HATDEN.J 



GEOLOGY COLORADO RANGE. 27 



has already been done tliis region presents one of the most attractive 

 fields of geological research on this continent. The relations of the 

 fresh-water lake-deposits with the Lignitic is another interesting sub- 

 ject for investigation, and will probably be settled in connection with 

 the former. So far as we have the more important problem considered 

 we find the evidence from the vegetable remains wholly in favor of the 

 Tertiary age of the coal group. The vertebrate remains, according to 

 Professor Cope, place them with the Cretaceous group, while the proof from 

 invertebrate fossils is not strong in any direction, although, perhaps, lean- 

 ing toward the Tertiary. We must admit, however, that the lower coal- 

 beds are of Cretaceous age so far as the evidence goes. For instance, 

 the Coalville and Bear Eiver beds are most probably Cretaceous, inas- 

 much as many undoubted Cretaceous types are found in strata above 

 the coal. I admitted this evidence as far back as 1869 in a paper read 

 before the American Philosophical Society. I am more convinced that 

 farther south, in New Mexico, Arizona, and Utah, there are coal-beds of 

 undoubted Cretaceous age. The main question, then, is this : Are the 

 vertebrate paleontologists^ Cope and Marsh, jtistified i7i regarding the entire 

 Lignitic group as Cretaceous from the evidence furnished by the vertebrate re- 

 mains f During the progress of the survey this subject will be discussed 

 from time to time with all the light that can be gathered from every 

 quarter. We have in the preceding pages endeavored to describe some- 

 what in detail the sedimentary reeks as exposed in the vicinity of the Big 

 Thompson Creek, and either north or south of this point they do not 

 differ materially in their general character. We may now move 

 rapidly southward along the base of the mountaifts, noting here 

 and there some peculiar features of interest which may have escaped 

 attention in former explorations. About five miles south of the 

 Big Thompson a shaft has been sunk to some depth, apparently 

 in search of coal. It is just over the quartzite No. 1, and shows 

 very clearly the relations of No. 2 to No. 1. The shales incline 

 about 15°. In some thin mud-limestones Ostrea and Inoceramus 

 were observed in great numbers, mostly in fragments. A considerable 

 quantity of silicified wood was found here also. There is here an im- 

 portant ridge which seems to be made up of a fragment of No. 1 or a 

 stratum of No. 2 — most probably the latter, It is composed of a gray mud- 

 sandstone about 15 or 20 feet thick, and in many places filled with veg- 

 etable impressions which must have been originally formed by sea-weeds. 

 They are not distinct enough to determine, but have the forms of black 

 irregular stems, and from the mass of these markings the sea- weeds must 

 have grown here with great luxuriance. It is not uncommon for a se- 

 ries of the border layers, as alternate beds of mud-sandstone orquartz- 

 ites, with shales or clays, to occur in many of the beds. These layers 

 disappear again in shales. About two miles north of the Little Thomp- 

 son we find the quartzites standing nearly vertical in a sort of frag- 

 mentary wall. This was accounted for by another of these spurs from 

 which the greater portion of the Cretaceous beds had been worn away, 

 leaving a sort of semi-quaquaversal, (section 2,) Nos. 2, 3, and 4 in- 

 clining from a convex or dome-shaped ridge or puff (?) of No. 1. This 

 is certainly a very interesting example of the connection of the quartz- 

 ites of No. 1 in what might be called an anticlinal. The trend of this 

 puff {d) is about 30° west of north. On the west side of the iMiff there is 

 an interval of half a mile, a synclinal valley extending down from the base 

 of the mountains, underlaid with Nos. 2, 3, and 4, which originally ex- 

 tended over the puff. About two miles south of Little Thompson 

 there is another of these convex ridges {d) which shows the en echelon 



