308 THE CAMBRIAN. Lbull.81. 



In a report on the geology of the Cahaba Coal Field Prof. Eugene A. 

 Smith describes the Cambrian rocks as they occur in the Coosa Valley 

 of northeastern Alabama. The maximum thickness given is 10,000 

 feet in the eastern part of the Coosa Valley. The subdivisions of the 

 Cambrian recognized are, in ascending order, as follows: "The Coosa 

 shales, the Choccolocco or Montevallo shales, and, interbedded with 

 the last named, the Weisner quartzite. m 



The Coosa shales are described as thin-bedded limestones with clay 

 seams at the base, and pass above "into the Montevallo shales, 

 which form a considerable thickness of sandy shales of a great 

 variety of colors, such as olive, green, brown, chocolate, yellowish, 

 etc. In the upper part of the Montevallo shales beds of blue limestone 

 and gray dolomite occur which are difficult to distinguish from similar 

 rocks occurring in the superjacent dolomite series. Lenticular masses 

 of quartzite many hundreds of feet in thickness occur in the Montevallo 

 shales. This quartzite is named the Weisner quartzite from its typical 

 locality at Weisner Mountain, east of Jacksonville, and is correlated 

 with the Chilhowee formation of Prof. Saiford in Tennessee. 2 



From our present knowledge of the formations referred to the Cam- 

 brian in Alabama it appears that they are the continuation of those re- 

 ferred to the same group in Georgia and Tennessee, though varying 

 somewhat in the local details of sedimentation, thickness of beds, and 

 lithologic characters. 



The section of Mr. C. Willard Hayes, described under Georgia, em- 

 braces much of the Cambriau strata that passes into Alabama, and 

 should be referred to in this connection. (Ante, p. 304.) 



r£sum£. 



For a distance of over 1,200 miles the pre-Cambrian lands formed the 

 eastern boundary of this province during the deposition of the sediments 

 of Cambrian time. From below Montreal to the foot of Lake Champlain 

 and thence southward to the crossing of the Hudson, below Pough- 

 keepsie, New York, and on across New Jersey, Pennsylvania, Virginia, 

 Tennessee, and into Georgia and Alabama, the rocks of this pre-Cam- 

 brian laud form an almost continuous outcrop at the present day. The 

 Cambrian rocks extend 400 miles farther to the northeast from Quebec 

 to the northern portion of the peninsula of Gaspe ; but there is now an 

 interval of over 200 miles between the Archean ridges of eastern Quebec 

 and the long, narrow Archean axis of the GaspC peninsula. The ex- 

 posures of the Cambrian on the coast of Labrador, opposite the Straits 

 of Belle Isle, and those of the west shore of Newfoundland, have been 

 included in the Atlantic Coast Province, but they are quite as much a 



'Geological structure and description of the valley region adjacent to the Cababa Coal Field. Geol, 

 Survey of Alabama. Report on the Cahaba Coal Field, pt. ll, 1890, p. 148, (issued January, 1891). 

 2 Op. cit., pp. 148, 149. 



