PAPERS OX GEOLOGY AND GEOGRAPHY 401 



derhook is largely eroded and the declivities of the erod- 

 ed surfaces are apparently abnipt and shai*p since a hori- 

 zontal distance of a few hundred feet may make differ- 

 ences of 60 or more feet in the thickness of the shale or 

 may even account for its entire disappearance. 



The lower phase, the Fern Glen limestone, averages 

 about 30 feet in thickness, but with extremes as low as 

 11 and as high as 60 feet. The limestone is coarse 

 grained and of variegated shades of brown-red, dull red- 

 purple, pink, green, and white. The red and pui-ple 

 limestones have a dull, dead lustre, while the remaining 

 pink, green, and white have the vitreons lustre of crys- 

 talline calcite. The red color of the limestone is prob- 

 ably due to minute particles of red ferruginous shale and 

 hematite. Locally the Fern Glen contains chert, crystal- 

 line calcite, and commonly the top or medial portions 

 contain thin beds of red, gray, or greenish-gray shale. 

 Where the formation is thick, however, it is roughly 

 divisible into the upper and lower red limestone beds, 

 with intennediate beds of gray or green shale. 



In the vicinity of the anticline, the drillers estimate 

 the interval between the top of the Feni Glen and the 

 top of the Kim ms wick as 200 feet. As a nile this ap- 

 plies to the interval between the top of the "red rock" 

 and the first showing of oil below the ''black shale". 

 Logs bear this out, and in ahnost every case the interval 

 between the two horizons mentioned is from 200 to 220 

 feet. This is rather sui"prising when it is remembered 

 that the Devonian in this area is unconfonnable above 

 and below, and varies from a few feet up to 75 feet in 

 thickness, and that the Trenton cap, the Femvale, also 

 is not of constant thickness. 



THE DEVONIAN SYSTEM 



Judging from the number of logs which do not re- 

 cord the Devonian limestone, it is not every where pres- 

 ent. Whether it has been logged with the Fern Glen or 

 really is absent can not be stated definitely. However, 

 in the 20 logs in which it is recorded, it has a range 

 in thickness of from 20 to 75 feet and averages 40 feet. 



