THE DENYKI! FOKMATION. 155 



tion, the .Monument Creek. Enterruptions to this succession are due to 

 topographical can p es and to the lacustrine character of the bodies of water 

 in which the sediments were laid down. 



SECTION II.— THE DENVER FORMATION. 



By Whitman' ( IROSS. 

 INTRODUCTION. 



The Denver formation is the most recent one now remaining in the 

 greater part of the district, and its strata form the surface, excepl when 

 covered by drift or Pleistocene deposits. Owing to their soft and friable 

 nature this fact does not insure the existence of outcrops suitable for the 

 study of the formation, and this superficial position of the strata has, 

 moreover, caused them to be especially subject to erosion, and the greater 

 part of the formation affected by the fold along the foothills has Keen 



removed, so that no complete section across the Upturned edges now 



remains, while such profiles are available tor nearly all the underlying 



formations. Except lor the protection afforded to a pail of the strata by 



the basaltic sheets of Table Mountain, and for the fortunate preservation 

 of other strata in the mass of Green Mountain, we should now he wholly 

 without data concerning the greater part of this most interesting formation. 



Geographical extent of the formation. Almost tile entire kllOWll area (if tile Deliver 



formation is included within the limits of the accompanying map. It now 

 covers an area of aboui 400 square miles. Roughly stated, the formation 

 extends from a line along the western bases of Green and Table mountains 

 eastward, embracing the" entire Mock between ( dear and Bear creeks and 

 continuing to the east line of the map, with Coal Creek as the northern 

 boundary, and the high lands of the overlying Monument ('reek beds as 

 the southern limit of the exposed strata. Small areas north of ( dear < 'reek 

 and south of Bear ('reek are also of Denver beds. 



concise characterization. — The Denver formation is characterized by the nature 

 of the material composing its sediments. While its strata are texturallv 

 very similar to those of the underlying Arapahoe formation, they are 

 essentially different in composition. The Arapahoe beds contain little 



