352 WILLIS T. LEE 



known as Mesa de Maya. It is a part of the volcanic region 

 extending from the mountains eastward along the southern 

 border of Colorado. This mesa is separated from the equally 

 elevated region of northern New Mexico by the canyon of the 

 Cimarron, which is cut not only through the basalt and the 

 Dakota, but deep into the Red Beds. Here, as further north, 

 a shale formation lies between the Red Beds and the Dakota. 

 At the one point studied gypsum occurs near the top of the Red 

 Beds, but a thick stratum of red sandstone lies between it and 

 the overlying shales. The shales correspond closely in charac- 

 ter and general appearance with those further north, although 

 they are more arenaceous and thicker (about 350 feet). No 

 fossils of any kind were found, but enough was seen of the for- 

 mation to warrant the inference that it is probably the same as 

 the formation which occurs in the same position in the canyon 

 of the Purgatory, thirty miles further north, viz., the Morrison. 



SUMMARY 



1. From the foregoing considerations it appears that the 

 stratigraphic, lithologic, and paleontologic evidence all point to 

 the inference that the shales of southeastern Colorado are of 

 Morrison a^e. It is inferred, furthermore, that this formation 

 extends from its line of outcrop along the flank of the Front 

 Range, underneath the Dakota, as far east as Smith Canyon, 

 about seventy-five miles, and as far south as the canyon of the 

 Cimarron. How much further it extends in these directions is 

 not determined. 



2. Although there are gypsiferous shales lying between the 

 gypsum and the fossiliferous shales, which might seem at first 

 thought to form a transition, it is thought that the line of demar- 

 cation should be drawn at the top of the gypsiferous shales. If 

 this division be correct, there is no gypsum in the Morrison for- 

 mation of southeastern Colorado. In this it differs from that for- 

 mation as reported from some localities. The gypsum is here con- 

 sidered as belonging to the closing stage of the Red Beds period. 



Willis T. Lee. 

 Trinidad, Colo. 



