Geologic history of the southern Baboquivari Mountains, south-central Arizona
South-central Arizona is generally believed to have been cratonic throughout Paleozoic time and part of a continental magmatic arc during the Mesozoic Era, yet the compositions of, and relict sedimentary structures in, some of the metamorphic rocks of the southern Baboquivari Mountains suggest that a marine environment existed for at least part of the Early Jurassic period. Metamorphosed from Early Jurassic protoliths, these rocks include abundant quartzo-feldspathic schists, calc-silicate schists, and metarhyolite, common finely cross-bedded quartzite interlayered with marble, subordinate metaconglomerate and metabasite, minor piemontite and spessartine bearing schists and granofels, and minor stratiform tourmalinite which may exhibit detrital sedimentary features. Marble, Mn- bearing rocks, and tourmalinite have not been noted by other workers in rocks of similar age in the northern Baboquivaris, which have been interpreted as part of a continental magmatic arc. Five generations of structures have been identified in the field: 1) Rootless fold hings of varying orientation suggest an early period of deformation, 2) Pervasive schistosity and mineral lineation associated with isoclinal folding and greenschist-lower amphibolite facies metamorphism have led to extreme transposition of bedding; deformation and metamorphism increase with proximity, and are apparently related, to the Baboquivari Thrust Fault, a major thrust emplacing Jurassic plutonic rocks over the metamorphic rocks described above, 3) Locally developed post metamorphic crenulation lineation and cleavage are generally associated with small, open, upright folds in the older foliation, 4) All older features are locally deformed about the latest Cretaceous-early Tertiary garnet two-mica Presumido Peak Granite, and 5) metamorphic core complex type deformation has affected the Presumido Peak Granite near the border with Mexico.
- Research Organization:
- Univ. of California, Berkeley (USA)
- OSTI ID:
- 6863828
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARIZONA
METAMORPHIC ROCKS
GEOLOGIC HISTORY
PETROGENESIS
PETROLOGY
TECTONICS
DEFORMATION
GEOLOGIC FAULTS
METAMORPHISM
MOUNTAINS
OROGENESIS
FEDERAL REGION IX
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
NORTH AMERICA
ROCKS
USA
580100* - Geology & Hydrology- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580201 - Geophysics- Seismology & Tectonics- (1980-1989)