NEWFOUNDLAND APPALACHIANS 



221 



Ultramafic Intrusions 



A zone of serpentinized ultramafic intrusions extends from Georgia 

 through the crystalline Piedmont to New York City, and from New York 

 northward through the Taconic system to the St. Lawrence and Gaspe. 

 From there it is believed to continue through western Newfound- 

 land. 



Fronts of Successive Orogenies 



An attempt was made by Schuchert in his early paleogeographic maps 

 and later by Schuchert and Dunbar ( 1934 ) to show the major structural 

 elements of Greater Acadia. They postulated a western trough of sedimen- 

 tation, the St. Lawrence geosyncline; a central land barrier, the New 

 Brunswick geanticline; and eastern trough of sedimentation, the Acadian 

 geosyncline; and beyond this, a borderland, Novascotica. As described 

 on previous pages, the "New Brunswick geanticline" has been found to 

 be approximately the heart of the geosyncline — a site of such sedimenta- 

 tion and prodigious igneous and orogenic activity. Crustal movements 

 within the orogenic belt were numerous, and the island barriers and pen- 

 insulas were too many and transitory to be charted satisfactorily with 

 present knowledge. 



Kay (1947) has illustrated the Taconic, Acadian, and Appalachian 

 orogenic systems of Greater Acadia to have been formed by deforma- 

 tion of the sediments of the eugeosyncline. This great sedimentary 

 province includes the volcanic assemblages of sediments, the batholiths 

 and serpentinites, in contrast to the relatively igneous-rock-free inner mio- 

 geosyncline typified by the sediments of the Bidge and Valley province. 

 It is clear that the belts of deformation of the eugeosyncline impinge on 

 the Canadian Shield in the Greater Acadia region, and that the belt of 

 deformation of the inner miogeosyncline terminates approximately at the 

 Adirondacks. 



Some progress can be made toward an understanding of the spatial 

 relations of Greater Acadia if the distribution of the orogenic belts is 

 charted, rather than the poorly documented and transitory shore lines. 

 The fronts of the Taconic, Acadian, and Appalachian orogenic belts are 



known in places with considerable precision and in others only approxi- 

 mately. Figure 13.12 shows these fronts, as well as the zones of superposi- 

 tion of one belt over the other. Evidence of the locations for the most part 

 has already been presented, and when composed for the entire Greater 

 Acadia, yields the picture recorded on the map. In the lower left-hand 

 corner, the northern end of the Appalachian folded and thrust-faulted belt 

 of the Valley and Bidge province is seen. The Taconic front then faces the 

 shield (with its thin sedimentary veneer). At Quebec City on the St. Law- 

 rence, the front of the Acadian orogenic belt impinges on the shield, and 

 as far as known from Quebec City to the tip of Gaspe and beyond, the 

 Taconic and Acadian belts are superposed. The two belts in the Gaspe 

 Peninsula swing eastward, and even somewhat southward of east, and 

 project in that direction into the Gulf of St. Lawrence. 



Where next observable in southwestern Newfoundland, the front of the 

 Appalachian belt faces the shield, and is impressed on all older belts. It, 

 therefore, appears that from Vermont northeastward successively younger 

 orogenic belts overlap inward and front on the Canadian Shield. The 

 equivalent of the Bidge and Valley folded and thrust-faulted province 

 does not exist north of the Catskills. In Keith's terminology the Taconic 

 and Acadian orogenic systems compose a pronounced "salient" toward 

 the shield in the Vermont-St. Lawrence-Gaspe region. 



The map also shows linear Precambrian masses that were uplifted dur- 

 ing the Appalachian orogeny and, if once covered by Paleozoic strata, 

 were later subject to erosion and stripped of their mantle. The Long 

 Bange Mountains element of western Newfoundland is fairly definitelv 

 of this origin. It seems to find continuation in northern Nova Scotia, in 

 Precambrian exposures on the western side of the Bav of Fundv, and 

 perhaps even in Precambrian rocks in the Boston basin region. Pre- 

 cambrian rock forms most of the Avalon peninsula of Newfoundland 

 and also crops out in several places west of the peninsula. It has not been 

 proved that this region is one of late Paleozoic uplift, but only inferred 

 because of the numerous escarpments and shore fines that parallel the 

 known Appalachian elements of western Newfoundland, and the faults of 

 Conception Bay which resemble those of the western Carboniferous 

 basins. It ties in well with the extensive Precambrian area of eastern 



