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dc.contributor.authorSpencer, J.E
dc.contributor.authorConstenius, K.N.
dc.date.accessioned2020-08-06T22:12:00Z
dc.date.available2020-08-06T22:12:00Z
dc.date.issued2020
dc.identifier.citationSpencer, J.E. and Constenius, K.N., 2020, Reconnaissance study of mylonitic fabrics in the Bellota Ranch area, eastern Santa Catalina Mountains, Arizona. Arizona Geological Survey Contributed Report CR-20-C, 12 p, one appendix.en_US
dc.identifier.urihttp://hdl.handle.net/10150/642094
dc.descriptionThe Santa Catalina Mountains in southeastern Arizona include extensive mylonitic fabrics developed within granitic and gneissic rocks that make up most of the range. These fabrics are strongest at the southern foot of the range where they dip south and project beneath the rangebounding Catalina – San Pedro detachment fault. Shear sense in the mylonitic rocks is primarily top-southwest, consistent with shearing down-dip from the detachment fault during early normal faulting and exhumation to form the metamorphic core complex. Two to three kilometers north of the foot of the Santa Catalina Mountains the mylonitic foliation is horizontal and farther north it dips to the north. The mylonitic fabrics thus dip outward from the axis of the Forerange arch with primarily top-northeast shear-sense indicators on the north side of the arch. This dominantly topnortheast fabric forms the Molino Basin shear zone, which continues eastward toward the Bellota Ranch area that is the subject of this study. We found that mylonitic fabrics in the Bellota Ranch area are generally subhorizontal, weak, and without clear shear-sense indicators in by far ost outcrops. Four days of field study yielded clear shear-sense indicators at only eight outcrops, with six of them indicating top-southwest shear sense. We were not able to divide mylonitic rocks into top-southwest and top-northeast zones as in a previous study by Bykerk-Kauffman (2008). Lineation trend gradually changes laterally from more northeasterly in the Molino Basin area to more northerly in the Bellota Ranch area. As with the Molino Basin area, lineations associated with top-northeast shearing generally trend more northerly than lineations associated with top-southwest shearing. We conclude that mylonitic lineation in the Bellota anch area is not a simple continuation of the Molino Basin shear zone as it is dominated by top-southwest shear-sense indicators rather than top-northeast as with the Molino Basin shear zone.en_US
dc.language.isoenen_US
dc.publisherArizona Geological Survey (Tucson, AZ)en_US
dc.relation.ispartofseriesCR-20-Cen_US
dc.relation.urlhttp://repository.azgs.az.gov/uri_gin/azgs/dlio/1951en_US
dc.rightsArizona Geological Survey. All rights reserved.en_US
dc.subjectArizona Geological Survey Contributed Reportsen_US
dc.subjectMetamorphicen_US
dc.subjectcore complexen_US
dc.subjectdetachment faulten_US
dc.subjectgneissen_US
dc.subjectmyloniteen_US
dc.subjectBellota Ranchen_US
dc.subjectMolino Basinen_US
dc.subjectPima Countyen_US
dc.subjectRincon Mountainsen_US
dc.subjectSan Pedro River Valleyen_US
dc.subjectSanta Catalina Mountainsen_US
dc.subjectCenozoicen_US
dc.subjectMioceneen_US
dc.subjectProterozoicen_US
dc.subjectTertiaryen_US
dc.titleReconnaissance study of mylonitic fabrics in the Bellota Ranch area, eastern Santa Catalina Mountains, Arizonaen_US
dc.contributor.departmentArizona Geological Surveyen_US
csdgm.bounding.west-110.786en_US
csdgm.bounding.east-110.556en_US
csdgm.bounding.north32.5168en_US
csdgm.bounding.south32.3476en_US
dc.description.collectioninformationDocuments in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu.en_US
refterms.dateFOA2020-08-06T22:12:10Z


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