194 INDEX TO THE STEATIGEAPHY OF NORTH AMERICA. 



In the same monograph Pumpelly *^* describes the structural and stratigraphic 

 grounds for correlating the Cambrian and Ordovician strata of Mount Greylock 

 with the Hoosac schist on the east. The latter is mapped as Cambrian and Ordo- 

 vician. (See Chapter III, p. 114.) 



In southwestern Massachusetts and adjoining parts of Connecticut and New 

 York lies the Mount Washington mass of the Taconic Range, which has been more 

 particularly studied by Hobbs,*^® who distinguished four formations apparently 

 equivalent to those recognized by Dale, namely: 



Mount Washington, 110111)3. 



Mount Greylock, Dale. 



Top. 



Everett schist 



Egremont limestone 



Kiga schist , 



Canaan dolomite 



Greylock schist. 

 Bellowspipe limestone. 

 Berkshire schist. 

 Stockbridge limestone. 



Ordovician strata, which, though highly metamorphosed by igneous injection, 

 are identified as representatives of the Stockbridge dolomite and "Hudson shale," 

 form part of Manhattan Island, New York.^^^ They have been traced through 

 eastern New York and western Connecticut to the fossiliferous area of the Taconic 

 Range, first by Dana, and later by Gregory.^^ 



L 12. SOUTHWESTERN MONTANA. 



There is no recognized break in the sequence of lower Paleozoic strata which 

 appear around the uplifts of southwestern Montana; and yet no strata which may 

 certainly be referred to the Ordovician are known there. Apparently but slight 

 record of marine or land conditions was made in the region during that long time. 



L 16. UPPER PENINSULA OF MICHIGAN. 



Rominger *"" describes in detail the occurrence of " Chazy and Calciferous, 

 Trenton, and Hudson River" strata in the Upper Peninsula of Michigan. The dis- 

 tribution of the formations as shown on the map of North America is taken from 

 the geologic map of Michigan published by the present Survey, and the following 

 notes are abstracted from a paper by Lane.^^^ 



Lane describes in ascending order St. Peter sandstone, Trenton limestone, 

 Utica shale (Eden of Ohio) , and Lorraine or Maysville shale as formations composing 

 the Ordovician between the "Calciferous" and his "Richmond and Medina transi- 

 tion beds." 



The St. Peter sandstone does not outcrop in Michigan but is recognized in well 

 drilling as a quartz sand between the "Trenton" limestone above and the "Calcif- 

 erous" limestone below. Its thickness is very irregular, presumably because it 

 lies on an uneven surface. 



The "Trenton" of northern Michigan, according to Lane and Grabau, com- 

 prises the equivalents of the Chazy, Black River (LowviUe or "Birdseye" and Black 

 River of present usage), and Trenton of Hall's classification in New York, or the 

 Chazy and Mohawkian of the present New York State Survey classification. The 

 base of this limestone is the passage into the St. Peter sandstone, or, where that is 



