204 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



plateau because of a fairly flat top. Actually only remnants of a high, flat 

 surface exist, and these are about 2000 feet above sea level. High valleys 

 of late mature aspect range in elevation from 1300 to 1700 feet and are 

 correlated with the highest surface in the central plateau at 1400 to 1600 

 feet. This same surface declines to about 1000 feet in the Baie d'Espoir 

 region, and 700 to 800 feet at St. Johns. A third surface in the western 

 Long Range is at 500 to 1000 feet above sea level. In the central plateau 

 this surface is believed to mark the mature upland of 500 to 1000 feet at 

 Grand Lake — White Bay basin, and the 200-foot level at Notre Dame Bay 

 and the lower Exploits basin, and the 350- to 400-foot level at St. Johns. 

 The three surfaces, or peneplains, are regarded as sloping to the east and 

 representing corresponding tilt of the island in that direction. The pene- 

 plains were developed through fluvial erosion, not marine; and as in the 

 southern and central Appalachians were eroded, it is believed, in Tertiary 

 time. Perhaps the highest Long Range peneplain formed in the late 

 Cretaceous. 



The Anguille Mountains have an upland surface much like that of Long 

 Range. The highest points are at about 1800 feet above sea level. The 

 Serpentine Range includes the Lewis Hills and Blow-me-down Moun- 

 tains south of the Bay of Islands, Arm Mountain on the north side of the 

 bay, the St. Gregory highland on the north entrance of the bay, Table 

 Mountain on the south side of Bonne Bay, and Lookout Hills on the 

 south entrance of Bonne Bay. These several relief features are parts of a 

 basic intrusive complex. Lewis Hills have a remarkably flat surface at 

 about 2300 feet above sea level, a well-preserved, mature surface at 1300 

 to 1700 feet, and a surface shown by upland valleys at 700 to over 1100 

 feet. 



STRATIGRAPHY 



Introduction 



The stratigraphy of western Newfoundland was first summarized by 

 Schuchert and Dunbar (1934). The report also reviews the stratified units 

 of the rest of the island in the light of information up to 1934. Several 

 Bulletins and Information Circulars of the Newfoundland Geological 



Survey under the direction of A. K. Snelgrove contain additional informa- 

 tion; and a few journal articles by Twenhofel (1947), Twenhofel and 

 Shrock (1937), Dorf and Cooper (1943), Kindle and Whittington (1958), 

 and others present new stratigraphic and paleontologic information. 



The island has been divided into four sections in the chart of Fig. 13.2 

 for the purpose of listing representative sequences. A fifth section is 

 added on the west for the coast of Labrador, and still a sixth for the 

 Canadian Shield. The chart attempts to summarize not only the stratified 

 sections, but also the tectonic history. It can be referred to later when the 

 structure and tectonic history of the island are discussed. The sections 

 from west to east may represent the major stratigraphic provinces, since 

 they are taken across the strike of the linear structural elements. The 

 Notre Dame Bay section in the north-central part of the island and the 

 Fortune Bay section in the south-southeastern part of the island may be 

 parts of a common central province, the details of which are not yet 

 known. 



Cambrian System 



In western Newfoundland limestones, dolomites, siltstones, and shales 

 predominate and build up a sequence 3000 to 3500 feet thick. Along the 

 west coast for a distance of 800 miles, and especially at Cows Head 

 (between Bonne Bay and St. John Bay, Fig. 12.1) a succession of lime- 

 stone conglomerates interbedded in shales and limestone, about 1000 

 feet thick represent Middle Cambrian to Middle Ordovician time ( Kindle 

 and Whittington, 1958). The conglomerates consist of small, flat chips, 

 angular to subangular boulders, and scattered large blocks up to 600 

 feet in length. The matrix is a mudstone. The fragments came from a 

 source area where calcarenites, oolites, calcilutites, and dense fine- 

 grained, varicolored porcellanous limestones, in places with shale part- 

 ings, were accumulating. The boulders have fossils of the same age as 

 the matrix. These observations lead Kindle and Whittington to con- 

 clude that the conglomerates are not thrust breccias but intraforma- 

 tional units in a flysch sequence. The source direction could not be deter- 

 mined. 



The Burin Peninsula has Cambrian beds of carbonates, shale, and 



