News Release, Kansas Geological Survey, Dec. 26, 1995
The map, the first highly detailed depiction of the geology of this south-central Kansas county, was compiled by Survey geologist Dan Merriam. Because it shows the type of bedrock at or near the surface, the map is useful in construction and engineering, environmental projects, water-well drilling, and almost any activity that involves excavation in the shallow underground. Because soils and geology are so closely connected, the map also has agricultural uses.
As shown on the map, most of the rocks at the surface of Chautauqua County were deposited during the Pennsylvanian Period of geologic history, about 300 million years ago.
Particularly noticeable in the eastern third of Chautauqua County are many sandstone layers, the remains of sand that was deposited in river channels and along ocean beaches during the Pennsylvanian Period. Today those sandstones cap many of the hills, creating an area of rolling topography that geologists have labeled the Chautauqua Hills. The vegetation on those sandstone-capped hills is an unusual pattern of blackjack oak and hickory hardwood forests that are known as "cross-timbers."
"The combination of unusual geology and vegetation makes the Chautauqua Hills one of the unique regions of Kansas," said Merriam.
Much of the western two-thirds of the county, according to Merriam, is covered by rocks deposited slightly later in the Pennsylvanian. Many of those younger Pennsylvanian rocks are limestones and shales, the same formations that crop out at the surface in Shawnee and Douglas counties.
"The rocks that crop out across central Chautauqua County are part of a formation that is termed the Oread Limestone," said Merriam. "So the rocks you see around Sedan are from the same geologic units as the rocks that cap Mount Oread in Lawrence."
Rocks of Permian age, deposited about 250 million years ago, are at the surface in the extreme northwestern and southwestern corners of the county. Rocks of that age are characteristic of the Flint Hills to the west, and Cedar Vale, in western Chautauqua County, is sometimes referred to as the "gateway to the Flint Hills."
Much younger deposits, mostly silt, sand, and gravel, are shown in the areas neighboring the rivers and streams that drain the county.
The map also shows several faults, or locations where layers of rock have moved relative to each other, in the subsurface of central Chautauqua County, a few miles west of Sedan.
In addition to the geology, the map shows the county's rivers and streams, lakes and ponds, roads, towns, and highways. The full-color map measures about 46 inches by 30 inches and was drawn at a scale of 1:50,000, so that one inch on the map equals about 0.8 of a mile in actual distance.
Copies of the map are available from the Survey's Publications Sales Office, West Campus, University of Kansas, Lawrence, KS 66047. The cost is $15, plus $4.00 postage and handling. Kansas residents should add 6.9% sales tax.