48 



GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



calcareous. The talus at the base of the cliffs, like that of the andesitic 

 intrusive of Stellaria Creek, is arranged in morainal ridges, with a depres- 

 sion between these heapings and the base of the cliff. The valley of 

 Fan Creek has been cut in the low anticline, exposing the Madison lime- 

 stones overlain by the Quadrant quartzites, with the softer Mesozoic rocks 

 forming higher slopes to the north. In the small drainage cutting the 

 slopes north of the creek the following section was measured: 



Fan Creel; section. 



Num- 

 ber. 



Feet. 



Dakota.. 



15 Dakota conglomerate and sandstone, the latter gray, with white spots. 



14 Sandstone, rusty yellow, blotched with pink, slightly calcareous 125 



. 13 Limestone, dark gray, crystalline 



Ellis 

 sandstone. 



Ellis I 

 limestone. | 



Teton J 

 shales. 



Teton i 

 limestone. S 

 Quadraut i 

 quartzite. J 

 Madison > 

 limestone, i 



12 Limestone, fissile and shaly, gray 



lie Arenaceous limestone, gray, crumbly, rusty 



116 Shales and crumbly limestones 



llrt Limestone, crystalline, gray, dense, splintery, argillaceous 



10 Arenaceous limestone, or calcareous sandstone, light brown-gray 



9 Limestone, grading at top into No. 10. The limestone is pure and full of 



fossils 15 



8 Limestone, argillaceous, soft, crumbly 10 



7 Argillaceous limestones, crumbly, containing fossils, and with interbedded 



layers of harder crystalline limestone 110 



6 Red shales 20 



5 Green and blue shales 30 



4 Interval (?) 



Cherty beds 125 



White sandstones, etc 300 



Limestone, crystalline, creamy, with patches of red magnesian limestone 30 



The summit of the ridge north of Fan Creek, already mentioned on 

 page 43, forms what might be termed the northern rib of the Fan and 

 is capped by Dakota beds, whose persistent nature, combined with that 

 of the intrusive sheets of andesite-porphyry, has left the ridge sharply 

 defined. The Dakota conglomerate is but 20 feet thick and is overlain by 

 buff-colored and pink sandstones similar to those mentioned in the section 

 just given. At the head of Fan Creek a depression in the mountain ridge 

 forms a pass to the headwaters of Gardiner River. The western slopes of 

 this pass are thickly covered with soil and vegetation, and no exposures 

 are seen, but to the east the beds are well exposed where the streams from 

 the snow banks of the ridge have washed the surface of the rocks bare of 



