Surficial
Geology and Stratigraphy
of Russell
County, Kansas
Alan F. Arbogast and William C. Johnson
Russell County is located in
north-central Kansas, within the Smoky Hills physiographic province, which
exhibits a wide variety of erosional and depositional landscapes. Outcrops range in age from Upper Cretaceous
to Holocene, including the Dakota Formation, Graneros Shale, Greenhorn
Limestone, Carlile Shale, Niobrara Chalk, Ogallala Formation, and several
unconsolidated Quaternary eolian and fluvial deposits. The Dakota Formation, consisting of deltaic
sandstones and mudstones, underlies the entire county but crops out primarily
in the eastern one-half of the study area.
The Graneros Shale is a thin formation of dominantly fissile shale,
poorly exposed, that crops out conformably between the Dakota and the overlying
Greenhorn Limestone. The Greenhorn
Limestone consists of transgressive beds of shale and chalk and crops out
countywide. Intensively dissected in
some areas, the Greenhorn limestone forms steep canyons where resistant beds of
chalk and chalky limestone, such as the Fencepost Limestone, are present. The Carlile Shale consists of two distinct
members in Russell County, the Fairport Chalk Member and the Blue Hill Shale
Member. Exposures of the Fairport Chalk
Member are common throughout the county but are thickest in the northwestern
corner, whereas the Blue Hill Shale Member is exposed only in the northwestern
corner of Russell County. Due to the paucity
of exposures, the Codell Sandstone Member of the Carlile Shale is not
differentiated from the Blue Hill Shale Member. Unconformably overlying the Carlile is the Niobrara Chalk, which
consists of two distinct members, the Fort Hays Limestone Member and the Smoky
Hill Chalk Member. Both members of the
Niobrara Chalk are confined to the extreme northwestern corner of Russell
County. Outcrops of the Miocene-age
Ogallala Formation, a sedimentary sequence of Rocky Mountain-derived fluvial
sediments, have been tentatively identified and are largely confined to the
northwestern corner of the county.
Quaternary deposits, ranging in age
from pre-Illinoian to Holocene, mantle much of Russell County, but are
generally poorly exposed. Pre-Illinoian
associations are tentative, consisting of the Grand Island and Sappa Formation,
and are based on the topographic position of upland gravel deposits. Illinoian stratigraphy consists of the Crete
Formation, Loveland Loess, and Sangamon Soil. Sands and gravels of the Crete
Formation are expressed as a high terrace along the major streams in the
county, but their distribution is uncertain.
The Loveland Loess is widely distributed in north-central Kansas and has
been recognized at one site in Russell County.
The Sangamon Soil, a major pedostratigraphic feature which caps the
Illinoian Loveland Loess, has been identified in Russell County. Overlying the Sangamon Soil is the
middle-Wisconsinan Gilman Canyon Formation and the late-Wisconsinan Peoria
Loess. The Gilman Canyon Formation is a
loess that accumulated at a sufficiently slow rate for the development of a
soil. Accelerated loess fall during the
late Pleistocene produced the Peoria Loess, which mantles the upland.
Holocene stratigraphic elements include the Brady Soil, Bignell Loess, modern surface soil, and fluvial deposits. The Brady Soil caps the Peoria Loess and is discontinuous in Russell County but is recognizable only where it is buried by Bignell Loess. Holocene fluvial deposits occur as fill in a high terrace and as post-1,000-yr B.P. floodplain sediments.