206 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



Bay area, is a nonvolcanic series present. There about 2000 feet of lime- 

 stone occur. 



In Conception Bay on the east the volcanics are absent, or if deposited, 

 have been eroded away. The Belle Isle and Wabana formations, the latter 

 carrying sedimentary iron-ore beds, are chiefly sandstones and shales, 

 about 9000 feet thick. 



The thick Ordovician sections in central Newfoundland with their 

 abundant volcanics resemble the Ordovician Ammonoosuc volcanics of 

 New Hampshire more than any strata of similar age in the Maritime 

 Provinces. 



Silurian System 



Strata of Silurian age are not known in either the western or eastern 

 divisions of Newfoundland, but in the central belt various elastics are 

 fairly voluminous. In the White Bay and Notre Dame Bay areas over 

 2000 feet of Silurian sandstones and shales have been noted. In the For- 

 tune Bay area, the Rencontre formation consists of quartzite, graywacke, 

 and volcanics, about 3500 feet thick. Other sequences in the central divi- 

 sion may prove to be Silurian. 



Devonian System 



The Clam Bank series along the western shore of St. George peninsula 

 is a coarse, red conglomerate, with intercalated masses of soft, coarse 

 brown sandstone and shaly sandstone of early Devonian age. The well- 

 rounded and polished pebbles in the conglomerates are of many kinds and 

 range up to 4 inches in diameter. The beds resemble the Triassic sedi- 

 ments of the Connecticut Valley. In places they appear nearly flat, but in 

 others they are on end. They indicate a sharp uplift immediately preced- 

 ing and collateral with their deposition, and their deformation indicates a 

 following orogeny. 



In the Fortune Bay area, the Great Bay de l'Eau conglomerate is 3000 

 feet thick, and is also believed to be early Devonian. 



Early Devonian plant impressions were discovered in the La Poile Bay 

 area of southeastern Newfoundland east of Long Range in 1940 (Dorf 

 and Cooper, 1943) in the Bay du Nord series which, because of its meta- 



morphosed character, had previously been thought of as Precambrian. 

 The fossils occur in a grayish-black slate which is associated with gray- 

 wacke and conglomerate. Much of the central plateau is metamorphic 

 and igneous rock, and a belt of schistose character flanks Long Range 

 on the east. The early Devonian fossils occurring in rocks of this terrane 

 open up the possibility that much of the stratified altered rock, previously 

 called Precambrian, is Paleozoic; and that the numerous and large cross- 

 cutting plutons are Acadian in age. Recognizing the well-established 

 Acadian orogenic history in the Maritime Provinces and in New England, 

 which includes much metamorphism and plutonic activity, a number of 

 modern investigators are classifying the stratified, altered, lithologic units 

 as Paleozoic rather than Precambrian. It seems probable that much of 

 central Newfoundland will prove to be underlain by Paleozoic rocks. The 

 recent Geologic Map of North America shows most of it as Ordovician 

 strata and Devonian intrusives. Undoubtedly more Paleozoic systems will 

 be recognized in this complex in future investigations. 



Mississippian System 



Mississippian rocks are present abundantly in the St. George Bay area 

 and in the White Bay — Grand Lake lowland. They are also known at 

 Cape Rouge and Groais Island, and in part of the Notre Dame Bay area. 

 The chart of Fig. 13.3 correlates the Mississippian formations of these 

 areas. They are chiefly elastics. The St. George Bay series contains in 

 addition some evaporites, and the Notre Dame Bay area, some volcanics. 

 Up to 3500 feet of beds have been noted in these sections. 



ST GEORGES 

 SAT AREA 



WOOOT POINT SS 

 WOOOT COVE SH.LS 

 BLACK POINT LS. 

 COOROT SH , GYP 

 SNAKE BRIGHT SH. 

 CAPE ANCUILLE SS 



DEER LAKE 



UPPER GRAY 



AND 



LOWER RED 



SHALES 



WHITE BAY 



SPEAR POINT SS.SH 



CAPE ROUGE - 

 GROAIS ISLAND 



CAPE ROUGE SH., 

 SS.. SILTSTONE 



PILIER CONGL..SS 



REO INDIAN 

 LAKE 



SHALE, CONGL. AND 

 LIMESTONE 



NOTRE DAME 

 BAY 



SPRINGOALE GRP. 



REO CLASTICS, 



VOLCANICS 



Fig. 13.3. Mississippian formations of Newfoundland, after Betz, 1948. All are regarded as 

 Lower Mississippian. 



