54 WHLETS T. LEE 
Summary and conclusions.—It seems evident from the fore- 
going data that the shales lying beneath the Dakota sandstone 
in this region are found, with little variation in thickness or char- 
acter, from the foot of the Rocky Mountains eastward to Okla- 
homa and southward to the Canadian River wherever streams 
have cut deep enough to expose them. This persistency in 
thickness and general character exhibited by the shales wherever 
exposed, forces the conclusion that the formation was originally 
continuous, at least over the area represented by the accompa- 
nying map, and leads naturally to the inference that it extends 
far beyond these limits. The absence of paleontological data 
from the New Mexico areas leads to doubt concerning the 
integrity of the formation over the whole area. In the absence 
of such data, we must resort to stratigraphic and lithologic 
proofs. Since the shales lie between the Dakota above and the 
Red Beds beneath with apparent conformity except in the canyon 
of the Rio Cimarron, it may not be evident to those unfamiliar 
with the field relations that they compose a formation distinct 
from the Dakota on the one hand and the Red Beds on the other. 
Inthe Purgatory Canyon the contact is sharp between the Dakota 
sandstone and the Dinosaur bearing shales. In the Rio Cimar- 
ron and Canadian canyons there are equally sharp contacts 
between the upper sandstone and the underlying shales, and 
these are lithologically identical with the Dakota and the shales 
of the Purgatory. There is, therefore, little probability that the 
shales belong to the Dakota. 
There is even better evidence that they do not belong to the 
underlying formations. In the Purgatory and Rio Cimarron 
canyons they are separated from the Red Beds formation by a 
gypsum series which is here considered as representing the 
closing stage of the Red Beds period. As already stated, there 
is in the Rio Cimarron an angular unconformity between the 
shales and the Red Beds where the shales are seen resting upon 
the truncated edges of the upturned gypsum and underlying red 
strata. Where the Exeter formation occurs, the shales overlie 
it conformably, but the marked contrast between the two series 
