Summary of Stratigraphy
The classification and nomenclature of the rock units described in this report have been adopted by the State Geological Survey of Kansas. They differ somewhat from the usage adopted by the U.S. Geological Survey.
The rocks that crop out in Sumner County are sedimentary in origin and range in age from Paleozoic to Recent (Pl. 1). The oldest rocks are a part of the Wellington Formation of the Leonardian Stage, Permian System. The Wellington Formation forms the bedrock surface in approximately the eastern two-thirds of the county and crops out in local areas where it is not covered by Pleistocene deposits. The Ninnescah Shale, also of the Leonardian Stage, forms the bedrock surface in approximately the western third of the county and crops out in local areas where it is not covered by Pleistocene deposits.
Cenozoic deposits of the Pleistocene Series representing four glacial stages and possibly the interglacial stages occur in Sumner County. Deposits of Nebraskan-Aftonian age underlie the surface in the northwestern part of the county near Conway Springs. Deposits of Kansan-Yarmouthian age are most extensive in the eastern and southern parts of the county. Illinoisan-Sangamonian and Wisconsinan terrace deposits border most of the major streams of the county, and Recent deposits form the flood plains and occur also as sand dunes. Deposits of the interglacial stages were not recognized, however, and therefore in this report the deposits referred to a glacial stage include those of the subsequent interglacial stage if present. Deposits of Kansan and Illinoisan age are mapped together on Plate 1.
A generalized section of the rocks that crop out in Sumner County is given in Table 3.
Table 3--Generalized section of rocks* that crop out in Sumner County and their water-bearing characteristics.
|System||Series||Subseries||Stage||Stratigraphic unit||Thickness, feet||Physical character||Water supply, Sumner County|
|Quaternary||Pleistocene||Upper Pleistocene||Recent||Dune sand||0-30||Sand, medium and fine, some silt||Generally above the water table, and does not yield water to wells|
|Alluvium||0-75||Chiefly arkosic sand and gravel; contains discontinuous lenses of silt and clay||Yields large quantities of water to wells|
|Colluvium Recent to Illinoisan||0-25||Silt and clay, minor amounts of sand and gravel, resembling the underlying bedrock material||Does not yield appreciable quantities of water to wells|
|Terrace deposits||0-75||Chiefly arkosic sand and gravel; contain discontinuous lenses of silt and clay. Can be differentiated from alluvium only by topographic position||Yield large quantities of water to wells|
|Illinoisan||Crete Formation||0-65||Poorly sorted sand and gravel; contains considerable red-brown silt and locally derived limestone and shale fragments||Yields moderate quantities of water to wells|
|Lower Pleistocene||Kansan||---||0-90||Poorly sorted sand and gravel; locally contains much silt and clay||Yields moderate quantities of water to wells|
|Nebraskan||Terrace deposits||0-90||Chiefly medium to coarse sand; contain some silt and clay||Yield moderate quantities of water of good quality to wells|
|Permian||Middle Permian||---||Leonardian (Sumner Group)||Ninnescah Shale||0-250||Predominantly silty shale, mostly brownish red with gray-green spots; contains beds of dolomite, calcareous siltstone, and fine-grained sandstone||Yields small quantities of hard water to wells|
|Wellington Formation||40-650||Chiefly shale and silty shale, mostly gray and green, some red; contains lenticular beds of gypsum, silty limestone, dolomite, and the thick Hutchinson Salt member near base||Yields small quantities of hard water to wells|
* The classification is that of the State Geological Survey of Kansan
Kansas Geological Survey, Geology
Placed on web January 2003; originally published August 1961.
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