574 A. W. GRABATJ TYPES OF SEDIMENTARY OVERLAP 



taken into consideration, since we can never be absolutely certain of the 

 accuracy of the sections made in such regions. The general correspond- 

 ence of the facts to the requirements of the theory seem, however, to sug- 

 gest that the correlations as here given are correct. 



In comparing the Myra valley section with the Lower Cambric strata 

 of eastern Newfoundland (811 feet at Trinity bay, 80 to 100 feet at 

 Manuels brook, or even the greater thickness of 1,200 feet at Hanford 

 brook), the discrepancies are such as can not readily be accounted for by 

 differential rate of deposition. In respect to the Trinity and Conception 

 Bay sections, it has already been shown that the difference is in part 

 accounted for by progressive overlap, and the progressive disappearance 

 of the lower members. But this is not altogether the case, since there is 

 a difference of nearly 300 feet in the beds above the Smith Point lime- 

 stone. This, however, is accounted for in the Manuels Brook section by 

 an erosion interval, as shown by the conglomerate at the base of the next 

 succeeding Middle Cambric, the pebbles of this conglomerate being de- 

 rived from the underlying Etcheminian. In the Smith Sound (Trinity 

 Bay) section, however, deposition appears to have been continuous from 

 lower to middle Cambric time, since no erosion interval is recorded. 

 Walcott, moreover, correlates the basal 130 feet of the Middle Cambric 

 of this section with the Protolenus beds of New Brunswick. If this 

 correlation is correct, the eastern Newfoundland section represents only 

 the upper part of the New Brunswicktown (Hanford Brook) section. 

 The same reasoning would lead us to regard both the eastern Newfound- 

 land and New Brunswick sections as representing only the upper part of 

 the sections shown in eastern Cape Breton. This conclusion is, of course, 

 based on the supposition that no very pronounced unrepresented interval 

 occurs at the top of the Etcheminian in either the eastern Newfoundland 

 or the New Brunswick section. 



Northern Appalachian area. — In eastern Labrador and western New- 

 foundland Lower Cambric strata rest with basal conglomerates and sand- 

 stones (often arkoses) upon the gneisses and other pre-Cambric rocks. 

 They pass upward into shales and limestones, of which over 1,700 feet 

 are exposed at Bourne bay, Newfoundland. The fauna of these beds is 

 the typical Olenellus fauna of the Appalachian province. Upward these 

 strata are succeeded by nearly 1,500 feet of limestones, with some shales 

 and a quartzite near the base, all of unknown age, while above there is 

 400 feet of limestone carrying a lower Ordovicic fauna. At Canada bay, 

 Newfoundland, 2,500 feet of conglomerates, shales, and igneous rock 

 form the base of the Cambric series and are succeeded by nearly 3,000 



