400 EEPOET maTED STATES GEOLOGICAL SUEVEY, 



164. Unexposed. 



165. Obscure exposure of gray sandstone. 



166. Eed sliales, exposed in tlie northeast slopes of narrow valley 

 tributary to Gray's Lake. 



167. Heavy ledge gray, brown-weatbered, laminated sandstone; dip 

 35° to 45°j soutbwestward. Forms a conspicuous escarpment in crest 

 of low ridge tbrougb wbicb tbe little stream breaks its way out to tbe 

 long, gentle slope descending to the level of John Gray's Lake plain. 



168. Gray, brown- weathered, si^ar-seamed sandstone, forming four or 

 five ledges, and interbedded with chocolate-colored and pale reddish 

 shales, which appear in the open, grassy slopes over a belt several 

 hundred yards across. 



169. Flat alluvial valley, traversed by a small stream that flows out 

 into the flats of John Gray's Lake, two or three miles to the northwest. 



170. Gray, thin-bedded sandstone ; dip 30° S., 60^* W. Exposed in 

 gentle slopes on the southwest side of the vaUey, and rising into the 

 undulating upland south of John Gray's Lake, in which the following 

 obscurely exposed strata ajipear. 



171. Unexposed. 



172. Gray, thin-bedded sandstone, dip southwestward. 



173. The above ledges are followed by several successively higher and 

 similar soft sandstone beds, which show obscure outcrops in the undu- 

 lating upland which occupies a breadth of about three miles, the incli- 

 nation of the strata gradually flattening to the southwestward, where 

 they sink into a shallow depression and disappear. 



Just beyond the i^oint mentioned under 173 of the above section, a 

 low and more abrupt ridge intervenes between this depression and a 

 southeast tributary of John Gray's Lake, in which obscure exposures of 

 red and light shales were observed (174), and on the summit, at an ele- 

 vation of 300 to 400 feet above the plain, dark gray sandstone and gray 

 and buft' limestone debris occur (175), the latter abounding in Ceratites. 

 The latter deposits were not seen in sitUy and their relation to the fore- 

 going soft sandstones and pale red shales, which compose the whole of 

 the upland tract to the northeast and reach up on the southwest flank 

 of the Caribou Eange, was not ascertained. The latter locality is just 

 over our south line. In the country to the southeast. Dr. Peale dis- 

 covered the same ledge in place, from which he brought in a suite of 

 its peculiar fossils, amongst which Dr. White has recognized several 

 species of Ceratites. This ridge is separated from the low hills outlying 

 the Gray's Lake ridge on the northeast, by a rather wide, estuary-like arm 

 of Gray's Lake Basin, which soon narrows and is choked with the basaltic 

 flows that form the lower divide between this and the drainage flowing 

 south. These low, outlying hills are composed of dimly ex^iosed red- 

 colored deposits, resembling the softer shales in the above-mentioned 

 ridge, and which dip apparently southwest. The interval between 

 these ridges is, however, filled with the basaltic flow, comi^letely inter- 

 rupting the continuity of the sedimentary exposures. To the southward 

 or southeastward these deposits have the appearance of dipping into 

 the low mountain ridge on the southwest side of John Gray's Lake, and 

 which at the southernmost point visited, a mile or two south of the lake, 

 was found to exhibit an interesting anticlinal fold, with the appearance 

 of the strata curving round the southeast extremity of the ridge, where, 

 as elsewhere observed, are massed heavy deposits of red beds. But 

 within our territory that portion of the ridge south of the wagon-road 

 gap presents the structure of a monoclinal ridge comi)osed of Carbonif- 

 erous dei30sits. I am strongly inclined to the belief that a belt or zone 



