160 abstracts: geology 



gneiss, dikes, mineral veins, contacts, etc. At the end of Part II, which 

 is economic in character and is by Dale, the commercial granites of Con- 

 necticut are divided into 10 petrographic groups including 20 well- 

 defined varieties. T. N. D. 



GEOLOGY.— Geologic atlas of the United States, Folio No. 175. Bir- 

 mingham (Alabama) Folio. Charles Butts. Maps and sections. 

 1911. 



The Birmingham folio deals with an area of 1000 square miles. The 

 broad surface features are the Birmingham and the Cahaba anticlinal 

 valleys, with the low synclinal plateaus of the Chaba, Coosa, and Blount 

 Mountain coal fields, with northeast-southwest trend, in the southeast- 

 ern part; and the low plateau of the Warrior coal field in the north- 

 western part. The deeply dissected upland surfaces are probably rem- 

 nants of the Cumberland plateau or peneplain (Schooley?), and the 

 valleys may represent the Coosa peneplain. 



The geologic section is as follows: Pottsville formation 2300-5100 

 feet; unconformity; Parkwood formation (new, Mississippian), shale and 

 sandstone 200-2000; Pennington shale and Bangor limestone to north- 

 west-Floyd shale to southeast, 1000 feet; Fort Payne chert 250 feet; 

 unconformity; Chattanooga shale 20 feet; unconformity; Frog Moun- 

 tain sandstone (Oriskany) ; unconformity (Helderbergian, Cayugan, and 

 Niagaran absent) ; Clinton formation, sandstone and shale, with fossil- 

 iferous ore beds, 250-500 feet; unconformity (CincinnatianandMohawk- 

 ian absent); Chickamauga limestone (mainly Chazyan) 200-450 feet; 

 unconformity (Canadian absent in Birmingham valley) ; Knox dolomite, 

 Ketona dolomite (new name) at base 3300 feet; uncomf ormity ; Cona- 

 sauga limestone 2000 feet; unconformity; Rome formation 500 feet. 



The rocks are folded and faulted in the southeast and nearly flat in the 

 northwest. The Warrior and Cahaba coal fields are bounded on the 

 east by thrust faults, with displacement of 8000 to 10,000 feet, bringingthe 

 Cambrian into contact with the Pottsville. Minor thrust and normal 

 faults occur also. 



The principal mineral resources of the quadrangle are (1) coal, (2) 

 iron ore, (3) limestone and dolomite, (4) shale, and (5) clay. The close 

 association of the first three is the chief factor in the industrial promi- 

 nence of the region. In the Warrior field are eight, and in the Cahaba 

 field are two or more workable coal beds. 



The iron ore is hematite, called red "fossil" ore on account of the abun- 

 dant fossil shells which make it very calcareous. The weathered or 

 "soft"' ore carries 55 per cent metallic iron and 0.5 per cent lime, and the 



