336 DESCRIPTIVE GEOLOGY. 



On Chalk Creek, above Coalville : 



AncJiuraf fusiformis. 

 Gyrodes depressa. 

 Tellina f f isonema. 

 Mactra {Trigonella)? arenaria. 



And near Uptown : 



Cardium curium. 

 Inoceramus erectus. 



From the horizon of Coalville upward geologically for 4,000 feet, 

 there is a series of varying sandstones, chiefly buff and gray in color, carry- 

 ing here and there conglomerates, with a few beds of dark olive shales. On 

 the summit of the third ridge north of Coalville, which forms the north wall 

 of Grass Canon, is a heavy buff and gray sandstone, underlaid by shales 

 and clays, which carries coal, and is rich in fossils; here were found only 

 Cardium curtum, Mactra, Inoceramus, and Ostrea; but southeast of Coalville, 

 near the CarroUton mine. Prof. F. B. Meek obtained from the same horizon 

 great numbers of marine, brackish- water, and even fresh-water types. The 

 sandstone is about 300 feet thick, and contains near its top vast numbers 

 of Ostrea soleniscus. The coal-bearing beds here, therefore, may rather be 

 included in the Fox Hill group, while, as has already been seen, the more 

 eastern coal beds are generally of a higher horizon. The next ridge north, 

 also composed of buff and gray sandstones, contains large species of Inoce- 

 ramus and isome Ostrea. These sandstones are unconformably overlaid by 

 conglomerate beds of a pinkish color, containing a variety of pebbles of 

 jasper chert and quartz, with occasional rounded fragments of limestone. 

 The discrepancy of dip between them and the Tertiary beds is here only 

 10°, while, as we have seen 10 miles up Echo Canon, the Tertiary is more 

 nearly horizontal, and the discrepancy is 25°. 



Near the head of Chalk Creek, and underlying the beds of shale and 

 conglomerate, which form the high mountain northwest of the road, is a 

 belt of conformable conglomerates, chiefly made up of pebbles not larger 

 than a chestnut, containing some, however, 2 inches in diameter, which 



