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- Usage in publication:
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- Bass Lake Tonalite*
- Modifications:
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- Named
- Geochronologic dating
- Dominant lithology:
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- Tonalite
- AAPG geologic province:
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- Sierra Nevada province
Summary:
Named for exposures along shores of Bass Lake. Type locality is Bass Lake [37 deg 19' 12"N, 119 deg 33' 24"W, Madera Co, CA]. Is oldest formally named unit of Fine Gold Intrusive Suite (new). Formerly rocks at entrance to Yosemite called The Gateway by Calkins (1930) and Gateway Granodiorite by Evernden and others (1957); extensive area in southwest part mapped area called tonalite of Blue Canyon (preempted name). Mostly forms single large pluton with several smaller plutons assigned to unit; fig. map shows Poopenaut Valley, Hazel Green and Indian Flat plutons. Typical rock is medium-gray, medium-grained equigranular tonalite with conspicuous foliation. Intrudes and is intruded by metamorphic rocks. U-Pb ages range from 124 to 105 Ma, although optimum age considered to be 117 to 111 Ma with average of 114 Ma, thus Early Cretaceous.
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 ([ ]).