264 W. Cross — Denver Tertiary Formation. 



unconformable with all earlier deposits. What the extent of 

 the Denver beds may be in this direction is now unknown, but 

 it is probably not great, for the larger part of the Formation 

 was destroyed prior to the deposition of the Monument 

 Creek. 



The important exposures. — The only strata belonging to the 

 Denver beds which are particularly mentioned by earlier 

 investigators are in Table Mountain, at Golden, and while these 

 are truly typical of the Formation their stratigraphical rela- 

 tions are there certainly obscure. In the course of the present 

 work hundreds of out-crops were studied, scattered over the 

 entire area, in the banks of streams, of ditches, and in numer- 

 ous railroad cuttings. The outcrops of the plains must, how- 

 ever, be interpreted in the light of the more extensive expos- 

 ures of Table and Green Mountains. In South Table Moun- 

 tain the lower third of the series is best shown, while one must 

 go to the neighboring Green Mountain for all the higher strata 

 and for a clear exhibition of the stratigraphical relations of the 

 whole. 



Green Mountain lies upon the western border of the plains, 

 midway between Golden and Morrison (see map), and is so 

 related to the great fold that the strata at its western base are 

 in vertical position while those of the summit are horizontal, 

 and upon the slope between these points the fold thus indicated 

 is clearly shown. The " mountain " is a bald massive hill, of 

 smooth and gentle slopes, rising 1000 feet above the eastern 

 base, with long rounded ridges on all side but the west. Prob- 

 ably the absence of projecting outcrops explains why it has re- 

 ceived so little attention from those who have repeatedly visited 

 Table Mountain. 



On the western face of Green Mountain, opposite the sum- 

 mit, upon a minor ridge and in a small ravine below it, is a 

 practically continuous outcrop extending from near the sum- 

 mit down to the base of the steeper slope. Owing to the fold, 

 mentioned above, 900 feet of strata are here exposed in a verti- 

 cal distance of 500 feet. These 900 feet of Denver beds are 

 not elsewhere preserved. At the bottom of this section is a 

 very marked dark conglomerate dipping 45° eastward. The 

 500 feet of fine-grained Denver strata below this conglomerate 

 are but poorly exposed near Green Mountain. They occupy a 

 narrow band between a definite horizon of the Willow Creek 

 beds and the dark conglomerate at the base of the described 

 outcrop. 



A second outcrop of great importance is at the southwestern 

 base of Green Mountain, where a ravine cuts diagonally across 

 vertical strata, giving a continuous section from the base of the 

 Denver beds, which is clearly shown, down through the entire 



