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Paleozoic Era
By Edwin D. Goebel
Marine and nonmarine sedimentary rocks of Paleozoic age underlie all of Kansas. All the systems of the Paleozoic Era are recognized (Pl. 1). In the eastern part of the State, upper Paleozoic rocks that are chiefly Permian and Pennsylvanian in age crop out. Some Mississippian rocks are exposed in Cherokee County in extreme southeastern Kansas. Many of the series in the Paleozoic are absent or only partially developed in Kansas. Exposed Mississippian, Pennsylvanian, and Permian rocks have been intensively studied by many investigators, but work by Raymond C. Moore is noteworthy and has made the outcropping Pennsylvanian rocks in Kansas and surrounding areas internationally known. Sedimentary strata consisting of shale, limestone, dolomite, sandstone, conglomerate, breccia, and chert make up the bulk of the Paleozoic section. Coal, salt, gypsum, and other rock types occur in certain beds.
The total thickness of exposed Paleozoic rocks in Kansas, derived by compiling average measurements of subdivisions, is approximately 6,100 feet. The aggregate thickness of outcropping and subsurface Paleozoic rocks exceeds 11,500 feet. Paleozoic rocks are unconformable on the Precambrian and have an unconformable relationship with Mesozoic or Cenozoic rocks. Within the Paleozoic, major unconformities separate Pennsylvanian (Desmoinesian) from Mississippian rocks and Mississippian-Devonian rocks (Chattanooga Shale) from older Paleozoic rocks. Mississippian and older Paleozoic rocks are preserved for the most part in structural and stratigraphic basins. In Figure 2 pre-Chattanooga structural provinces are depicted, and in Figure 6 late Mississippian and early Pennsylvanian structural provinces are depicted.
Figure 2--Generalized pre-Devonian-Mississippian (pre-Chattanooga Shale) structural features in Kansas (adapted from Moore and Jewett, 1942).
All pre-Pennsylvanian formations were involved in the structural movements that deformed Pennsylvanian and younger rocks. The pre-Pennsylvanian, and especially the pre-Mississippian rocks, had already sustained structural deformations at variance with the later movements, and this resulted in some areas of marked discordance between the regional structure at the surface and that in the subsurface. Faults having small displacements are observed in a few places, but nowhere in Kansas is faulting in surface rocks a conspicuous feature.
The names of some rock units exposed in Iowa, Illinois, Missouri, Arkansas, and Oklahoma have been given to the Kansas subsurface rock units thought to be lateral equivalents. As with outcropping Paleozoic rocks, many Kansas subsurface units probably are time-transgressive. Some were deposited in this area earlier or later than their exposed counterparts.
CAMBRIAN SYSTEM
By Edwin D. Goebel
No rocks of Early or Middle Cambrian age have been reported in boreholes in the Midcontinent area (Skillman, 1948). Upper Cambrian rocks are recognized in Kansas, and their distribution is similar to the distribution of rocks of Early and Middle Ordovician age. The combined thickness of Upper Cambrian sediments is approximately 475 feet.
Cambrian rocks in Kansas comprise a marine sedimentary sequence of arkosic sandstone beds overlain by beds of dolomite. Upper Cambrian rocks unconformably overlie Precambrian rocks and conformably underlie rocks of Ordovician age.
Upper Cambrian Series
Three Upper Cambrian formations that crop out in Missouri have been correlated with subsurface units in Kansas. The oldest of these, the Lamotte Sandstone, is equivalent in position to the Reagan Sandstone of Oklahoma. The Bonneterre Dolomite is equivalent to the Honey Creek Limestone of Oklahoma. The youngest, the Eminence Dolomite, is included in the Arbuckle Group.
LAMOTTE SANDSTONE
The Lamotte is a basal Paleozoic sandstone. The sand grains composing the Lamotte are poorly sorted, rounded to angular, and coarse to fine. Quartzose sandstone, dolomitic sandstone, quartz-glauconite sandstone, arkose, and feldspathic sandstone are the dominant rock types. Arkosic material occurs in the lower part adjacent to Precambrian rocks. The Lamotte Sandstone was deposited unconformably on a complex of Precambrian rocks that formed an uneven surface of low relief. The formation is widespread in Kansas beneath the Bonneterre, but locally the Lamotte is absent and the Bonneterre lies on the Precambrian. Absence of the Lamotte locally in the area of the Central Kansas uplift and the Cambridge arch is attributed to post-depositional erosion. Thicknesses of 80 to 130 feet have been reported in southeastern Kansas, and as much as 175 feet in western Kansas, but the average thickness is about 40 feet.
BONNETERRE DOLOMITE
The Bonneterre is a conspicuously glauconitic, noncherty dolomite which is dark gray to brown and finely crystalline in eastern Kansas and buff to white and coarsely crystalline in western Kansas. It includes sandy and silty dolomite, and, locally near the top, dolomitic shale beds. The Bonneterre is distributed throughout Kansas except in places on the Central Kansas uplift and the Nemaha anticline. In western Kansas, most of the rocks reported to be Arbuckle are probably equivalent to the Bonneterre (Merriam, 1963). The Bonneterre is gradational downward into the Lamotte Sandstone. The thickness ranges from 0 at the margins of some uplifts to 150 feet in basin areas.
Undifferentiated Upper Cambrian and Lower Ordovician
Undifferentiated subsurface Cambrian and Ordovician rocks consist mostly of dolomite with lesser amounts of limestone, sandstone, and shale. They are absent from higher parts of the Nemaha anticline, Central Kansas uplift, and Cambridge arch (Fig. 6).
Arbuckle Group
The Arbuckle Group consists of Upper Cambrian and Lower Ordovician deposits, its subdivisions in Kansas being units that crop out in Missouri. The group includes the Eminence Dolomite, Gasconade Dolomite, Roubidoux Formation, Jefferson City Dolomite, and Cotter Dolomite. The Eminence is Late Cambrian in age; the other formations are Early Ordovician in age. "Arbuckle" sometimes is used for all rocks between the top of the Lamotte Sandstone and the base of the Simpson Group. Some authors restrict the term "Arbuckle" to rocks of Ordovician age.
The Arbuckle Group (Merriam, 1963) consists mainly of white, buff, light-gray, cream, and brown crystalline dolomite. Chert is common in the upper part. The aggregate thickness exceeds 1,200 feet. Where the Lamotte Sandstone is absent, the Bonneterre Dolomite and Arbuckle rocks commonly overlie the Precambrian. The Arbuckle Group thickens toward Oklahoma and Missouri.
EMINENCE DOLOMITE
Cherty, buff to white, very coarsely crystalline dolomite makes up the Eminence. Vitreous semitranslucent chert contains cavities encrusted by finely crystalline quartz. The chert commonly is mixed so intimately with the dolomite that insoluble residues consist dominantly of chert with lacelike, interconnecting molds of dolomite crystals. An angular unconformity separates the Eminence from the Bonneterre. Occurrence of Eminence deposits in eastern Kansas is confined mostly to a belt three counties wide bordering Missouri. It is recognized also in parts of western Kansas. The formation thickens eastward from 0 to more than 150 feet at the Missouri state line. Thicknesses of 40 to 90 feet are reported in west-central Kansas.
GASCONADE DOLOMITE
Moore, Frye, Jewett, Lee, and O'Connor (1951) treated the Gasconade Dolomite and underlying Van Buren Formation as a unit (p. 119). Earlier, McQueen (1931, p. 18) differentiated the formations in Missouri by means of insoluble residues. Because the formations are difficult to separate in the subsurface far removed from outcrops, Keroher and Kirby (1948) designated the sequence in Kansas as Van Buren-Gasconade. The Missouri Geological Survey (Martin, Knight, and Hayes, 1961) no longer recognizes the Van Buren and includes the rock sequence from the top of the Eminence Dolomite to the base of the Roubidoux Formation as the Gasconade Dolomite. This practice is now followed in Kansas also.
The Gasconade consists mainly of cherty, coarsely granular dolomite. The chert in the upper part, which is dense and gray to dark bluish-gray, grades downward into white, dense, quartzose chert. The Gasconade is unconformable on Eminence beds and probably also on Bonneterre, Lamotte, and Precambrian beds. Gasconade rocks are reported in the subsurface in a belt along the Missouri state line. The thickness ranges from 0 to more than 200 feet in southeastern Kansas.
Gunter Sandstone Member
This member, present at the base of the Gasconade, is a sandy dolomite.
ROUBIDOUX FORMATION
In Kansas, this formation consists mainly of sandy dolomite and fine-grained sandstone. Deposition of the Roubidoux seems to have been preceded by folding and erosion of older rocks. Thickness of the formation generally ranges from 150 to 200 feet.
JEFFERSON CITY DOLOMITE and COTTER DOLOMITE
Because the Cotter Dolomite and Jefferson City Dolomite recognized in outcrops are not distinctly separable in the subsurface on lithologic criteria, they are treated as a unit. They consist mainly of coarsely granular, cherty dolomite. The upper part of the sequence includes much oolitic chert which becomes white and decreases in volume toward the base where white, tripolitic chert becomes abundant. These rocks unconformably underlie different formations, such as the St. Peter Sandstone on the flank of the Southeast Nebraska arch, the Chattanooga Shale on the Chautauqua arch, and Pennsylvanian rocks on parts of the Central Kansas uplift and Nemaha anticline. The Jefferson City Dolomite probably is conformable on the Roubidoux Formation. The Cotter-Jefferson City sequence ranges in thickness from 0 feet in northern Kansas to more than 650 feet in Cowley County in southern Kansas.
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Kansas Geological Survey, Stratigraphic Succession in Kansas
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Web version August 2005. Original publication date Dec. 1968.
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