Hydrogeology

A veneer of loess deposits and sand dunes cover the Rattlesnake Creek subbasin. The underlying Pleistocene alluvium forms the major aquifer of the area. The ancestral Arkansas River and a small number of local streams deposited the alluvium. It is composed of undifferentiated early and late Pleistocene sediments. The early Pleistocene sediments include the Meade formation. It consists of interbedded lenses of unconsolidated gravel, sand and silt. Caliche is also common in the formation. The late Pleistocene sediments include the Sanborn formation. It consists of silt, sandy silt and fine sand that locally contain lenses of coarse sand and gravel. The Pleistocene alluvium overlies Cretaceous and Permian bedrock. The lower reaches of the Rattlesnake Creek and the Quivira National Wildlife Refuge represent a natural ground-water-discharge area. It discharges water from both the unconsolidated Great Bend Prairie aquifer and the underlying bedrock aquifers.

The alluvium in the Rattlesnake Creek valley is relatively thin. It is probably less than 20 feet thick everywhere. It is composed chiefly of poorly sorted sand and gravel. Thick deposits of the Meade formation underlie the alluvium. The Meade formation provides the sediments for the alluvium. Hydrogeologically the two units are mostly indistinguishable.

Erosion removed most of the Tertiary deposits that make up the Ogallala Formation before Pleistocene material was deposited. The stratigraphy of the Quaternary alluvium in descending order is generally 1. sand dunes; 2. a relatively continuous near-surface silt-clay bed, probably a loess deposit; 3. alternating sequences of sandy silt-clay, and sand and gravel lenses; 4. a basal sand and gravel bed of fluvial origin; and 5. bedrock.

The Permian bedrock subcrops along an approximately north-south trend near US-281. It releases a source of poor-quality water east of US-281. The saline water is found in northeast Stafford County and other localities. The Permian formations in the area are known as red beds. They consist of reddish-brown sandstone, siltstone, shale, salt, gypsum, anhydrite and limestone. The Permian deposits, especially the Late Permian red beds, increase the salinity of the water in the unconsolidated aquifer in the lower reaches of Rattlesnake Creek. This is especially true in the Quivira National Wildlife Refuge.

Rocks of Cretaceous age form the bedrock surface in the western part of the Great Bend Prairie. These rocks consist of interbedded shales, sandy, shales and fine to coarse-grained sandstones. Of the three Cretaceous units, only the lower unit -- Cheyenne Sandstone -- is a potential source of water to large-capacity wells. This water is believed to be highly materialized. The Kiowa Formation is the oldest formation exposed in the Rattlesnake Creek subbasin. It is in the northwestern part of T. 22 S., R. 11 W. in northeastern Stafford County. It consists of dark fossiliferous shale and rusty sandstone. The overlying Dakota Formation is not exposed in the subbasin area.

The Pleistocene drainage patterns of central Kansas record the history of the northeastward migration of through-flowing streams from the Rocky Mountain area. This migration was caused by successive captures of the southern trunk of the ancestral stream by its own northern tributaries. The captures seem to have resulted from the difference in the debris load available in the headwater areas of the streams. Throughout the Pleistocene, through-flowing streams originating from the Rocky Mountains, such as the Arkansas River, filled their channels with coarse gravel and sandy alluvium derived from igneous rocks. This material built up the surface over which the streams flowed. This caused stream avulsions. As a result, alluvial material spread over wide areas. In contrast, the sediment load obtained by downcutting in their immediate headwater areas. The silt and fine-grained sand of local origin in the northern Great Bend Prairie with its low permeability favored runoff. Consequently, there is more erosion and downcutting to below the level of the through-flowing streams. This downcutting led to the eventual capture of the through-flowing streams. This is evident in the relative abundance of northern tributaries to the Arkansas River in central Kansas.

Source: Final Report for the Computer Model in the Rattlesnake Creek Basin

Kansas Geological Survey and Kansas State University, May 1997