CB08B.J 



KXC'URSION TO GOLDKN. 



439 



horizon not far below the Dakota, and on the 

 slope facing the town of Morrison, Prof. Arthur 



Lakes found the first gigantic Dinosaur bones 

 upon which Prof. Marsh established the genus 



Atlantosanrns. Other remains of the same 

 animal have been found at this horizon, both 

 to the north aid south of Morrison, and also 

 at a corresponding position near Canyon City. 

 In the white Dakota sandstones and in a 

 lire clay bed in the middle of the sandstone 

 section there lias been found an extensive fos- 

 sil flora which has been made the subject-mat- 

 ter of a monograph by Prof. Lesqnereux, pub- 

 lished by the U. S. Geologieal Survey. The 

 section of Fort Benton shales immediately 

 overlying the Dakota is most clearly seen on 

 the south bank of Pear creek, along .the line 

 of an irrigating ditch. 



The small ridge at the base of the Dakota 

 hogback iscausedbythe Niobrara limestones 

 and the entire section of the Niobrara is very 

 well shown in the part of the section illus- 

 trated. 



Following the Niobrara comes a great thick- 

 ness of Fort Fierre shales, which, along Pear 

 creek, have a thickness of over 5,000 feet. 

 while in the section running from the sum- 

 mit of Green mountain, about three miles to 

 the northward of Pear creek, their thickness 

 is reduced to a few hundred feet. From the 

 observed variation in the thickness of these 

 beds, together with the visible divergence of 

 strike in this interval, Mr. Fldridgehas estab- 

 lished a considerable unconformity between 

 the Niobrara and Fort Pierre. 81 



Above the Fort Pierre come the shales of 

 the Fox Hills in their normal development. 

 At the western ba8e of Green mountain is a 

 small but distinct ridge of the Laramie sand- 

 stones (<l, Fig. li<>) in vertical position, con- 

 taining coal beds, here of less than the nor- 

 mal thickness. T his line of the Laramie beds 

 is clearly traceable along the southern slopes 

 of Green mountain, running parallel to the 

 band representing the Fox 'Hills, and crosses 

 Bear creek at a hill called Mount Carbon 



WA 



M 



•Vfrfc 



$ 





$ 



r 



M 



K 



•> 



J 



