Hatchek : TiiK Jurassic Dinosaur Deposits. 329 



designated this series as the Fountain formation and referred it to the 

 Carboniferous on the evidence afforded by certain fossils found in cer- 

 tain thin seams of limestone interstratified with a similar red sandstone 

 found in the western part of Colorado. Thus far no fossils are known 

 from the red sandstone of Garden Park, and until we have some direct 

 evidence as to their age it would seem as well to correlate them with 

 the " red beds " everywhere so abundant about the eastern slopes and 

 outliers of the Rockies and which have of late been generally con- 

 sidered as of Triassic age. These sandstones dip very gently to the 

 southeast and pass beneath the surface at a point a little above the 

 southern entrance to Garden Park. In their lower members they are 

 of a uniform brick red color, fine grained, and do not differ materially 

 from the Triassic sandstones found everywhere flanking the main 

 ranges of the Rockies as well as surrounding all the detached or isolated 

 upthrusts belonging to the same great mountain system, except for a 

 decrease at this locality in the quantity of gypsum or selenite which 

 usually 'accompanies the Triassic red beds of the West. Toward the 

 top these sandstones become much harder, and coarser, the color is 

 not so deep a red and in places they pass, toward the summit, into a 

 very hard coarse-grained sandstone or conglomerate of a brownish gray 

 color. I have been unable to detect any unconformity between the 

 Triassic sandstones and the overlying Jurassic rocks in this locality, 

 although a careful search might reveal such. 



The Jurassic. 

 Immediately overlying the red sandstones are a series of brown 

 sandstones, shales and marls with occasional thin seams or lenses of 

 limestone. They have an aggregate thickness of perhaps 450 feet and 

 the whole is about equally divided between sandstones, and shales or 

 marls. The entire series is here referred to the Jurassic on the evi- 

 dence afforded by the dinosaur remains found in them. These re- 

 mains are found in considerable abundance at several horizons and 

 occur both in the sandstones and the shales, while the limestone 

 layers above referred to are as a rule very rich in the remains of 

 small fresh water gastropoda and from one horizon great numbers of 

 Unio shells and casts have been obtained in one of the marl beds. 

 These invertebrate remains have been described by Dr. C. A. White 

 in Bulletin 29 of the U. S. G. S. Unfortunately like most freshwater 

 invertebrates they afford little evidence as to the exact age of the 

 deposits from which they were derived. 



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