikam Formation. Type locality is on tributary of Fresnal Wash west slope of Baboquivari Mountains, Pima Co, AZ about 6 mi east of the village of Pitoikam in the Basin-and-Range province. Composed mostly of maroon and green shale containing thin beds of arkose and quartzite. There is conglomerate at the base and andesite breccia flows at the top. Weathers easily. Forms narrow valley between ridges. Conglomerate near base composed mostly of quartz latite porphyry fragments. Higher in the section, the conglomerates contain fragments of dacite and andesite. The green arkosic beds are mostly fragments of dacite. Lateral lithologic beds are abrupt. No single bed can be traced more than a few hundred ft. Geologic map; mapped in eastern parts of Ts18 and 19S, R9E. Overlies Contreras Conglomerate Member (new) of Pitoikam. Overlain by Mulberry Wash Volcanic Formation (new). Is of Mesozoic? age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Chiltepines Member*
- Modifications:
-
- Age modified
- AAPG geologic province:
-
- Basin-and-Range province
Summary:
Age refined from Mesozoic? to Early Jurassic.
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 ([ ]).