34 DESGEIPTIYB GEOLOGY. 



The following sections, the one taken at the northern end of the map, 

 near the Chugwater, and the other 55 miles to the southward, near where 

 Box Elder Creek leaves the mountains, agree very closely in general out- 

 line, and serve to show the character of the Triassic rocks. 



At the Chugwater, we have : 



1. Eeddish-yellow sandstone. 



2. Bluish-white cherty limestone, 6 to 10 feet. 



3. Fine red sandstone. 



4. Compact arenaceous limestone, 3 or 4 feet. 



5. Eed shales. 



6. Fine red sandstone, with interstratifled beds of clay. 



7. Heavy massive red beds, with layers of fine conglomerate. 

 The entire section showing between 500 and 600 feet of strata. 



At Box Elder Creek, we have: 



1. Reddish-yellow sandstone "^ 



2. Fine-grained earthy sandstone, with layers of gypsum I 



3. Thin bed of blue limestone j 



4. Laminated shales, with some red clays j 



5. Yellowish-red sandstone 100 feet. 



6. Massive red sandstone 300 feet. 



7. Coarse red sandstone, with conglomerate 100 feet. 



650 feet. 

 It is evident, from the foregoing- sections, that sandstones form by far 

 the greater part of the entire series of strata. Even the conglomerates, 

 shales, clays, and earthy beds, which occur interstratifled throughout the 

 formation, appear more or less arenaceous, and are really closely allied 

 to true sandstones, only showing considerable diversity in texture and 

 mechanical conditions. The conglomerates would appear to be much more 

 prevalent near the base of the series, especially south of the Cache la 

 Poudre, where they lie resting directly upon the Archaean body, and carry 

 considerable detrital material, derived from the lower rocks. Shales and 

 impure clays, which, in thin layers, may be found anywhere from the base 

 to the summit, characterize the middle formations; while the upper beds 

 are usually finer-grained, with an earthy appearance, and carry thin beds 

 of limestone and gypsum. 



