440 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



throe miles east of Morrison. Here the coal banks have become thicker 

 and have been opened in several mines. 



Green mountain will always remain a classic locality for the post- 

 Laramie lake beds which have been named the Arapahoe and Denver 

 formations. In a small ravine on the southwest slope of (Jreen moun- 

 tain, whose course is almost toward the point of view in the section 

 given, one may see an almost continuous exposure of the Laramie and 

 Arapahoe beds in vertical position. It was in this ravine that the iirst 

 pebbles of Dakota conglomerate, and other Meeozoic sandstones were 

 detected in the conglomerate, which is the most conspicuous feature of 

 the Arapahoe series. From this ravine the Arapahoe conglomerate 

 can be traced southward in practical continuity to a point several miles 

 south of the Platte canyon, and northward to Golden, although in the 

 latter direction it is less well marked, owing to the smaller size of the 

 pebbles. 



The main mass of Green mountain is made up of Denver beds. Con- 

 tact with the Arapahoe beds is most clearly indicated in the ravine 

 first mentioned and in others on the western slope of the mountain- 

 the lower 200 or M){) feet of the formation are, however, not very con 

 tinuously exposed in any section. Hut a characteristic conglomerate 

 composed of dark andesitic pebbles is clearly shown at the western 

 base of the more abrupt slopes of the mountain, and from this horizon 

 to the summit there is an almost continuous section illustrating very 

 clearly the characteristics of the formation. The coarse Conglomerates 

 of the upper part of the Denver formation are here so loosely consoli- 

 dated that the mountain summit and upper slopes aie covered with 

 loose boulders, which were not originally identified as belonging to a 

 definite formation in place, but considered drift boulders. For details 

 concerning the exposures of the Denver and Arapahoe formations in 

 Green mountain the reader is referred to the original article 79 on the 

 Denver Tertiary formation and the accompanying ma]), in which the 

 location of the section ravine and the. best exposures are clearly indi- 

 cated. The outcrops of the Denver formation are shown at intervals 

 along the banks of Bear creek and its junction with Platte river. 

 Many Dinosaur bones, referred by Prof. Marsh to the Ceratopsi(he, 

 have been found in the Denver beds on the western slopes of Green 

 mountain and in the plains area between that and the Platte river. 



