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  Ford County Geohydrology

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Table of Contents

Abstract

Introduction

Geography

Geology

Ground Water

Formations

Well Records

Logs of Test Holes

References

Plates

 

Geology

Summary of Stratigraphy

The rocks exposed in Ford County are of Quaternary, Tertiary, and Cretaceous age. The areal distribution of the formations is shown in plate 1. The oldest formation cropping out in the county is the Dakota formation. It is best exposed along Sawlog Creek in the northern part of the county and on the north side of Arkansas River in the vicinity of Ford. The overlying Cretaceous formations, represented in this area by the Graneros shale and the Greenhorn limestone, are best exposed in the northern part of the county where tributary streams have cut beneath the overlying Tertiary deposits. The uppermost beds of the Cretaceous are absent in Ford County. The Ogallala formation of Tertiary age, which rests unconformably on the Cretaceous rocks, mantles a large part of the county, but south of the river it is largely covered by younger deposits. The Pleistocene water-laid deposits of the Kingsdown formation constitute the surface material of a broad area south of the Arkansas valley. The plains surface is mantled both north and south of the River by deposits of loess of variable thickness, ranging in age from Pleistocene to Recent, which form the upper part of the Kingsdown silt. Dune sand occupies a belt of varying width bordering the south side of Arkansas River and also mantles other isolated tracts. The soils, alluvium, drifting dune sand, and terrace deposits are the most recent deposits in the area.

The character and groundwater supply of the geologic formations in Ford County are described briefly in the following generalized section (table 1) and in more detail under "Water-bearing formations."

Table 1--Generalized section of the geologic formations of Ford County, Kansas.

System Series Subdivision Thickness (feet) Character Water Supply
Quaternary Pleistocene and Recent Alluvium and Terrace deposits 0-60 Sand, gravel, and silt, comprising stream deposits in the Arkansas valley and in the valleys of many smaller streams. Coarse gravels occur as terrace deposits bordering the present flood plain of Arkansas River at levels 15 to 25 feet above the flood plai The alluvium yields large supplies of water to wells in the Arkansas valley and lesser amounts in the smaller stream valleys; supplies many irrigation wells in the Arkansas valley. Some waters from the alluvium are very hard, containing from 238 to 1,413
unconformable on older formations
Dune sand 0-70 Fine eolian sand. Except where reopened by recent blowouts, the dunes are well stabilized by vegetation. Probably does not supply water directly to wells, but constitutes favorable catchment area for ground-water recharge to adjacent and underlying formations.
unconformable on older formations
Kingsdown silt 0-135 Predominantly light buff, even-bedded soft silt and clay containing small, scattered lime nodules; contains unstratified loess in its upper part which grades gradually upward into loess of Pleistocene and Recent age. Contains light-colored sand and gravel Yields little or no water in its upper part, but sand and gravel deposits near the base may furnish some water to wells where the water table lies above them. Most of the Kingsdown silt is dry and relatively impermeable.
disconformity
Tertiary Middle and upper Pliocene Ogallala formation Rexroad member 20-250 Alternating beds of gray to greenish clay, buff-colored sandy silt, and rusty sand and gravel. Gravel contains many large-sized pebbles and water-worn fragments of caliche. Has not been recognized north of Arkansas River. (May contain some beds in upper p Yields good supplies of water to most of the wells located on the uplands south of Arkansas River, including most of the irrigation wells.
disconformity
  Gravel, sands, silts, caliche and structureless silt and silty sand with hard and soft layers of sandstone and conglomerate, south of which is cross-bedded and cemented with lime. Gravel and coarse sand are abundant in the basal part, and lime-cemented be The principal source of water supply in many parts of the county. Yields adequate supplies of water of good quality to domestic, stock, municipal, and industrial wells. Supplies water to many irrigation wells, particularly to deep wells in the Arkansas va
unconformable on older formations
Cretaceous   Greenhorn limestone Pfeifer shale member 20 +/- Chalky shale with beds of thin chalky limestone, discoidal concretions, and thin beds of bentonite. "Fencepost" limestone at top. Very few wells obtain water supplies from the Greenhorn limestone in the county. Only very limited supplies of comparatively hard water may be expected from wells penetrating this formation. In general, the water is hard, ranging in hardness from about 35
Jetmore chalk member 20 +/- Alternating beds of chalky shale and chalky limestone, "Shell" limestone at top.
Hartland shale member 80 Chalky shale with a few thin beds of chalky limestone and bentonite.
Lincoln limestone member Yellowish chalky shale with hard, thin-bedded, finely-laminated, crystalline limestone at top and bottom, and a few thin beds of chalky limestone.
Graneros shale 43-45 Dark bluish-black, fissile, noncalcareous clay shale with numerous thin lenses of sandy shale, sandstone, and interbedded ironstone concretions. Outcrops are strewn with selenite crystals. Practically barren of water; no wells are known to derive water supplies from this formation in the county. Any water that might be encountered probably would be highly mineralized and very bitter to the taste.
Dakota formation 56-235 Fine-grained, gray to white to yellow-grained, quartz sandstone with interbedded bluish-gray, silty and sandy shale. Yields moderate supplies of water of good quality to wells in the northeastern part of the county. Several irrigation wells in the extreme southwestern corner of the county tap the Dakota, but obtain most of their water from the overlying Ogallala formati
Kiowa shale 44 + Black to bluish-black to gray to yellowish-gray argillaceous shales with a few thin beds of yellowish or pinkish limestone. Not exposed in county. Not known to yield water to wells in Ford County.
Cheyenne sandstone 70 + Light gray to yellow, fine to coarse-grained, quartz sandstone with interbedded bluish-gray, silty ad sandy shale Not known to yield water to wells in Ford County.
unconformity

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  Kansas Geological Survey, Ford Geohydrology
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Web version April 2002. Original publication date Dec. 1942.
URL=http://www.kgs.ku.edu/General/Geology/Ford/04_geol.html