116 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



Under tbe head of Devonian, I referred to these Leds, and said that they occupied 

 debatable ground. A portion of the niiper limestone may have to be referred to the 

 Lower Carboniferous, while the lower layers may be of Silurian age, leaving the center 

 to represent the Devonian. Of course, without fossils to prove their age, all opinions 

 are merely conjectures. 



The section given above holds good in detail only for the locality in 

 which it was made. The beds are very irregular in their horizontal exten- 

 sion, some of them thinning-ont very rapidly. Thus, for instance, the bed 

 numbered 17 in the section above, in another place, not more than half 

 a mile distant, was only three feet in thickness, instead of seventy-one. 

 One of the illustrations in last year's (1873) report * shows this remark- 

 ably well. Not only do they thin out, but they also change in color 

 and nature, as we trace them. A bed of red sandstone will gradually 

 fade into white, while a layer that is fine-grained in one place will 

 become conglomeritic as we follow it horizontally. The space contain- 

 ing beds numbered in the section from 18 to 22, inclusive, in another 

 place is occupied by light red conglomerate sandstones, with interlam- 

 inated dark-red shales. Above the section is a thickness of about 

 1,300 feet of strata, to which I will refer when I speak of the Permian. 

 The lower portion might be referred to the Upper Carboniferous, but 

 as there was nothing to mark the end of the Carboniferous or the begin- 

 ning, I have arbitrarily separated them. 



Below the second canon of the Eagle are outcrops of gypsiferous 

 beds, to which 1 will refer under the heatl of Permian. !None of the 

 limestones or sandstones, referred to above, outcrop until we reach the 

 Grand below the mouth of the Eagle. 



Grand River. — The rocks forming the entrance to the canon of the 

 Grand, River, that extends from a short distance below Eagle River to 

 the mouth of Roaring Fork, are limestones, probably of Lower Carbonif- 

 erous age. They also form a small caiion on the creek that joins the 

 Grand at this i)oint. Above, the valley of the creek widens, and suc- 

 ceeding the limestones are sandstones forming bluffs, especially on the 

 eastern side. Farther up the creek the gypsiferous series forms the 

 top of the bluffs. 



The following section was made about a mile and a half above the 

 mouth of the creek : 



No. 3. — Section on 'branch of Grand River. 



Base. ' Thickness. 



Ft. In. 



1. Occasional outcrops of coarse gray sandstones, with interlaminated 



greenish shales. The space in which they occur extends from the 

 ■ base of the bluff 150 



2. Fine black shales, breaking into very fine laniiuse 36 



3. Coarse conglomeritic white sandstone, in beds of from three to five feet 



thickness, with interlaminated soft greenish shales, in bands from 



two to three feet thickness 41 



4. Very hard, compact, dark, greenish-gray sandstone 32 9 



5. Coarse white conglomeritic sandstone , 16 4 



6. Hard gray sandstone, in bands of about a foot thickness each, with in- 



terlaminated greenish shales 49 1 



7. Bluish calcareous sandstone, with their bands of shaly limestone ... 45 



8. Coarse gray conglomeritic sandstone 2 



9. Massive yellow sandstones, with bands of fine black shales. These 



beds are gypsiferous at the base. They form at the point where 



the section the top of the blufi". Thickness about 200 or 300 feet. 



Total thickness 579-679 feet. 



*Fig. 15; opposite page 71, Report United States Geological Survey, 1873, 



