PEALE.J GEOLOGY DAKOTA GROUP EAGLE EIVER. 129 



Dakota group. In tlie same series I also found, near Glen Eyrie, a few 

 miles from Colorado City, specimens of a liugula too indistinct for spe- 

 cific identification. In the Elk Mountains numerous impressions of 

 dicotyledonous leaves were noticed, most of them fragmentary and in- 

 distinct. 



On the Gunnison Eiver during the past season (1874) I found a frag- 

 ment of a sassafras-leaf like S. inirabile, near station 60, and in the 

 bluffs near the mouth of the Gunnison I obtained a Cretaceous Scaphite. 

 In various parts of the Elk Mountains Mr. Holmes found impressions 

 of a Salix. 



Professor Xewberry* recognized the group in ISTew Mexico. I shall 

 hereafter refer ta the identity of his sections with those made by me 

 on the Gunnison. 



Speaking of the rocks as exposed in New Mexico, he says : " The 

 paleontological evidence of the age of these rocks is quite conclusive 

 and of unusual value, as it fixes the place in the geological scale, of a 

 well-marked formation in New Mexico, and one which has been the sub- 

 ject of considerable discussion. In the second member of the Cretace- 

 ous portion of the section, counting from the base upward, are con- 

 tained fossils which are characteristic of the Cretaceous formation in 

 Texas and Nebraska. These are Inoceramus crispii and Gryphwa pitcheri, 

 well known Cretaceous fossils, common in Texas and the Indian Terri- 

 tory, and, in greater numbers, specimens of an ammonite {A.pericarina- 

 tiis), highly characteristic of Nos. 1 and 2 of Meek and Hayden's section 

 of the Cretaceous rocks on the Upper Missouri. There is no doubt of 

 the parallelism of the group of sandstones with those of the base of 

 Meek and Hayden's Cretaceous section." 



The lithological characters will be shown in the various sections 

 given, as I consider the formation according to its geographical distri- 

 bution in our district. 



Eagle River. — Until we reach the head of the second caiion there are 

 no outcrops of Cretaceous age on the south side of Eagle River. Here, 

 however, the sandstones of the Dakota group cross from the north and 

 form a semicircular ridge, crossing to the north side again at the lower 

 end of the canon. In Plate II the group on the north side at the head 

 of the canon is shown at a a. 



The semicircular line of outcrop is shown on map A. Stations 6 and 

 7 were located on its edge. The dip of the strata on station 6 was North 

 cP East, and on station 7 North 85° East, the angle of inclination about 

 20'^. In this basin, included between the ridge and the river, the overlying 

 strata have almost entirely been removed, the upper part of the group 

 forming the greater part of the floor of the depression or semiquaqua- 

 versal. A section through the center of this basin is shown in Fig. 1, 

 Plate I, from the point a to the Eagle River. I was unable to get a 

 section here, so that I cannot say how thick it is. On station 6 the 

 rock is a coarse white siliceous sandstone. Where it is in contact with 

 the volcanic rock, as seen in the section and on the map, it is meta- 

 morphosed. 



Below station No. 7 there is the following section, from below up : 



1. Gray sandstone, greenish coating on the surfaces of the laminae. 



2. Hard greenish mottled limestone. 



3. Greenish gray sandstone. 



4. Blue limestone. 



5. Sandstones forming the station. 



* Ives's Colorado Exploring Expedition, Geological Report, page 85. 

 9 H 



