- Usage in publication:
-
- Roblar leucogranite*
- Modifications:
-
- Named
- Dominant lithology:
-
- Granite
- AAPG geologic province:
-
- Peninsular Ranges province
Summary:
Named for its occurrence in Roblar Canyon, northern part of San Luis Rey 30' quad, San Diego Co, CA. Extends some distance to north and east, underlying area of about 15 sq mi. Leucogranite is uniform in character, flesh-colored and aplitic in appearance. In uplands forms small hills; in canyons shows angular, blocky or sheeted outcrops nearly white in color. Chemical analysis included. Is younger than granodiorite of Santa Margarita Mountain and Woodson Mountain granodiorite (new). Map legend gives age as Cretaceous
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Roblar Leucogranite*
- Modifications:
-
- Geochronologic dating
- AAPG geologic province:
-
- Peninsular Ranges province
Summary:
Pg. 10, geologic time scale (inside front cover). Roblar Leucogranite. Sample from DeLuz, Lat. 33 deg. 23 min. 00 sec. N., Long. 117 deg. 19 min. 00 sec. W., Fallbrook quadrangle, San Diego County, California, yielded a Pb-alpha age of 100 +/-20 Ma (zircon) [Cretaceous]; reconnaissance age, probable time of emplacement. Age calculated using decay constants of Steiger and Jager, 1977 (Earth Planet. Sci. Letters, v. 36, p. 359-362).
Source: Publication
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 ([ ]).