GEOLOGY AND PALEONTOLOGY. 139 
States Geological Survey, part IV, pl. txxx11, for those of Nebraska. The 
first map is by Haworth and the second by Darton. The foregoing reduced map 
of the two states is intended to show graphically the exposures throughout the 
entire region discussed in this article. The stippled portions indicate Dakota 
areas. 
STRATIGRAPHY. 
LINE OF UNCONFORMITY. 
The line between the Paleozoic and the Mesozoic rocks in Kansas and Ne- 
braska is one of unconformity. The Triassic and Jurassic rocks are totally want- 
ing, unless they are represented in the upper part of the Red-beds of Kansas and 
Oklahoma.‘*® The Carboniferous rocks in the eastern part of the two states 
grade upward through the Permian to the point of unconformity. From this 
line the Cretaceous formations succeed each other in regular sequence to the 
western limits of the states, and far beyond. The rocks of both great eras, Paleo- 
zoic and Mesozoic, thicken to the south. On the Oklahoma line there are some 
2200 feet of strata between the upper part of the Carboniferous and the base of 
the Cretaceous. At the Kansas-Nebraska line there are not to exceed 200 feet, 
while at the mouth of the Platte river the Dakota rests directly upon the upper 
surface of the eroded Carboniferous. In the Belvidere region the Cretaceous 
rocks below the base of the Dakota measure 250 feet, in central Kansas they are 
not more than 100 feet thick, while at the Nebraska line the Dakota rests directly 
upon the Permian. 
In other words, there are on the Oklahoma line about 2500 feet of strata be- 
tween the top of the Carboniferous proper and the base of the Dakota, while on 
the Platte river these beds have been entirely eroded away and their place is rep- 
resented by a hiatus; the sandstones of the Dakota resting upon and filling up 
the hollows of the old Carboniferous floor. This fact was commented upon by 
Doctor Hayden, who, although he had not all the facts at command, yet lays 
especial emphasis on the uneven erosion of the Carboniferous during Triassic 
and Jurassic time. Beyond the limits of the territory discussed in this article 
the amount of pre-Cretaceous erosion is still more strongly marked. In Iowa the 
brown, leaf-bearing sandstone rests unconformably upon the middle, or perhaps 
the Lower Carboniferous, and in Minnesota the Dakota is found in the hollows of 
the Trenton or even of the Cambrian. 
The superjacent strata are also quite varied. In the southern part of the area 
the Dakota is covered with the Tertiary. In McPherson county, Kansas, the 
Equus beds cap the group south of the Smoky Hill river. From near the state 
line throughout the entire state of Nebraska, all the older formations are covered 
with a mantle of glacial deposits. All of these rest unconformably upon the 
Dakota. From the Arkansas river to Iowa the Dakota is everywhere superseded 
conformably by the Benton and this by the Niobrara. 
Plate VII shows the relative position of the various formations contiguous to 
the Dakota in Kansas and Nebraska. Continuous lines represent unconformity. 
BASE OF THE DAKOTA. 
A question which might prove a vexing one, did we permit ourselves to con- 
sider it such, is that of the line of separation of the Dakota from the sub- and 
superjacent Cretaceous groups. At first glance it would seem necessary that a 
46. Since the above was written, it has been demonstrated that the upper part of the prob- 
lematic Kansas-Oklahoma Red-beds is Triassic. Vertebrates taken from the lower part of 
these beds, in eastern Oklahoma, have been identified by Dr. S. W. Williston as Permian forms, 
similar to those fromthe Texas Permian. On the other hand, invertebrates obtained from near 
the top of the Red-beds in western Oklahoma are classed as Triassic forms, on the authority of 
Dr. J. W. Beede and Mr. Charles Schuchert. The line of separation between the two series of 
rocks has been drawn provisionally at the heavy ledge of gypsum that caps the Gypsum Hills of 
Kansas and Oklahoma. See First Biennial Report of the Dl ahouts Geological Survey. ; 
