THE BASIN PROVINCE 119 



gray, sometimes slightly pinkish, crinoidal limestones, usually in rather thick 

 beds, but also some cherty beds and an occasional bed of siliceous conglomerate." 



The lower part of this limestone is regarded as Mississippian and the 

 upper part as Pennsylvanian. On page 109 Ransome states: 



"From the Devonian to the Upper Carboniferous the region was covered by 

 a sea of some depth abounding in marine Hfe and depositing abundant limestone. 

 Although no characteristic Lower Carboniferous fauna was found, rocks of that 

 period may be present, and the Globe limestone as a whole contains no visible 

 unconformities. From time to time there were slight incursions of sediment, 

 and in a few instances bands of siliceous conglomerate were intercalated within 

 the limestones. The mass of these is unimportant, but they are significant in 

 showing that this part of the Devonian and Carboniferous sea was probably 

 neither very deep nor far distant from a land-mass. 



"The Upper Carboniferous limestone is the latest Paleozoic deposit of which 

 the region preserves any record. If marine conditions continued into the Permian 

 the deposits of that period must have been wholly removed before the strata 

 were broken up and invaded by diabase. Had Permian or later beds been 

 involved in that structural revolution some traces of them would probably have 

 been preserved in the resulting intricate lithological mosaic. * * * The region 

 was presumably elevated above sea-level at the close of the Carboniferous and 

 subject to erosion." 



[The Clifton-Morenci district in Arizona shows] "at least 500 feet of heavy- 

 bedded bluish-gray limestone which unquestionably represents both the Missis- 

 sippian and the Pennsylvanian. In a general way the lower 200 feet are equiva- 

 lent to the Modoc formation, although its several members recognized farther 

 south can not be identified, and the upper 300 feet represent the Pennsylvanian. 

 It is not possible, however, to draw a dividing line, and the whole therefore has 

 been included in the single formation named the Tule Spring limestone. * * *" ^ 



"Above the Morenci shales, ^ in a deepening sea, were deposited a series of 

 limestones, first dolomitic, then remarkably pure and rather coarse, the Modoc 

 and Tule Spring limestones of the Mississippian and Pennsylvanian epochs. 

 Throughout the whole of the Carboniferous animal life was abundant and rich 

 faunas may be collected in many places." 



The Pennsylvanian beds are cut off by the erosion face of a great un- 

 conformity. 



In the Fort Apache, Arizona, region, according to Reagan,^ the upper- 

 most beds belong to the Aubrey group : 



"The interstream spaces of all the streams in their upper course as well as 

 the south front of the Mogollon Range and the Cibicu Divide, where not covered 

 with later deposits are capped with 280 feet of calcareous sandstone followed by 

 500 feet of soft red and gray shales, interrupted by sectile limestone. The 

 Aubery (Kaibab) limestone occurs in one locality — at the head waters of the 



^ Lindgren, W., Description of the Clifton Quadrangle, Folio 129, U. S. Geological Survey, 



P- 5- 1905- 

 ^ Idem, p. II. 

 ^ Reagan, A. B., Geology of the Fort Apache Region in Arizona, Amer. Geol., vol. xxxii, 



p. 280, 1903. 



