NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 67 



The following is a section given by Lee ^ near Exeter Post Office, in the 

 Canyon of the Rio Cimarron, northeastern New Mexico (abbreviated) : 



Feet. 



Dakota, hard quartz sandstone 73 



Morrison (?) shale, sandstone and Hmestone, .'.'.','.'.'..'. 200-20"; 



Shales. . • • • o 



Exeter, sandstone red and variable in color 7^ 



Unconformity. 



Red Beds, red sandstone interstratified with red and purple shales. 



Henderson ^ in 1 908 gave an account of the Permo-Triassic (?) of the foot- 

 hills formations of northern Colorado. He distinguishes the upper part of 

 the Wyoming as partly Permian. 



"Lykins Formation. — Conformably overlying the Lyons is a series of variegated, 

 mostly thin-bedded sandstones and shales, rather friable, chiefly deep red in color, 

 with thin limestone bands, the upper part usually gypsiferous. In the Boulder 

 district Fenneman names these beds the Lykins formation. It is the exact equiva- 

 lent of the upper Wyoming of Emmons in the Denver Basin and the Chugwater of 

 Darton in northern Colorado. In the Denver Basin monograph it is given a thick- 

 ness of 485 to 585 feet, Fenneman makes it 800 feet in Four-mile Canyon, north of 

 Boulder, and Darton gives it a thickness of 380 feet at Lyons and 520 feet at Owl 

 Canyon. Though it varies greatly in thickness and in stratigraphic details, its gen- 

 eral characters are constant throughout the region. As a whole the formation is 

 non-resistant, the greater part being concealed by the debris in the lateral north- 

 south valleys caused by its destruction. 



From Owl Canyon to the Little Thompson I have mapped as part of the Lykins 

 a more resistant sandstone, strongly cross-bedded, which forms a ridge in the valley 

 and which sometimes extends nearly to the top of the east slope of the Lyons escarp- 

 ment (plate 18, fig. i). It is difficult to distinguish from the Lyons sandstone, and 

 should perhaps be assigned to that formation, but is uniformly separated from the 

 latter everywhere north of the Little Thompson by strata lithologically resembling 

 the Lykins. In approaching Little Thompson Canyon these intervening beds rapidly 

 play out, bringing the sandstone which is mapped as Lykins into contact with the 

 Lyons and making the former the crest of the escarpment, almost covering the latter. 

 Thence southward it is doubtful if the two sandstones can be recognized as distinct 

 formations, and nowhere have I found a noticeable unconformity. As the two sand- 

 stones after coalescing form an almost vertical escarpment, if they are distinct it is 

 practically impossible to represent the Lyons on the map, yet northward they are 

 quite distinct. The one which is mapped as Lykins in the northern region passes 

 beneath the ' crinkled ' sandstone of Fenneman's report, which is but a few feet above 

 the Lyons north of Boulder. This problem is worthy of future investigation. 



' ' In some places certain strata of the Lykins are very massive, though soft, and por- 

 tions of the formation are locally calcareous, in addition to distinct limestone bands. 



"In the absence of paleontological evidence this formation has been usually 

 assigned to Triassic-Jurassic age. It seems quite likely, however, that the base of 

 the Lykins may represent Permian time, as the immediately underlying Lyons is 

 upper Carboniferous. The upper part of the Lykins is probably Triassic or Jurassic, 

 as it is overlaid by known Jurassic in northern Colorado, though it is possible that 

 part of the Jurassic and Triassic is represented by the general unconformity between 

 the Lykins and the Morrison." 



* Lee, Jour. Geol., vol. lo, p. 46, 1902. 



b Henderson, First Ann. Report Geological Survey of Colorado, 1908, p. 168. 



