122 GEOLOGICAL SURVEY OF THE TERRITORIES. 



have taken the upper or more massive part of the sandstones as the 

 limit of the Triassic formation, referring all above to the Jurassic. 

 This arbitrary division was also used by Mr. Marvine last year. 



As already mentioned, these red sandstones vary but little over broad 

 areas. On the Colorado River they were observed by Newberry.* In 

 Colorado, last year, we had them in the Front range, in South Park, and 

 in the Elk Mountains, and they were readily recognized by their litho- 

 logical characters. Their general massiveness was a prominent charac- 

 teristic. 



Eagle River. — Near the head of Eagle Eiver the Red Beds do not ap- 

 pear close to the river, although they are doubtless exposed between the 

 Blue River range and Eagle River. Below the Piney they outcrop in 

 the hills bordering the valley on the east. The strike here is parallel, 

 or nearly so, with the course of the river. At the head of the second 

 canon, however, the line of outcrop crosses the river almost at right 

 angles to its course, first making a spoon-like curve shown in the illus- 

 tration in Plate II. On the south side of the river it curves to the west- 

 ward, and then gradually to the north, crossing the river again at the 

 foot of the canon, as shown on the map, (A,) and extending up into Mr. 

 Marvine's district. Opposite the canon, that is, south of it, this curve 

 forms the northern side of an anticlinal fold or break, which is shown in 

 Fig. 1, Plate I, caused by the protrusion of the trachy tic mass shown in 

 the illustration. 



A section of the Red Beds, as exposed near the Eagle River, on the 

 south side, is given below. 



No. 6. — Section of Triassic on Eagle Eiver at secotid canon. 



Base. Thickness. 



Peet. 



1. Rfd sandstones, somewhat laminated , 70 



2. Purplish sandstones 15 



3. Red and brown laminated sandstones, some of the layers being seemingly 



calcareous 193 



4. Coarse white sandstone 5 



5. Red sandstones, more massive than the lower layers, although there is some 



lamination 375 



6. Pink quartzitic sandstone ) onn 



7. Red sandstones somewhat laminated $ 



8. Massive light-colored quartzitic sandstone 10 to 20 



Total thickness 978 



It will be noticed in this section that there is considerable lamination 

 in the red sandstones. Farther westward this lamination is not so 

 decided. 



Below the canon, in the hills that rise back of the low gypsiferous 

 hills, the Red Beds form the surface, covering a large area, extending 

 across to Frying Pan Creek. They form broad-topped ridges, in which 

 the general dip is toward the north, the inclination being slight. As 

 we approach the valley of the Eagle, however, it increases and we 

 have several folds, as pointed out in the chapter on Eagle River Valley. 



On station No. 8, the red sandstones dip a few degrees east of north. 

 On station No. 9, they dip North 35° West, angle 30°-35°. 



I have already spoken of the probability of there being here a 

 synclinal fold, of which the eastern half has been removed. This fold 

 is indicated in the illustration Fig. 1, Plate III, by the dotted lines. Below 

 the valley, the river flows through a canon-like valley in the axis of an 



* Ives's Colorado Exploring Expedition, Geological Report. 



