GEOLOGY AND PALEONTOLOGY. 157 
growing along the sand covers that part of the rock over which the water runs 
in little rills.’’>* 
Springs issue along the high banks above Decatur, and also near the mouth 
of Blackbird creek. At the old mission building, two miles north of this creek, 
there is a spring, famous long before the arrival of white men. At Homer, along 
the bluffs north and south of the city, there are some of the strongest springs 
known in the formation, and they continue past Ponca and as far up the river as 
the Dakota is found. 
SALT SPRINGS AND MARSHES. 
While the fresh-water springs of the Dakota are found in all parts of the group, 
the salt-springs, on the contrary, are ordinarily confined to the upper beds. Mr. Lo- 
gan locates a salt-marsh horizon above the lignite horizon in his upper group, 
and describes it as follows: ‘‘ Resting upon the lignite is a bed of shales which 
are, in the majority of instances, highly saliferous in character. They vary in 
thickness from ten to fifteen feet. By the disintegration of these shales, salt- 
marshes have been formed along the exposures of the upper Dakota horizons.’’ * 
There are a dozen or more of these marshes in north-central Kansas, located 
in Lincoln, Mitchell, Cloud, Republic, and Jewell counties. In size they vary 
from a few square rods to several square miles in area. One in Cloud county is 
seven miles long, and, in places, a mile wide. They are usually found along the 
basin of one of the numerous creeks in the region, and are at nearly the same 
geological level—from 50 to 100 feet below the base of the overlying Benton. 
The marshes are flat and are covered with an incrustation of salt, sometimes a 
quarter of an inch thick. The water comes from numerous small seepage springs 
along the margin or on the bottom. The soil is permeated with this salty water, 
a3 may be demonstrated by digging a hole in the bank. This soon fills with salt- 
water which shows a density of from ten to twenty degrees on the salometer. 
A description of one of these marshes will be good for a large number of them, 
as they are very similar in formation and appearance. The following, which is 
excerpted from a description made by Prof. B. F. Mudge in 1864, will, with a 
few minor modifications, answer for any one of a dozen marshes to-day. The 
marsh described is known as the Tuthill marsh, and is located in the southern 
part of Republic county, Kansas: 
‘‘The valley here is wide, gradually rising to the high prairies so common in 
that part of the state. The marsh covers nearly 1000 acres, more or less im- 
pregnated with saline matter. About one-third is entirely void of vegetation, 
which the brine will not allow to grow. It is perfectly level, and when first vis- 
ited was as white as a wintry snow field, with a crust of crystallized salt. The 
marsh is of recent alluvial formation, composed of sand and loam from twenty 
to thirty feet in thickness, brought down by the wash from the high prairies, 
which gradually rise from three sides. The incrustation of salt is frequently 
three-eighths of an inch thick. The brine exists in nearly equal quantities and 
strength in all parts of the marsh, and can be obtained by boring a few feet. No 
definite salt-spring shows itself on the surface, but the supply must come from 
numerous points below.’’ 
The chief difference between this description and one made to-day would be 
in the size of the marsh. The increased amount of alluvium incident upon the 
cultivation of the adjacent region has so encroached upon the marsh as to ma- 
terially lessen its area. Nevertheless, several hundred acres are still sufficiently 
saline to be without vegetation. Wells bored on land above the common level 
furnish brine which flows from the top of the well out over the marsh. On Salt 
54. Memoires de la Societe Helvetique des Sci. Nat., vol. XXII, No. 1, p. 5. 
55. Univ. Geol. Sury. of Kansas, 2: 209. 
