- Usage in publication:
-
- Jackhammer Formation*
- Modifications:
-
- Named
- Dominant lithology:
-
- Sandstone
- Siltstone
- Tuff
- Limestone
- AAPG geologic province:
-
- Mojave basin
Summary:
Named by McCulloh (1952, unpublished thesis) and here adopted. Is discontinuous thin basal sedimentary and volcanic formation exposed only in Mud Hills; best exposed in Owl Canyon; 150 ft maximum thickness. Lower 30-100 ft arkosic sandstone and siltstone; upper part 5-20 ft bedded white tuff overlain by 5-30 ft vesicular basalt. Half mile east of Owl Canyon, formation composed of lenses up to 50 ft thick of gray limestone; further east composed of granitic boulder conglomerate. Unconformable on quartz monzonite. Overlain by Pickhandle Formation. Age presumably Oligocene or early Miocene.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Jackhammer Formation*
- Modifications:
-
- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- Mojave basin
Summary:
Age of Jackhammer Formation is revised from Oligocene or early Miocene to early Miocene based on stratigraphic position between radiometrically-dated volcanic units (18.9 +-1.3 Ma date on overlying Opal Mountain Volcanic Member of Pickhandle Formation and 23.1+-0.2 Ma for underlying Lane Mountain Quartz Latite).
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 ([ ]).