o22 A. KZITH .jUTLIXES OF AFFALACHLO.' STRrCTUKE 



recess CarboniferoTis batholiths are mmierous. In Massaeimsetts. Xew 

 Hampshire, and aoutlieni Maine they cut Carbonif erons rocks, and there 

 is a considerable c-oncentration of them in southern Maine and the White 

 Mountains of Xew Hampshire back of the northern Vermont salient. 

 In eastern Maine and Xew Brunswick similar batholiths are nttmerons 

 .and have been assigneii to the Devonian bec-ause they cut Devonian rocks 

 .and are overlain by Carboniferous. These are situated behind the north- 

 ern or Gaspe salient. The chief poinrs of distribntion of these batholiths 

 are their concentration behind the great salients and their chief develop- 

 ment in the northern and sonthem parts of the Appalachian chain, where 

 deformation by shortening is demonstrably the gTearest. The meaning 

 ■of this will be 'iiscnssei on later pages. 



PRECAJlBRIAy PLATEAU 



The broad belt of Ktde folded rocks which nnderlies the Appalachian 

 plateaus and the Saint Lawrenc-e Valley is a distinct tmit of the Appa- 

 lachian system. As has already been stated, the eastern boundary of the 

 little folded belt is distinct as a whole in the s«jiLthwestem and north- 

 eastern parts of the system, but is less so in Pennsylvania and West Vir- 

 ginia. *!>nlside of these States the boundary is so sharp as to challenge 

 explanaiiin. In Xew Y jik and Canada the answer is not hard to find. 

 The closely folded belt is oc-cupied by a thick section of Lower Cambrian 

 3^d AlgonMan beds, while in the gently folded belt they are absent and 

 the section shows mainly a t hi n development of Ortlovician. In the Saint 

 XAwrenc-e Valley in s<3uthem Ontario and Quebec these se<iiments are 

 nearlv Jiat. Thev rise to the south and from beneath them emersres the 

 plateau developed on Prec-ambrian granites and gneisses. The rise of 

 the Prec-ambrian in this Adirondack dome is c-aused by one of the major 

 cross-antielines. and on its south side in the same way the Precambrian 

 rocks of the A«iiron«iacks pass beneath the Ordovician. Xorth of the 

 Saint Lawrenc-e Valley the same general Prec-ambrian plateau exists, 

 and on it overlap the L«jwer t>rdovician strata. This plateau at the base 

 of the Paleozoic was re<iuceii to a very even surface and doubtless was of 

 correspondingly broad extent. The extension southward of this relation 

 is thus more than probable through southern Xew York into Pennsvl- 

 vania. In fact, the boundary between the sharply folde<i and little folded 

 rocks is very plain in the lower Mohawk Valley and connects the eastern 

 margin of the Catskills. 



Viewing the little folded and the much folded sections of the valley 

 with respect to the rigi«iity of their respective strata, it is particularly 

 clear that the thin Ordovician section supported by massive Precambrian 



