pi:.4LE.] GEOLOGY CEETACEOUS NO. 2 AND NO. 3. 135 



Pecopteris confirms the inference derived from other sources, tbat the 

 lignite bed containing it lies just at the point of juuction between the 

 Cretaceous and older rocks, and showing a mingling of forms belonging 

 to the two formations, proving the impossibility of drawiug sharply the 

 lines of division." 



In the bluffs, at the mouth of the Gunnison, below the lignitic beds, 

 I found a specimen of ScapJiite, which marks the layer of Cretaceous 

 age. It probably represents the equivalent of layer No. 13 in the second 

 section given above by Newberry. If so, the identity of the sections 

 with mine would seem to be pretty clearly indicated. 



MIDDLE CRETACEOUS. 



As I have already indicated, it is impossible in our district to give the 

 exact limits of the different formations comprehended under No. 2toNo. 4, 

 inclusive. As the shaly character prevails throughout the series, I have 

 included them all under the same head. At the base in No. 2 they are 

 decidedly arenaceous, the beds just above the Dakota group being 

 laminated sandstones. Gradually they become more and more argilla- 

 ceous, and near the top thin bands of limestone appear. 



Cretaceous No. 2 and Wo. 3. 



Exposures of the Fort Benton group and the Niobrara division are 

 seen in the valleys of the Grand and Gunnison Rivers, and on the North 

 Fork of the Gunnison. Want of time precluded the possibility of mak- 

 ing a complete section from the base of the series to the top, although 

 I succeeded in getting several sections which will give the general 

 characters of the strata. The layers of No. 2 were not generally so well 

 exposed as those of No 3. The higher we go in No. 2, as exposed in our 

 district, the more shaly and argillaceous do the beds become, and in 

 No. 3 they are also calcareous. 



Eagle River. — On the north side of Eagle River, opposite the second 

 caiion, as viewed from the semicircular ridge of stations 6 and 7, the 

 Fort Benton group and succeeding divisions of the Cretaceous are seen 

 outcrojjpiug in the most beautiful manner, as shown in Plate II (be- 

 tween b and c). On the south side all have been removed excei^t a few 

 remnants of No. 2, and perhaps also of No. 3 in places, leaving the sand- 

 stones of the Dakota group as the floor of the semiquaquaversal already 

 described. Still farther south, in the circular area of Cretaceous near 

 the Eagle (see map A), remnants of No. 2 and No. 3 are seen, as shown 

 in the section in Fig. 1, Plate I. 



Grand River. — In the range of hog-backs, extending from the Elk 

 Mountains along Roaring Fork and Grand River, and finally crossing the 

 latter, there are exposures of all the Cretaceous strata above the Da- 

 kota group. There was no opportunity here to make any sections. 



On the south side of Grand River, in low bluhs above the mouth of 

 the Gunnison beds of No. 2 and No. 3, outcrop, black shales prevailing. 



Gunnison River. — Under the rhyolitic and breccia-covered areas, bor- 

 dering the Gunnison above the Grand Canon, there are in all proba- 

 bility fragments of formations No. 2 and No. 3. They are exposed be- 

 neath the mesas that stand between Slate or East River and Ohio Creek. 

 The exposures of the beds immediately above No. 1, between the North 

 Fork of ti;e Gunnison and Rock Creek, will be referred to bj Mr. 

 Holmes, in his report on the geology of the Elk Mountains. 



Between Smith's Fork and the North Fork of the Gunnison there is^ 



