No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

In the Colossal Cave area, Pima County, Arizona, massive blocks of Paleozoic sedimentary rocks have been thrust from a southerly direction over an irregular surface of Rincon Valley granite of Laramide age. The Paleozoic rocks involved in the thrusting are the Bolsa quartzite, Abrigo formation, Martin limestone, Escabrosa limestone, Horquilla limestone, and Andrada formation. The Pantano formation (Miocene ?) is also present under the thrust sheet. The thrusting is of an imbricate nature with slip-page mainly teaking place along incompetent rock units. Large folds occur in the Escabrosa limestone and Horquilla lime-stone. A siliceous breccia is associated with thrust planes in the area. The competent units of the Paleozoic sediments were fractured and brecciated along the thrust planes. Solutions dissolved part of the silica and hematite from the Bolsa quartzite and deposited it in the fractured and brecciated zones.

Mildly metamorphosed Cretaceous siltstones, arkoses and limey shales and a small composite stock of granitic composition are the principal rocks exposed in the Sedimentary Hills area, which lies six miles west of Tucson, Arizona. About 2400 feet of sediments were measured and assigned to the Amole Arkose Formation. The beds dip to the south and strike northwesterly. The stock is composed of two granitic facies. The northern and earlier part of the stock is a quartz monzonite which is mildly altered. The southern part of the intrusive is a granite porphyry which is altered to a greater degree and exhibits significant disseminations of chalcopyrite and pyrite. A quartz-pegmatite plug, probably a late phase of the intrusions, intrudes the quartz monzonite. Structure in the area is dominated by a large thrust zone which strikes generally parallel to the bedding. Within the Sedimentary Hills area, normal faulting and drag folding are tributary to the thrusting. Minor copper oxide minerals are frequent along large and small faults, and in the granite porphyry stock. Wide brick-red and brown gossans occur along the major thrust plane.

No description available.