34 GEOLOGICAL SURVEY OF THE TERRITORIES. 



miles northeast of Platteville, two industrious miners have sunk shafts 

 in two places. The first one passes through the following beds, from 

 the surface: — 



1. Yellow sand-clay 42 feet. 



2. Clay or soapstone, with 3 inches of a black material and called by the min- 



ers smut 2 feet. 



3. Clay 4 feet. 



4. Ahedofshells 3£ feet. 



5. Clay 6 inches. 



6. Darksaud.... 1£ feet. 



7. Sandstone, yellow and gray 10 feet. 



8. Clay., : 4 feet. 



9. Coal 2\ feet. 



10. Clay-shale _ « 4 inches. 



11. Fice saudyclay .' : 2 feet. 



12. Coal. 



Forty- eight feet from the surface, the workmen came to a remarkable 

 bed of shells. Masses were thrown out upon the surface 18 inches in 

 thickness, a mere aggregate of shells. Anomia, and the same species 

 of cyrenoid or brackish- water shells, found over a workable bed of coal 

 at Hallville, on the Union Pacific Railroad, have been identified. About 

 300 yards from the last shaft, a second one was sunk 52 feet, passing 

 through a bed of coal 29 inches thick, which is being wrought with great 

 industry and some profit. These mines are just on the east border of the 

 South Platte, while on the west side the Upper Cretaceous beds are exposed. 

 Thin remnants of the Lignitic strata may occur on the west side, but no 

 trace of coal in that immediate vicinity. We may, therefore, reason- 

 ably infer that this thin bed of coal near Platteville lies very near the 

 base of the Lignitic series. 



The next locality which we may mention is still farther to the north- 

 ward, about ten miles to the northeast of Greeley, called Higley's mine, 

 on section 20, township 6, range 66. The mine is opened in the level 

 prairie, thirty miles east of the base of the mountains. The shaft passes 

 through horizontal layers as follows : — 



1. Arenaceous clay. 



2. Hard bluish quartzitic sandstone 2 feet. 



3. Clay -. 4-Heet. 



4. Coal 2^ feet. 



5. Floor of sandstone. 



A few fragments of leaves were observed in the hard sandstone, but 

 no other fossils. Shafts have been sunk in many other places east of 

 Greeley, but only thin beds of rather poor coal were detected. It is not 

 probable that any valuable beds of coal will ever be discovered in the 

 immediate vicinity. 



Our examinations of the country between the South Platte and the 

 base of the mountains, especially along the valley of the Cache a la 

 Poudre, were productive of most important results. We found in an 

 extensive series of sandstones, sands, clays, etc., a great variety of marine 

 invertebrate fossils belonging to well-known Cretaceous types. The 

 rocks are all quite peculiar, indicating by their structure that these dep- 

 ositions took place in moving waters. A few of the shells were found 

 in the clays, and many of them were inclosed in dark, round, calcareous 

 concretions, scattered through the clay; but most of them occur in 

 isolated groups on the under or upper surface of a layer of sandstone, as 

 if they had been swept into eddies or shallow depressions. As we have 

 often stated, the physical history of these massive formations is written 

 on the rocks themselves. 



