BITUMEN, ASPHAL TUM, PETE OLEUM, ETC. 213 



Those of the corniferous are still more bituminous. Many fossils, 

 chiefly of the genus Heliophyllum, are surrounded and their cells filled with 

 bitumen. In some localities the bitumen is solid and assumes the form of 

 asphaltum or mineral pitch. 



According to Prof. James Hall, mineral oil is found in the septaria of 

 the higher Devonian beds and also in the underlying sandstone of the Port- 

 age and Chemung group. The oil wells of Pennsylvania and Ohio are ex- 

 tended into the sandstones, but it is even probable that the oil may origi- 

 nate in the Cornifierous below. Prof JSTewberiy thinks the oil of Ohio and 

 Kentucky is derived from Huron shales (Portage) at top of the Devonian, and 

 that some of the Pennsylvania oil wells derive their supply from the same 

 horizon. The wells of Western Canada, according to the Canadian geolo- 

 gists, issue from the Corniferous formation. At Enniskillen the borings ex- 

 tend 200 to 300 feet in the overlying Chemung and Hamilton shales, which 

 have also 40 to 60 feet of claj^ and gravel upon them. The surrounding 

 country hero is generally level, and near Petrolia the overljnng clay has a 

 nearly uniform depth of 100 feet, beneath which the borings penetrate an 

 average thickness of 380 feet of interstratified blue clay, dolomite, shales 

 and marls of Hamilton and Chemung to the oil producing stratum. The 

 theory is that the oil originates in limestones and is retained in a reservoir 

 formed of the overlying sandstone.-'^ 



The petroleum of Athabasca and the northwest territory of British 

 America occurs in Devonian shales and in large quantities. 



On Oil creek. Pa,, the chief oil producing rock is a third sandrock below 

 the surface, and an oil producing spot in the Pennsylvania regions is an 

 area overlying, from 500 to 1,500 feet, a bed of porous conglomerate from 3 

 to 75 feet in thickness, the thickest portion of the rock giving the best well, 

 and the thickness is generally found in the center of the area, the rock taper- 

 ing to the edges. The rock is considered the third sandrock, but we learn 

 that it is not always continuous, but that there do exist detached beds of lens- 

 shaped masses of third sandrock. This sandstone has been passed through 

 at its greatest known depth, at 1,976, feet, and appears to be a white pebble 

 conglomerate containing some green oil. In the same well (Jonathan "Wat- 

 son's) the next highest sandrock was at 1,507 feet, and was considered the 

 true third sandrock. f 



Prof. Lesley says that the Pennsylvania oils are not entirely confined to 

 throe oil sands, but extend through at least 3,000 feet of measures. 



There are three chief oil sandrocks, all below the carboniferous strata. 

 Some of the flowing wells have been penetrated to these lower sandrocks, and 

 Prof Lesley also says that the Canada oil bearing rocks pass under Lake 

 Erie and are far below the Pennsylvania oil sands of the Allegheny river 

 country. j: 



The surface rocks of the oil wells of West Virginia are sunk in Carbonif- 

 erous strata, but some of the oil is probably from below. 



■■■•' Canada Geological Eeport, 1863. t Penn. Geol. Eep , J., 1874. X lb. 



