320 ROLLIN T. CHAM BERLIN 



"incontestable evidence of discordance along its whole length."^ 

 The fossiliferous Silurian slates are marked by a heavy basal con- 

 glomerate whose pebbles have been derived from the Cambro- 

 Ordovician strata, but it is not clear how much time is represented 

 by the unconformity. 



The width of the belt affected by the movement may have been 

 considerable. In southern Quebec, southeast of the St. Lawrence 

 River, isolated areas of Silurian strata, largely limestones, occur in 

 some of the synchnes, and these Silurian beds are found to lie 

 unconformably upon Ordovician strata, indicating that this region 

 also was affected by the movement.^ But the effects of the uplift 

 were not felt upon the north side of the Gulf of St. Lawrence, for 

 on Anticosti Island the accumulation of the great limestone forma- 

 tion which commenced in Ordovician times continued without a 

 break into the Silurian.^ 



From the region of the Taconic Mountains of New England and 

 New York evidences of this uplift may be traced south westward. 

 What appear to be evidences of the same disturbance have been 

 noted on the east side of the Appalachian Mountains as far south as 

 Virginia.'' In 1892 , N. H. Darton found some crinoids, which Walcott 

 has assigned to the Upper Ordovician, in the slate quarries at Arvon, 

 in the Piedmont region of Virginia. ^ While the age of the deforma- 

 tion and metamorphism of these rocks is not established, Dana 

 nevertheless regarded this strip as possibly a part of a long West- 

 chester Taconic range which passed just west of Philadelphia and 

 Baltimore.^ Very possibly also a portion of the folding of early 

 Paleozoics in New Jersey may belong to the Taconic movement. 

 But here again the age of the folding has not been definitely placed. 



I L. W. Bailey, in G. M. Dawson's Summary Rept., Geol. Survey of Canada, XIII 

 (1900), 146-48 A. 



^ R. W. Ells, cited by Willis, "Index to the Stratigraphy of North America," Pro/. 

 Paper 71, U.S. Geol. Survey (1912), p. 250. 



3 W. B. Scott, An Introduction to Geology (1907), p. 567. 



1 M. R. Campbell, "Paleozoic Overlaps in Montgomery and Pulaski Counties, 

 Virginia," Bull. Geol. Soc. Am., V (1894), 189. 



s N. H. Darton, "Fossils in the 'Archean' Rocks of Central Piedmont Virginia," 

 Am. Jour. Scl., 3d Ser., XLIV (1892), 50-52. 



* J. D. Dana, op. cit., p. 532. 



