254 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



black colors, often weathering to a dull olive-green, very fine grained but including harder bands, 

 and generally more or less calcareous. They are throughout characterized by numerous and 

 often intricate contortions and these, with a strongly developed slaty cleavage, make any 

 attempt to determine their thickness or relations well-nigh hopeless. Neither on the lake nor 

 on the Madawaska have they been found to contain any fossils, these having probably been 

 obliterated by molecular movements;, but the occurrence of fossils at many different points in 

 the resembling strata which spread so widely to the east and south, and all of which indicate a 

 Silurian horizon, seems to justify the position first assigned them as also Silurian, and as the 

 equivalent of the upper part of the Gaspe series. 



Southwestward from Temiscouata Lake the gray to olive-green slates called 



by Bailey Lower Helderberg occupy the basin of St. John River in northwestern 



Maine. Their relations to the overlying Devonian in Aroostook have been described 



'by Bailey ^^"^ and more recently by Williams and Gregory.®" (See Chapter VI, 



L 19, pp. 325, 328.) ' 



Northeastward from Temiscouata Lake to the Metapedia section, the outline 

 of the Silurian beds in relation to the Cambrian on the north has been retraced by 

 Bailey and Mclnness.^^"' Beyond the Metapedia EUs^"* and Low®** determined 

 their distribution between the Cambrian and the Devonian as far east as the Cas- 

 capedia, whereas from the headwaters of the Magdalen to Cape Rosier the lines are 

 placed as worked out by Logan ®"^ and EUs.^"^ The areal geology of the peninsula 

 south to the Bay of Chaleur is according to the same authorities. 



The strata thus mapped as Silurian are those assigned to that period according 

 to the past and current usage of the Canadian Survey, and they include the strata 

 identified by Bailey as Lower Helderberg, which is now classed as Devonian, accord- 

 ing to Schuchert '" and Clarke. ^^^ The literature contains a number of doubtful refer- 

 ences to Silurian or Devonian, the uncertainty being due to the transitional character 

 of the fauna, which has commonly been assigned to the uppermost Silurian but con- 

 tains Devonian forerunners. EUs^"** cites observations of unconformity between 

 Silurian and Devonian on the tributaries of the Cascapedia, and Bailey *''° infers an 

 unconformity between the rocks identified by him as Niagara and Lower Helderberg 

 on Lake Temiscouata, which might be at the same horizon. The overlap of the 

 latter formation beyond the former seems to be well established. The base of the 

 Niagara, as thus identified by Bailey, is a white sandstone associated with bodies of 

 calcareous conglomerate, consisting of limestone pebbles and angular fragments in a 

 sandy matrix. No fossils have yet been found in the limestone pebbles, but the 

 position of the strata at the base of the rocks identified as Niagara and their relation 

 to the near-by Cambrian rocks are such as to suggest their derivation from the Cam- 

 brian. A marked unconformity is thus indicated. Logan***" describes two uncon- 

 formable contacts seen on the coast near the line between Gaspe and Bonaventure 

 counties, as follows: 



The vertical strata of this group [the "Quebec group"] extend along the' coast toward Anse 

 a la VieiUe, where they are overlain by the inclined strata of the Gaspe limestones, which in their 

 turn support the Bonaventure conglomerates, the three series being unconformable with each 

 other.- 



The proofs of this double discordance lie within a space of half a mile, a little less than 2 

 miles westward of the line between the counties of Gaspe and Bonaventure ; and as there is no 

 concealment of strata, the whole is readily apparent to the eye. The smoothly worn edges of 



