SYSTEM OF BATHOLITHS 321 



basins parallels that of the Paleozoic folds in a striking manner as far 

 as the Triassic beds are known, and the Triassic faults extend far beyond 

 the Triassic sediments with trends parallel to the Appalachian structure. 

 The Triassic trends plainly show the Virginia and New York recesses 

 and the Pennsylvania salient, but the Triassic beds do not reacli! far- 

 enough to exhibit the northern Vermont or northern Georgia salients. 

 As far as they at present extend, however, the- correspondence of the 

 Triassic and Paleozoic trends is so complete that they must have a cause 

 or a factor in common. Inasmuch as the Triassic basins and structures 

 are directly controlled by the trends and vertical movements of the base- 

 ment (mainly Precambrian rocks), we can hardly escape the conclusion 

 that this same control was exercised on the Paleozoic movements by the 

 Precambrian basement. Thus the three factors, (1) divergence of Pre- 

 cambrian structures, (2) control of Triassic structure by Precambrian, 

 (3) parallel trends of Paleozoic and Triassic structures, combine to show 

 the dominant influence of the Precambrian basement on all the struc- 

 tures of the Appalachian region. Even in the Tertiary and Pleistocene 

 deformations the general axis of uplift is roughly the same as for the 

 Precambrian, Paleozoic, and Triassic. This is precisely what should 

 have been expected; if the Precambrian rocks were so distributed or of 

 such a nature as to exercise a control during one epoch, the same factors 

 would tend to produce it at later epochs. 



SYSTEM OF BATHOLITHS 



A matter of prime importance in the distribution of the various facts 

 of the Appalachians is that of the intrusive masses, or batholiths. A 

 generalized mapping of these for the southern Appalachians was given 

 by the author on the geologic map of North America,^ and large numbers 

 of them have been mapped by various geologists in New England and 

 the eastern provinces of Canada. In the southern Appalachians the 

 batholiths, mainly granites, extend across Georgia, North Carolina, and 

 South Carolina. They are found for the most part in the Piedmont, and 

 only in North Carolina and northern Georgia do they occur wTst of the 

 Blue Eidge. There is a decided predominance of the batholiths in South 

 Carolina, behind the North Carolina salient, and they barely reach the 

 Alabama-Georgia recess. They are of late Carboniferous age, since they 

 are deformed little or not at all by the Carboniferous deformation. On 

 the Pennsylvania salient the Piedmont belt is very narrow, but a few 

 batholiths of Carboniferous age appear. Northward from the New York 



- TJ. S. Geol. Survey, Prof. Paper No. 71. 



