DIASTROPHISM AND THE FORMATIVE PROCESSES 319 



In North America the disturbances occurred principally on the 

 eastern side. A portion of the Atlantic border was strongly folded. 

 According to Campbell, the general region lying eastward from what 

 is now the Appalachian Valley, throughout much of its extent, was 

 subject to disturbing influences at several periods during the Paleo- 

 zoic.'' This is in accord with the view that the source of the vast 

 quantity of clastic sediment which was laid down in the Appalachian 

 geosynchne in the course of the Paleozoic was the old land of 

 Appalachia lying between the present mountains and the edge of 

 the continental shelf. So great a volume of the sediments derived 

 from this not very extensive land area is thought to imply a repeated 

 renewal of the land by uplift. 



Definite evidence of one such disturbance is found in the Taconic 

 Mountains of western New England and the adjacent portions of 

 New York and Canada. In this region the Cambrian and Ordovi- 

 cian strata are sharply folded and faulted while the Silurian strata 

 rest unconformably upon the flanks of these folds and are not 

 incorporated in them.^ Today only the obscure stumps of these 

 ancient mountains are visible, but they seem once to have consti- 

 tuted a great range. Thrust faulting, not unlike that of the south- 

 ern Appalachians, was prominent but perhaps on a somewhat 

 smaller scale. ^ 



This ancient chain of mountains extended far to the northeast, 

 paralleHng the present coast. A large tract in northeastern Maine, 

 northwestern New Brunswick, and the Gaspe Peninsula is occupied 

 by a broad synclinorium of Silurian strata which appear to He 

 unconformably upon folded and eroded Cambrian rocks."* From 

 Maine the eastern margin of the Silurian extends northeastward 

 across New Brunswick to the Bay of Chaleur. In surveying the 

 line between the Cambro-Ordovician and the Silurian, Bailey found 



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

 Virginia," Bull. Geol. Soc. Am., V (1894), 178-79. 



2 James D. Dana, Manual of Geology, 4th ed. (1895), p. 386. 



3 C. D. Walcott, "The Taconic System of Emmons," Am. Jour. ScL, 3d Ser., 

 XXXV (1888), 315-20; James D. Dana, op. cit., p. 528. 



* L. W. BaUey and WiUiam Mclnnes, "Explorations in New Brunswick, Quebec 

 and Maine," Ann. Rept. Geol. Surv. Canada, New Ser., Ill (1889), 29-31 M. 



