682 SCHUCHERT AND TWENHOFEL ORDOVICIC-SILURIC SECTION 



angle is maintained under the sea for 19 miles, the distance to Anticosti. 

 Eichardson and Logan estimated that in this covered interval are hidden 

 about 1,700 feet of strata between the highest deposits of Mingan and 

 the lowest of Anticosti. The latter states that "this volume probably 

 consists of the upper part of the Birdseye and Black Eiver, with the 

 Trenton, the TJtica, and the lower part of the Hudson Eiver formation, 

 what is considered the upper part of the latter being the first rock met 

 with on the north side of Anticosti" (Logan, 1863, page 221). The 

 writers will show that strata of probable early Eichmondian age are 

 immediately beneath the base of the Anticosti series, and that, as the 

 highest rocks of the Mingan Islands are probably of Black Eiver time, 

 this covered interval may have deposits ranging from the lowest Trenton 

 to the Lorraine. The thickness of 1,700 feet, if present, is not thought 

 to be excessive for these strata, as all formations here have a greater 

 thickness than are known outside of the Saint Lawrence embayment. 



The north side of Anticosti Island is far higher — in places 400 feet — 

 and more precipitous than the south shore. There also are seen the 

 oldest strata, the greater part of the north shore being composed of the 

 Eichmondian beds. The dip here is also to the south, with the beds of 

 the east and west ends of the island somewhat elevated, so that the de- 

 posits of the medial portion of the island now lie nearly horizontal in a 

 shallow trough. 



That the strata of Anticosti are the deposits of a very shallow sea — 

 that is, within the zone of wave action, known to extend in the present 

 seas to a depth of about 150 feet — is proven by the many zones of intra- 

 formational conglomerates and limestone conglomerates made up of thin 

 flat pebbles in Divisions A, B, and D, by the abundance of reef corals 

 and coral reefs in the higher beds of C and throughout D and E, by the 

 quartz sand and coral sand deposits seen only along the north shore in 

 C and D, and the more or less argillaceous limestones and interbedded 

 zones of shale or thick beds of shale. Some of the intraformational con- 

 glomerate beds consist of the churned up sea bottom, in places upending 

 the newly deposited beds for a thickness of not less than 2 feet or rolling 

 the then soft deposits into mud balls. Such are often seen in Divisions 

 A and D. 



The general stratigraphic sequence from the Quebec shore to the south 

 side of the Mingan Islands is as follows : 



Laurentian. 

 Canadic system.' 

 Beekmantown series : Feet 



Romaine dolomites, with a thicl5;ness of at least 290 





