Bisbee daily review., 1904-02-13
tcoutinuei From Page Two,
TIE GEOLOGY AND COPPER
 FORMATION OF ARIZONA

bees and have far more complicated structure. Their degradation has consequently resulted in a more rug ged and less regular topography.
 The PreCambrian Basemeat.-The rocks forming the PrelCambrian basement, the oldest rocks known in She Mule mountains, are fine grained sericite schist. derived from the an cient sediments. These, which have been called the Pinal schists, were propably original shades or arkose sandstones, which were folded and Eetamorphosed into their present crystalline condition before Cambrian time.
 The Palezoic Sedimentary Series Alter long erosion the Pinal schists were reduced to a surface Of very slight relief. which in Cambrian time was submerged beneath the sea and covered with sands that are now rep resented by the Bolsa quartzite (Cam- erian), from 400 to 800 feet in thick ness. The Bolsa quartzite has at its base a thin conglomerate. which rests with unconformity upon the eroded edges of the Pinal schists.
 The sa5mergence of the area con tinred, and about 750 feet of thin bedded, cherty, fossiliferous Middle Cambrian iimestones named the Abri- go limestone. accumulated on top of the Bolsa Quartzite. No record of SiiuriaI time has been discovered in the Bisbee quadrangle. Overlying the Abrigo limestone, apparently in perfect conformity, are $40 feet of dark-coiored. compact. rather thin bedded limestores, with some inter calated shales. all carrying an abund- ant and characteristic Devonian fau- na. consisting chiefly of brachiopods and corals. This formation Is dis tsnguished as the Martin limestone.
 The opening of Carboniferous time interruption of the continued subsid- ence. No unconformity has been de- cected between the Devoian and the lower Carbcniferous (Mississippian) rocks. The latter consists Of whits or light-gray granular limestones, of ten made up almost entirely of crinoid limestone may be provlsionally given as 700 feet The beds are often six feet or more in thickness. and con- monly form cliffs overlooking slopes carved from the less resistant Devo- Hian and Cambrian limestones. This formation has received the name of the Escabrosa limestone.
 There is in the Mule mountains no discoverable stradgraphic break be tween the lower and upper Carbonif- ercus beds Subsistence apparently continued, and the generally thinner beds of upper Carboniferous (Penn- eylvanian) limestone accumulated to a thickness of over 5000 feet above the lower Carboniferous. The upper Carboniferous limestones are usually more compact in texture than those of the lower Carboniferous, and are rrore fossiliferous. They are also somewhat more variable in color, pinkish and yellowish becs of ire euent occurrence. This formation has been named the Naco limestone.
 The local Paleozoic section from the Pinal schists very nearly to the top of the Ncabrosa limestone IS well ev- posed on the northeast face of Esca- brosa ridge. about Is miles west cf Bisbee. The beds of the Naco lime stone are best seen in the hills just north of Naco Junction 6 miles south vest of Bisoee). and the comfortable relation between the Escabrosa and Naco iimestones is well. shown near the Whitehall mountains, about 7 miles due south of Bisbee.