Section IV, 1887. [ 2S ] Trans. Eoy. Soc. Canada. 



II, — The Faults and Foldings of the Pictou Coal Field. 



By Edwin G-ilpin, Jun., A.M., F.G.S., Deputy Commissiouer aucl Chief Inspector of Mines. 



(Read May 25, 1887.) 



This coal field is comparatively limited in extent, being eight miles long and three 

 and a half miles wide, and presents the shape of a pear wtih its stem pointing to the 

 east.^ In it, however, are exhibited on an unusual scale three of the great features 

 of geology : a development of large seams of coal, a system of immense faults, and an equal 

 measure of denudation. 



The first is shown by the presence of a number of seams exceeding ten feet in 

 thickness — one, the Albion Main seam, being thirty-nine feet thick. The faults 

 equal in magnitude the thickness of the sediments of the district, which the late Sir 

 William Logan estimated at b,b&l feet. The denudation has been on an equally exten- 

 sive scale. 



The district having its greatest length in an east and west direction, is bisected by 

 the East Eiver. In the western division, the lower half of the productive measures out- 

 crop, and extending across the river into the eastern division, are there covered by the 

 upper group. The general arrangement of the measures is that of a main east and west 

 synclinal, modified by transverse foldings at each end, giving rise to subordinate but 

 almost independent basins. There is also a subordinate synclinal lying south of the main 

 fold ; and in the succeeding millstone grit, two more synclinals have been noticed. 



However vain conjecture may b? as to the former extent of this coal field, enough 

 can be deduced from its present position and extent to warrant the presumption that it is 

 now but a fragment. Taking the western division, the strata are folded in a synclinal 

 two miles wide, the northern edge dipping at an angle of about eighteen degrees, and the 

 lower beds turn over into the subordinate synclinal referred to above. This section, 

 recalling in its regularity the typical examples given in geological text-books, undoubtedly 

 extended at one time to the full limit of the minor synclinal. Taking in a similar manner 

 the eastern division with a total thickness of 5,000 feet, there would be presented, on a 

 reduction to sea level, a mass towering high above any mountain of the Lower Provinces, 

 and as nature never formed coal fields as this one is now presented between bounding 

 faults, like layers in a chest, it is evident that formerly the coal field must have had 

 greatly enlarged limits. These remarks, referring more particularly to the southward 

 extension of the coal field, are equally applicable to its northern outcrop. 



Immediately to the north of the coal field with its upturned edge, comes an immense 

 mass of conglomerate, referred by the ofiicers of the Geological Survey to the top of the 



Eeference may be made to the map of the Pictou Coal Field. Geo. Sur. Rep. 1869. 



Sec. iv,11887. 4. 



