News Release, Kansas Geological Survey, May 15, 1996
The full-color map and report are by geographers William Johnson at KU and Alan Arbogast, a former KU geography graduate student, now teaching at Michigan State University.
Because Russell County is one of the state's leading producers of petroleum, geologists already know much about the deep underground geology of Russell County from wells drilled in search of oil. The new map and report focus more on the geology at the earth's surface, showing the type of bedrock in Russell County.
Maps of near-surface geology are a beginning point in planning, construction, location of natural resources such as water or building stone, and a variety of environmental activities. The Russell County map is one in a series of new geologic maps being produced by the Survey.
Much of the bedrock exposed at the surface in Russell County was deposited during the Cretaceous Period of geologic history, from around 90 to 70 million years ago when the western half of the state was covered by an interior sea.
"The Fencepost limestone and the Dakota sandstone are probably the best-known rock units that crop out in Russell County," said Johnson. "The Dakota is familiar because of the orange and dark red sandstones that crop out, for example, around Wilson Lake. The Fencepost is known for its use as a building stone in bridges, buildings, and, of course, fenceposts."
The Dakota Formation is made up of sandstones, clay, and shales that were deposited about 90 million years ago by rivers and along the beaches of that Cretaceous sea. The Fencepost limestone is one layer in a rock unit known as the Greenhorn Limestone that was deposited shortly after the Dakota at the bottom of that shallow Cretaceous sea.
Other layers of limestone and shale, all deposited during the Cretaceous, crop out in Russell County. The youngest is the Niobrara chalk, which crops out in a small area in the county's northwestern corner. The Niobrara is famous for producing fossils of sea-going animals.
"The Cretaceous Period was toward the end of the time of the dinosaurs, and you can find Cretaceous fossils in many of the rock units in Russell County," said Johnson. "Because the area was covered by a sea, you usually find marine fossils, such as clams, fish, and sharks teeth."
More recent geologic formations also show up in Russell County. The Ogallala Formation, deposited in the last 10 million or so years, caps hills and crops out along hillsides in northwestern Russell County. Even younger deposits of sand and gravel, silts, and ancient soils are found along many of the county's rivers.
In addition to the surface geology, the map shows the county's towns, roads, lakes, railroads, and other features. The map measures about 46 inches by 48 inches and is drawn at a scale of 1:50,000 so that one inch on the map equals about three-quarters of a mile of actual distance.
Copies of the new map and report are available from the Kansas Geological Survey, West Campus, University of Kansas, Lawrence, KS 66047 (or phone 785-864-3965). The cost is $15.00 for the map, $10.00 for the report, plus $5.00 for handling. Kansas residents should add 6.9% sales tax.