LAWRENCE — A new full-color map of Kearny County in southwestern Kansas featuring surface geology – from widespread silt deposits and active sand dunes to formations made up of Rocky Mountain debris – is available from the Kansas Geological Survey, based at the University of Kansas.
Surficial geology maps highlight the type and age of rock layers found on the surface or immediately below the vegetation and soil.
This revised map by KU Geography Professor William Johnson and Terri Woodburn, KU geography graduate student, features newly identified ancient terrace systems along the Arkansas River and numerous playa lakes that give rise to transient wetlands, among other updates to Johnson’s 2003 Kearny County map.
The ephemeral playa lakes, fed only by precipitation and runoff, range in size from less than an acre to hundreds of acres and are scattered throughout the county’s uplands. Also known as lagoons or buffalo wallows, the shallow playa basins help recharge the underlying High Plains aquifer and provide refuge for local and migratory wildlife when filled.
Most of the playas are in areas covered with loess, or windblown silt, deposited within the last 100,000 years. Loess covers a large portion of the county, especially in the area north of the river and in the southwest corner.
Active sand dunes and subdued swells and swales of sand sheets are located mostly south of the river.
“Sand dunes in the county have been active off and on during the last 15,000 years or so,” Johnson said. “Prehistoric dune activity was usually far more severe than during the 1930s Dust Bowl.”
Resources extracted from open sand and gravel pits shown on the map in the alluvial deposits are used for road surfacing and concrete construction.
Lakin and Deerfield, the county’s two incorporated towns, are located in the Arkansas River terrace deposits, which are made up mainly of course gravel with some sand and silt. The terraces are remnants of previous floodplains cut down through by the current river channel and its floodplain.
Outcrops of the Ogallala Formation are adjacent to the county’s floodplains. Locally known as mortar beds, these outcrops consist of consolidated sand, gravel and clay transported in by streams from the Rocky Mountains about 5 million years ago.
The water-bearing portion of the Ogallala Formation, known as the Ogallala aquifer, extends throughout much of western Kansas and makes up a large part of the massive High Plains aquifer system.
Decreases in ground-water levels in the High Plains aquifer, the major source of water in western Kansas, have caused declines in the Arkansas River, which used to gain water from the aquifer but now loses water to it.
Besides the Arkansas River, its tributaries, and several draws, surface-water features on the map include the Great Eastern Ditch, the Amazon Ditch and Lake McKinney, constructed in the late 1800s and early 1900s to transport and store the river’s water for irrigation. From its completion in 1908 until 1948, Lake McKinney was the largest lake in the state.
In addition to geologic and hydrologic characteristics, the map includes towns, roads (from Federal highways to unimproved roadways), elevation contours at 10-meter intervals, and township and range boundaries.
Drawn in full-color to differentiate rock layers, the computer-generated geologic map features shaded relief to give the map its three-dimensional look and emphasize the landscape's topography. The map is at a scale of 1:50,000 so that one inch on the map equals about 3/4 mile of actual distance.
Besides the map, the 50" x 44" sheet contains an illustrated rock column, which shows the order in which the rock units were deposited over time, and a description of each unit.
Copies of the Kearny County map are available from the Kansas Geological Survey at 1930 Constant Ave., Lawrence, KS 66047-3724 (785-864-3965 or email@example.com) and at 4150 W. Monroe St., Wichita, KS 67209-2640 (316-943-2343 or email firstname.lastname@example.org).
The cost is $15 plus shipping and handling. Inquire about shipping and handling charges and, for Kansas residents, sales tax.
More information about the maps and other KGS products is available at www.kgs.ku.edu.
For more information, contact Bill Johnson, (785) 864-5548 or email@example.com.