Mylonitic fabrics in the eastern Santa Catalina Mtns, Arizona

Jon Spencer (formally Sr. Geologist at AZGS) and Kurt Constenius have a new technical report, Reconnaissance study of mylonitic fabrics in the Bellota Ranch area, eastern Santa Catalina Mountains, Arizona, just released and downloadable at the AZGS Document Repository.

From the report abstract, "The 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 12-page Contributed Report is accompanied by an annotated 9-slide powerpoint presentation illustrating mylonitic textures at the hand specimen scale.

CITATION.  Spencer, 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.