Detrital Modes of Selected Sandstone Samples from the McCoy Mountains Formation and Correlative Units in Southwestern Arizona

Previous workers have established the general petrological character of the McCoy Mountains Formation and equivalent Jurassic-Cretaceous units in southwestern Arizona and southeastern California by point-counting the detrital modes of 170 sandstones and metasandstones (Robison, 1979; Harding, 1980, 1982; Harding and Coney, 1985; Laubach et aI., 1987; Richard et aI., 1987; Fackler-Adams et aI., 1997). Many of the samples studied, however, are foliated to varying degrees, with neomorphic growth of metamorphic minerals partly obscuring detrital textures and compositions. For this report, a set of control samples was collected from the least deformed and least altered rocks that could be found exposed in mountain ranges of southwestern Arizona.