EARLY DEVONlC HISTORY OF NEW YORK AND EASTERN nORTH AMERICA 99 



to the circumpolar shield ; the plication that followed brought up at the 

 north the next later deposits present in this section (" Cambro-Siluric ") 

 the different series being entirely unconformable. We have elsewhere 

 recorded the evidence which indicates that dark shales are the deposits of 

 considerable oceanic depths, a view confirmed by the course of reasoning 

 adopted by Haug and others. It is, therefore, justifiable to conclude that 

 in any normal geosyncline the first plications, being the upfolding of the 

 deepest sediments, will be presumably constituted of dark shale beds. The 

 Gaspe depression exemplifies this procedure in the upturning of its primary 

 folds. Then at the north followed, during a long period, the subaerial 

 erosion of these unconformable and highly plicated east and west folds, the 

 younger being worn away from above the older and leaving this latter 

 exposed today along a zone south of the former. Thereafter was a period 

 of rest and active deposition in the geosyncline that ensued before the 

 renewal of plication. Fifteen hundred or more feet of limestones had been 

 laid down in the shallowing depression and then by abrupt change in drain- 

 age and in part through locking out of the sea by distant barriers some 

 thousands of feet of sand and conglomerates followed one on the other all 

 in essential conformity. 



The limestone as well as the sands are the indication of lessened 

 depth, of deposits shoreward of the shale-mud banks and raised above the 

 level of the primary line of weakness and folding ; hence they constitute 

 only secondary plications along the geosynclinal depression. 



During this vast period of quietude the geosynclinal area of deposition 

 had narrowed by elevation at the north of the primary folds, but we have 

 shown that the colored Devonic limestones about Perce though then still 

 lying flat on undisturbed earlier sediments were brought so near to the sur- 

 face, as to receive none of the deposits of the lower Gaspe sandstone which 

 were laid down on them at the north. It was really but a slight epirogenic 

 change here that shifted the calcareous muds into the lagoon conditions 

 which led to the deposition of the Gaspe sandstones conformably upon them. 



The geosynclinal deposits at the south involving the Perce Devonic 



