Fauna of the Morrow Group 
61 
and of variable thickness but always thinner than the Brent- 
wood. Midway between these two limestone lenses there is in 
many places a seam of coal ordinarily about eight inches, but 
in some instances as much as fourteen inches, thick. 
The three limestone horizons, in the Hale, the Brentwood, and 
the Kessler, are highly fossiliferous and contain the fauna 
which is the subject of this report. Associated with the coal 
seam in the Bloyd shale a fairly abundant fossil flora has been 
found. 
Westward and northwestward from the vicinity of Morrow 
the sandstones and shales of the Morrow group decrease in 
thickness and the formations become more calcareous, while to 
the eastward and northeastward the limestones decrease in im- 
portance and the group is composed almost exclusively of clastic 
sediments. In Oklahoma it is not practicable to subdivide the 
group and the whole series, composed dominantly of limestone, 
is known as the Morrow formation. 
Stratigraphic Relations of the Morrow Group 
The Hale formation, or the Morrow to the westward, rests 
unconformably upon the Pitkin limestone, or in a few places upon 
the Fayetteville shale which underlies the Pitkin. The group 
is overlain unconformably by the Winslow formation. Both 
of these unconformities are more apparent to the north than 
toward the southern part of the area where the rocks are 
exposed. Indeed, in the Winslow quadrangle the beds appar- 
ently succeed one another with complete conformability. Farther 
north, however, the erosion intervals before and after the deposi- 
tion of the group were more clearly recorded. In places the 
Pitkin limestone was entirely removed before the deposition of 
the Hale, while the variable thickness of the shales above the 
Brentwood horizon and the absence of the Kessler limestone in 
some places are attributable to the erosion which occurred before 
the grits and sandstones of the Winslow formation were accu 
mulated. 
The relations of the various formations of the region may 
be more easily understood if placed in tabular form. 
