114 GEOLOGICAL SURVEY OF THE TERRITORIES. 



The following table gives the comparative thickness of the Silurian 

 strata as noted up to the present time in Colorado : 



Locality. 



Thickness of Si- 

 lurian in feet. 



Glen Eyrie, on Camp Creek 



Near Manitou, by Mr. Win.H. Holmes 



Trout Creek, in Bergen Park 



In Park range 



On Eagle River 



North of Grand River, in Mr. Marvine's district 

 In Dr. Endlich's district, 1873 



113 



Maximum, 400 



150 to 250 



350 



820 



Maximum, 500 



40 to 80 



DEVONIAN AGE? 



Dr. Endlich discovered a series of limestones in his district, in which 

 there were characteristic Devonian fossils, and Mr. Marvine also obtained 

 Devonian fossils in his district. .While in the field I supposed the 

 Devonian to be entirely wauting, and I have no positive data by which 

 to define its limits in my district. Still there is the possibility of its 

 presence; and if so, the limestones just above those given in the section 

 of the Silurian will probably represent the formation. For the present, 

 and until more reliable data can be obtained than I now have, I will 

 include them in the section of the lower portion of the Carboniferous. 

 They have a total thickness of over 1,000 feet. It is possible that the 

 lower portion may be of Silurian age. I was unable to get a detailed 

 section of them, so that all opiuions are somewhat conjectural. 



CARBONIFEROUS AGE. 



Immediately above the limestones mentioned above, under the head 

 of Devonian, is a series of strata having a blue fossiliferous limestone at 

 the base, which is succeeded by sandstones and interlaminated shales 

 varying from fine-grained and even-textured to coarse and conglomeritic 

 layers. They are nearly all micaceous, and generally of a greenish-gray 

 color, although in the lower portion they are red and pink. Some of 

 the layers contain Carbonaceous material. From the fossils I discovered 

 in the limestone at the base of these beds, and their lithological identity 

 with the Carboniferous layers of the Park range as exposed on Four- 

 Mile Creek,* I have referred the series to the Carboniferous horizon. 

 It was impossible to define the boundary between the Carboniferous 

 layers and those above, which are probably Permian, as the latter are 

 comformable and form a continuous series, so I have arbitrarily chosen 

 a line to separate them. 



The Carboniferous formation was well developed in Mr. Marvine's dis- 

 trict, and characteristic fossils were found by him in abundance. To his 

 report the reader is therefore referred for more detailed information. 



Eagle River. — On the Eastern branch of Eagle Kiver above the canon, 

 and on the branch coming from the Blue Kiver range, the formation is 

 well developed. Unfortunately we did not have time to follow the 

 streams, where we might have discovered man}* points of interest in 

 regard to these beds. 



East of the broad meadow on the eastern branch, above its canon, 

 Mr. Holmes, in 1873, found characteristic fossils, tipirifer, Productus, 

 Grinoids, &c. 



Below the canon of the Eagle, opposite the mouth of Roche-Mou- 

 tonuee Creek, the formation is well shown in the bluffs. It, however, 

 * Section No. 18, page 231, Report U. S. Geol. Survey for lti73. 



