| System |
Series |
Subdivision |
Thickness (feet) |
Physical character |
Water supply |
| Quaternary |
Recent and Pleistocene |
Alluvium and terrace deposits |
0-68 |
Very coarse gravel, sand, and silt comprising stream deposits in the Arkansas Valley, Pawnee valley, and the valleys of other smaller streams. Very coarse gravels occur as terrace deposits along the Arkansas and Pawnee valleys. Terrace gravels occur benea |
The alluvium yields large supplies of water to wells in the Arkansas valley and lesser amounts in the other stream valleys; supplies many irrigation and a few industrial wells in the Arkansas valley. Some waters from the alluvium are very hard, containing |
| Unconformable on older formations |
| Dune sand |
0-70 |
Fine- to medium-grained wind-blown sand. Covers a large area south of the Arkansas valley and occurs in smaller areas north of the Arkansas valley. |
Occurs above the water table; therefore, it yields no water to wells. The dunes, however, serve as important catchment areas for recharge from local precipitation |
| |
Unconformable on older formations |
| Pleistocene |
Undifferentiated deposits |
0-300+ |
Consolidated and unconsolidated lenses of clay, silt, sand and gravel that are lithologically similar to materials of the Ogallala formation. Contain nodules and beds of caliche and locally volcanic ash. |
The sands and gravels of the Ogallala formation and Pleistocene undifferentiated beds are the most important sources of water in Finney and Gray counties. Most of the domestic and stock wells on the uplands, many of the irrigation and industrial wells, an |
| |
|
Unconformable on older formations |
| Tertiary |
Pliocene |
Ogallala formation |
0-250 |
Calcareous silts, sands, and gravels, much of which is cross-bedded. Both consolidated and unconsolidated. Contains nodules and beds of caliche. |
| |
Unconformable on older formations |
| Lower Pliocene and Upper Miocene (?) |
Laverne (?) formation |
0-91.5 |
Tan, brown, and gray silty blocky clay and clay shale, containing some medium-grained sand to fine gravel. Encountered only in test holes 15 and 16 in southern Finney County. |
Sands and gravels locally are potential sources of water supply, but they have not been exploited because of their great depth. |
| |
|
Unconformable on older formations |
| Cretaceous |
Gulfian* |
Smoky Hill chalk member (No rara formation) |
0-225 |
Alternating beds of soft chalky shale and chalk containing some thin beds of bentonite. Not exposed in Finney and Gray counties. |
Relatively impermeable. Not known to yield water to wells in Finney and Gray counties. |
| Fort Hays limestone member (No rara formation) |
55-80 |
Thick massive beds of chalk and chalky limestone separated by thin beds of chalky shale. Exposed over wide area in northeastern Finney County. |
Supplies limited amount of water to few wells and springs in Finney County. Water occurs in fractures and solution openings. Not an important water-bearer. |
| Codell sandstone member (Carlile shale) |
260 +/- |
Dark gray to black noncalcareous sandy shale and shaly sandstone. Encountered in test holes 1, 3, and 4. |
Two wells (1 and 8) obtain meager supplies of water from the Codell in Finney County. In most places adequate supplies of water may be obtained from higher formations. |
| Blue hill shale member (Carlile shale) |
Dark gray, bluish-black, and black noncalcareous shale containing thin seams of gypsum and in the upper part a zone of septarian concretions. Exposed in wide strip along the Pawnee valley in northeastern Finney County. |
Three unused wells (46, 47, and 57) tap the Blue Hill shale member. Because of the low permeability of the material the wells were abandoned. |
| Fairport chalky shale member (Carlile shale) |
Calcareous shale containing thin beds of chalk or chalky limestone and few thin beds of bentonite. Not exposed in Finney and Gray counties. |
Not known to yield water to wells. |
| Greenhorn limestone |
130 |
Light to dark gray, thin, chalky and crystalline limestones separated by thicker beds of light to dark gray chalky shale that contain thin beds of bentonite. Exposed in small area in southeastern Gray County. |
Reported to yield small supplies of water to wells in southeastern Gray County. |
| Graneros shale |
50 +/- |
Gray noncalcareous shale containing interbedded lenses of sandstone and sandy shale. Not exposed in Finney and Gray counties. |
Relatively impermeable. Not known to yield water to wells. |
| Dakota formation |
50-200 (?) |
Light gray, tan, buff, red, and brown fine- to medium-grained sandstone and light gray, yellow-tan, and brown shale, sandy shale, and clay. Not exposed in Finney and Gray Counties. |
Sandstones yield moderate supplies of soft water to a few wells in southeastern Gray County. |
| ?? |
|
| Comanchean* |
Kiowa (?) shale |
44-100+ |
Gray, bluish-black, black, and yellowish-gray shale containing a few thin beds of gray limestone and sandstone. Not exposed in Finney and Gray counties. |
Relatively impermeable. Not known to yield water to wells in Finney and Gray counties. |
| Cheyenne (?) sandstone |
70 +/- |
Cross-bedded, fine- to coarse-grained, light gray to yellow quartz sandstone, containing interbedded gray to black silty and sandy shale. Not exposed in Finney and Gray counties. |
Not known to yield water to wells in Finney and Gray counties. |
| |
Unconformity |
* - Classification of the State Geological Survey of Kansas.
