368 GEOLOGICAL SUEVEY OF THE TEERITOEIES. 



letter of Prof. E. T. Cos, who, in company with Dr. E. Owen, found 

 specimens of Scapkites and Inocerami in strata supposed to belong to 

 the Cretaceous Lignitic, as quoted by Dr. Leconte in his Notes ou the 

 Geology of the Union Pacific Eailway, (p. 19.) Professor Cox says, con- 

 cerning these specimens, which are still in his cabinet — 



I copy from my memorandum -book the section and notes made at Spanish Peak, a 

 range of the Eocky Mountains, from a siage-station on Purgatory Creek. 



Cretaxieoiis. 



Hard band 20 feet. 



Thin and thick bedded sandstone, ) 



Schistose sandstone and shale, > 200 feet. 



Solid bedded sandstone. ) 



Thin coal 



Solid grit, with pebbles , 70 feet. 



Talus at base - -• 400 feet. 



The talus rested upon the table-land, which ia 240 feet above the bed of the creek ; 

 total height, from bed of creek to top of section, 930 feet. The ridge extended back 

 from face of hill, and appeared to be about 100 to 150 feet higher. — (Note on section 

 from memorandum-book :) Found in the wash at foot of talus in the above section, 

 Scaphites iwdosa, and a species of Inoceramus. 



The section is similar to those given in Hayden's Eeport for 1872, (p. 

 319), of the Lignitic and its underlying heavy sandstone, on the Purgatory 

 Creek, near Trinidad, which is underlaid by a talus of Cretaceous black 

 shale, No. 4. It compares especially well to my own, in the same report (p. 

 320), of the range opposite Trinidad, where the underlying black and 

 Cretaceous shales and covered space to the bed of the creek measure 300 

 feet. From this place, and along the stage-road to Spanish Peak, the 

 distribution of the strata is the same, the heavy Lignitic sandstone tow- 

 ering over the talus of the black shale, like a wall, as reported, {loc. cit., 

 p. 321,) and overlaid by the beds of lignites, or the productive Lignitic. 

 That, therefore, the Cretaceous fossils found at the base of the talus of 

 black shale No. 4 do not prove that the Lignitic above is of Cretace- 

 ous age is evident enough. The section of Professor Cox, on the con- 

 trary, confirms the deductions taken in relation to the superposition of 

 the Tertiary Lignitic to the Cretaceous in that part of the country. 



The authority of Captain Berthoud, of Golden, has been often quoted 

 on the same subject, and is generally considered as of great weight in 

 geological matters of Colorado, a region which this gentleman has for 

 many years surveyed for the construction of railroads and carefully 

 examin€d with the eye of a practical geologist. He has been reported 

 as supporting the assertion that Cretaceous mollusks had been found 

 above the beds of* the Lignitic formations. In regard to my inqui- 

 ries on this subject, he had, like Professor Cox, the kindness to give his 

 detailed opinion in a letter, whose statements are worth preserving. He 

 says, 



1st. That if Professor Stevenson observed iTiocerami, Ammonites, ScapTiites, Baculites, 

 NuculcB, &c., in superposition to Lignitic strata of Colorado, it is clear to me that it is 

 only a case of local inversion ; i. e., that, as shown in our basin of Golden, the Lignitic 

 sandstone has been so tilted up that, with the coal-seams near by, it was thrown over 

 the perpendicular, and thus Cretaceous strata would appear in superposition. 



2d. That between this Lignitic and the Cretaceous beds holding Inoceramus, &c., 

 on Bear Creek, there is fully one mile on an e^st or west line, so that the Cretaceous 

 beds and the Lignitic coal-shale, fire-clay, and sandstone are not conformable in dip, 

 and clearly show the superposition of the Lignitic beds. This is undoubted, as the 

 Cretaceous limestone debris, under green and yellow clay-beds, disappear under the coal- 

 beds at our old camp on Bear Creek that you visited with me. 



At Golden I cannot see that the Cretaceous beds are conformable to the sandstone 

 and coal ; so far I wrote to A. E. Marvine. Now, I will add to this for you some other 

 remarks. It has always seemed to me a stumbling-block when ten years ago, or more, 

 and until 186S-'69, 1 supposed and believed that our coal was Cretaceous, to find every- 

 where, when examined by me, that there was no conformability between the Lignitic 

 Measures and the outcrop west ; and that at Ealston, Bear Creek, Table Mountain, the 



