206 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



Following this description Logan gives a section on the international boundary 

 showing two synclines, modified by thrust faults. 



The equivalents of the above-described strata near Phillipsburg when traced 

 south into Vermont are known as the Fort Cassin beds, according to Whitfield. °^ 

 (See K-L 18, pp. 126-127.) Their extension northeastward along the northwest 

 side of the Sutton Mountain anticline is minutely discussed by EUs.^"' The fossils 

 which have been collected at various times for the Canadian Survey from these 

 rocks are reported by Ami"" under the heading "Phillipsburg series." 



Southeast of Sutton Mountain Ordovician strata again occupy a large part of 

 the section at least as far east as the international boundary. Their extent eastward 

 in Maine is obscured by their resemblance to the soft slates of the Silurian, by the 

 featureless drift and forest covered character of the country, and by intrusions of 

 igneous rocks. (See Chapter VII, p. 350.) The strata identified in Canada are 

 known as the Magog shales and classed as probably of Trenton and Utica age. 

 Ulrich believes the Magog to be pre-Utica. They contain graptolites which are 

 described as follows by Lapworth.^^^ (See also a paper by Gurley.^*^) 



Matrix, soft, thin-bedded and flaking silvery shales, greenish gray in color (originally black), 

 apparently altered and spotted by contact metamorphism. 



1. Dicranograptus ramosus Hall. 



2. Diplograptus angustifolius Hall. 



3. Diplograptus foliaceus Mjirchison (=pristia, Hall). 



4. Diplograptus perexcavatus Lapworth. 



5. Climacograptus bicomis Hall. 



6. Climacograptus coelatus Lapworth. 



The fossils are all in a most miserable state of preservation, but all the forms named above 

 are easily recognizable. These fix the age of the strata as Utica or Marsouin. or Normans Kill, 

 but somewhat higher in the series than the typical Normans Kill beds. They may safely be 

 termed Upper Llandeilo or Lower Bala and placed generally above or about the horizon of the 

 Trenton or Utica rocks of the western area. 



The Quebec formation," distinguished by Ami,^^^ consists of dark bituminous 

 shales with hard calcareous bands, limestones, and conglomerates, several hundred 

 feet thick. The conglomerate forms Citadel HiU and has been described by 

 Weston, *^^ who quotes Ami as follows: 



Alongside and up Mountain Street a bold cliff of conglomerate occurs, containing large 

 bowlders, embedded in a shaly and calcareo-argUlaceous paste with an admixture of quartz- 

 grains. 



According to Ami^^'" and Ford^^^ the fauna by which the Quebec formation is 

 characterized comprises Black River and Trenton types and possibly upper Chazy 

 forms. 



Not only in the vicinity of Quebec, but thence along the lower St. Lawrence 

 (Island of Orleans, St. Joseph de Levis, St. Simon, Riviere de Loup, Bic, etc.) 

 there occur Ordovician shales, presumably of several horizons, which locally include 

 fragments, bowlders, or pebbles of fossiliferous limestones of earlier Ordovician 

 and Cambrian formations. 



Logan ^**' describes the rocks in his account of tne '' Quebec group. " Many of 

 the occurrences probably represent rather the equivalents of the Sillery and Levis 

 than those of the Quebec formation, as restricted by Ami. 



" See table of formations about Quebec, quoted on pp. 202-203. 



