348 WILLIS T. LEE 



of the sandstones. The relative amount and position of sand- 

 stones, shale and limestones at any one point is no indication 

 that a similar relation will be found at any other point. There 

 is no abrupt lateral change, but the various beds blend into each 

 other or pinch out laterally in a gradual though somewhat rapid 

 manner, so that, while no sudden change is seen, a comparison 

 of sections a few miles apart may show a total change in kind 

 and relation of materials. The Dinosaur bones to be described 

 later were found in the shales at nearly every horizon. Aside 

 from these, no fossils were found. Careful search at every 

 horizon failed to reveal a single invertebrate. 



The three formations — the Red Beds, the shales, and the 

 Dakota sandstone — are apparently conformable. There seems, 

 however, to be some indication of a break between the gypsum 

 and the shales, and still more between the shales and the 

 Dakota sandstone. The red sandstone, as already pointed out, 

 passes upward through shales into the gypsum by a gradual 

 transition. There was no evidence found, at any of the places 

 examined in detail, of a break in deposition between the red 

 rocks and the gypsum. At the top of the gypsum the evidence 

 is not so satisfactory in every case. In Red Rocks Canyon the 

 change is abrupt from gypsum to sandstone ; but in Plum Canyon 

 and elsewhere the upper layer of the gypsum beds is shale con- 

 taining irregular masses of gypsum. This is overlain by the 

 variegated shales. The gypsum beds vary in thickness from 

 20 to something like ioo feet. In some places, at least, as 

 shown in the sections given in this paper, the shales increase in 

 thickness as the gypsum decreases, and vice versa. It is possible, 

 therefore, that the gypsum beds were exposed and slightly 

 eroded previous to the deposition of the shales. However this 

 may be, it seems clear that the gypsum belongs to the Red Beds 

 series, and probably marks the closing stage of the Red Beds 

 period. If this interpretation be correct, there is no gypsum in 

 any part of the shale formation of southeastern Colorado, so far as 

 known. The contact of the shales with the Dakota sandstone is 

 more plainly marked, and in places exhibits gentle undulations, 



