- Usage in publication:
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- Gleeson quartz monzonite*
- Modifications:
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- Named
- Dominant lithology:
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- Quartz monzonite
- AAPG geologic province:
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- Pedregosa basin
Summary:
Pg. 8, 55-59, pl. 5. Gleeson quartz monzonite. Consists of three principal facies. The first two facies, collectively called main facies, differ chiefly in the obvious alteration that has affected one and not the other and are mapped together. Main facies is coarse-grained, light-gray rock that ranges to greenish-gray where highly chloritized and to pink where it contains sufficient pink microcline; weathered surfaces commonly rusty brown. Practically all stages of alteration of main facies of the quartz monzonite recognized, from nearly unaltered normal igneous rocks to recrystallized gneissic rocks, though most of the formation is crystalloblastic-cataclastic in texture and some parts practically entirely cataclastic and grade into true mylonites. Third facies, alaskite facies, differs from other two in being practically devoid of dark minerals. Rock ranges from practically white through pale to pinkish-gray. Rock ranges from fine aplitic-appearing material to fairly coarse in texture. Nearly all contacts of Gleeson quartz monzonite are with alluvium or are faults; overlapped by some of the Tertiary S O volcanics (new) locally; cuts Precambrian Pinal schist near South Pass. Age is Triassic or Jurassic. Report includes geologic map.
Crops out over an area of nearly 30 sq mi, in T. 18 and 20 S., R. 24 and 25 E., in southern part of Dragoon Mountains, and in pediment to south and east of it, central Cochise Co., southeastern AZ. Town of Gleeson is at eastern side of the mass, and the Gleeson-Tombstone Road crosses it near its center.
Source: US geologic names lexicon (USGS Bull. 1200, p. 1517-1518).
- Usage in publication:
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- Gleeson Quartz Monzonite*
- Modifications:
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- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- Pedregosa basin
Summary:
Dated by K-Ar method as 178 Ma (S. C. Creasey, oral communication, 1968). Is in the Pedregosa basin. Is of Early Jurassic age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Gleeson Quartz Monzonite*
- Modifications:
-
- Age modified
- Geochronologic dating
Summary:
Dated as 181 +/-5.4 m.y. K-Ar on biotite (R. F. Marvin, oral communication, 1975) taken from sample of main body of Gleeson, which supports a Jurassic age assignment rather than Triassic or Jurassic, the age applied in earlier reports. Is in the Pedregosa basin.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Gleeson Quartz Monzonite*
- Modifications:
-
- Age modified
- Geochronologic dating
- AAPG geologic province:
-
- Pedregosa basin
Summary:
Samples collected from Gleeson Quartz Monzonite in the Dragoon Mountains area, Cochise Co., AZ. Recalculated K-Ar ages are 185 +/-4 Ma and 183 +/-5 Ma.
Source: Modified from 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 ([ ]).