Pg. 739-740, pl. 1. Safford dacite. Consists of three varieties of rock: fresh porphyritic dacite with groundmass of minute spherulites; porphyritic border facies with clear glass groundmass; and chalky porphyritic dacite. Chalky white to light gray when fresh and gray to light drab on weathered surfaces. Flow structure nearly vertical and parallel to its borders. The dacite pierces the Rillito andesite (new) and the Safford tuff (new). The mass is regarded as an eroded volcanic neck. Age is Tertiary.
Largely confined to core of Safford Peak [in E/2 sec. 31, T. 12 S., R. 12 E., Lat. 32 deg. 20 min. 43 sec. N., Long. 111 deg. 09 min. 00 sec. W., Avra 7.5-min quadrangle], Tucson Mountains, Pima Co., southeastern AZ. Area of peak is elliptical, the long axis of which is 2,800 ft and short axis is 1,500 ft.

Source: US geologic names lexicon (USGS Bull. 1200, p. 3377).

Replaces compositionally and genetically related dacitic units previously designated Rillito andesite (abandoned), Safford formation, Safford tuff, upper andesite, and Safford neck by Brown (1939) and Bikerman, Damon (1966, GSA Bull., v. 77, p. 1225-1234) in Tucson Mountains, Pima Co, AZ, Basin-and-Range province. Safford is remnant of small volcanic field in northern part of Tucson Mountains. Consists of lava flows, vent intrusions, vent spatter, and volcaniclastic deposits consisting of tuffaceous rocks and mudflow deposits. Individual lava flows are 25-100 m thick; four flows are preserved at Safford Peak; K-Ar biotite ages are 39.5 Ma (may be anomalously old) for oldest flow (flow 1) to 25.1 Ma for youngest flow (flow 4); 40Ar/39Ar biotite age for flow 1 is 26.6 Ma. Vent necks, occurring on Safford Peak and south of Panther Peak, were probable feeder for flow 4. Vent spatter of intermixed black glassy and red-brown devitrified agglutinated dacitic rock occurs at head of Sunset Road; vent location concealed beneath alluvium. Tuffaceous rocks are up to 20 m thick; K-Ar age of 25.9 +/-1.4 Ma. Mudflow deposits consist of red-brown indurated conglomerates, containing rounded clasts of dacitic lavas of Safford Peak up to 0.5 m in diameter; up to 50 m thick along ridge between Panther and Safford Peaks. Older than Quaternary surficial deposits; younger than rocks of Tucson Mountain caldera cycle (which includes Cat Mountain Tuff). Assigned Oligocene age.

Source: GNU records (USGS DDS-6; Denver GNULEX).