Following is a brief discussion of the rock sequence that embraces the beds of the Marmaton group. Table 1 shows the classification of the Pennsylvanian rocks in the northern Mid-Continent region. Table 2 gives the classification of the Marmaton group.
Table 1--Classification of Pennsylvanian rocks in the northern Mid-Continent region
|(unconformity indicated by local channeling)|
|Kansas City group|
|*The lowermost few feet of the Cherokee shale in Kansas probably should be assigned to the Lampasan series.|
Table 2--Classification of rocks of the Marmaton group.
|Idenbro limestone member|
|Perry Farm shale member|
|Norfleet limestone member|
|Includes Walter Johnson sandstone|
|Worland limestone member|
|Lake Neosho shale member|
|Tina limestone member|
|Includes Bandera Quarry sandstone and Mulberry coal|
|Laberdie limestone member|
|Mine Creek shale member|
|Myrick Station limestone member|
|Anna shale member*|
|Includes Warrensburg? sandstone (Englevale sandstone)|
|Fort Scott limestone|
|Higginsville limestone member|
|Little Osage shale member|
|Includes Houx limestone and Summit coal|
|Blackjack Creek limestone member|
|*In Kansas a very thin limestone is included in the Anna shale at its base. In neighboring parts of Missouri and Oklahoma, thicker limestone in the same position clearly belongs to the Pawnee formation.|
Disconformity at the Base of Pennsylvanian Rocks
In the northern Mid-Continent area, where these studies are chiefly centered, Pennsylvanian rocks lie upon an eroded surface of other rocks ranging in age from pre-Paleozoic to Late Mississippian. In most.of the area Pennsylvanian sediments rest upon various formations of the Mississippian system. Locally, as in the Central Kansas uplift and in the Nemaha uplift, Pennsylvanian beds overlap and overstep older rocks, including those of pre-Paleozoic age. Structural conditions in Mississippian and older rocks indicate an important time break between the Pennsylvanian and Mississippian systems.
The oldest Pennsylvanian rocks, those of Morrowan age, are separated from the overlying Pennsylvanian beds by a structural disconformity in southeastern Oklahoma. Rocks of Lampasan age lie above this disconformity and the Lampasan rocks are overlain by those of Desmoinesian age.
Pennsylvanian Rocks Older than the Desmoinesian
In the deeper basins, nearer to and in the Appalachian trough (Pennsylvania to Texas), there are Pennsylvanian rocks older than those assigned to the Desmoinesian series. These are the rocks of Morrowan and Lampasan (or Derryan) age. In general, sediments that are assigned to the Lampasan series extend farther west and north from the Appalachian geosyncline than do those of Morrowan age. Rocks of Morrowan age, wherever known, are separated from younger sediments by a structural disconformity, and paleontologic evidence indicates a hiatus between sediments assigned to the Lampasan series and the Desmoinesian series.
In the Mid-Continent region, rocks assigned to the Desmoinesian series include beds above the McAlester formation in central Oklahoma and in the Arkansas river valley; above the Pumpkin Creek beds in the Ardmore basin, Oklahoma; above the Smithwick group in north-central Texas; and below a widespread disconformity that occurs at the base of the Bourbon rocks in Kansas and at the base of the Seminole formation in Oklahoma (Moore and others, 1944., pl. 1, chart 6). In some previous publications the base of the Atoka formation has been designated as the base of the series (Moore, 1936, p. 53). Now, however, the Atoka beds and overlying sediments, including the Hartshorne sandstone and the McAlester shale, are assigned to the Lampasan series (Moore and others, 1944, pl. 1).
In Kansas the Marmaton group and the underlying Cherokee shale commonly are assigned to the Desmoinesian series (Moore, 1932; 1936, p. 51), but from studies in eastern Oklahoma Newell (1937, p. 39) has shown evidence that the Warner sandstone in the McAlester formation is the equivalent of the basal part of the Cherokee shale in southeastern Kansas. If this is true, the base of Desmoinesian rocks, as now defined, occurs a few feet above the base of the Cherokee shale in its type area.
The disconformity at the top of Desmoinesian rocks has been traced for great distances (Jewett, 1941, p. 298). In Oklahoma the disconformity at the top of the series is at the base of the Seminole formation (Moore, 1936, p. 53; Oakes and Jewett, 1943). In Kansas the disconformity occurs at the base of the Hepler sandstone which is the basal part of the Bourbon deposits and is correlated with the upper part of the Seminole formation. That is, Missourian rocks overlap Desmoinesian strata from the south or rocks lying on the disconformable surface in Kansas are slightly younger than those that lie on the same surface farther south. The Chariton conglomerate in Iowa is believed to be the northward extension of the Hepler sandstone and to be of about the same age.
The type section of Desmoinesian rocks is along Des Moines river in central Iowa, but it seems that the lower part of the Des Moines river section, the "lower Cherokee," should be assigned to the Lampasan series.
It should be noted that the term Desmoinesian is now restricted to include only the upper part of the rock-time unit that commonly has been called the Desmoinesian series. Moore (Moore and others, 1944, pp. 671, 673, 675-677) has presented criteria for the separation of another series, the Lampasan to which older post-Morrowan rocks are assigned. Hence, the Desmoinesian rocks comprise a unit that is third from the base of the Pennsylvanian system. The older series are the Morrowan and the Lampasan.
Sediments of Lampasan and Desmoinesian age were deposited in the Appalachian trough from Pennsylvania to New Mexico. This area was seemingly a part of a great depression west and north of a positive segment that is designated as Appalachia-Llanoria. The border of this old land area probably traced a line that crossed eastern Pennsylvania, western Virginia, eastern Tennessee, northwestern Georgia, central Alabama, central Mississippi, southern Arkansas, and Texas to about the middle point of the Texas-Mexico boundary. Deposition of Pennsylvanian sediments is believed to have taken place in the form of transgressive overlap away from the eastern and southern positive area, Appalachia-Llanoria. By the close of Desmoinesian time and probably earlier, transgression was met by similar transgression from other directions and from other positive areas that were being eroded. Diastrophic movements within the basins were of differential nature. The presence of many local hiatuses and the occurrences of overlap are probable.
The Cherokee shale is defined to include strata from the base of the Pennsylvanian north of the Kansas-Oklahoma line upward to the base of the Fort Scott limestone (Moore, 1936, p. 55). This definition is the same as the original definition of Haworth and Kirk (1894, p. 105).
In writing of Pennsylvanian rocks in eastern Oklahoma, numerous geologists have used the term Cherokee to include strata above the disconformity at the top of rocks of Morrowan age and below the Fort Scott limestone. As explained elsewhere in this paper, it is evident that some of the post-Morrowan beds in eastern Oklahoma are older than the oldest strata included in the type Cherokee section in southeastern Kansas. It is well established that the Lampasan rocks overlap older rocks northward from the deeper basins of southeastern Oklahoma and that the basal sediments in southeastern Kansas are equivalent in age to rocks well above the base of the post-Morrowan Pennsylvanian section in eastern Oklahoma.
Cherokee rocks are chiefly clastic. Shale is strongly predominant. Gray clayey and silty micaceous shale is most common but there is also much sandy shale and sandstone. Very dark or black carbonaceous shale occurs at several horizons. Fifteen coal beds have been identified in the Kansas Cherokee section. The amount of limestone is very minor. Sandstones in the Cherokee rocks commonly occur in lenticular bodies but the lenses are arranged in definite stratigraphic zones. "Shoestring sands," long narrow channel fillings or bar deposits, are numerous and many of them are important oil and gas reservoirs.
The maximum known thickness of Cherokee rocks north of Oklahoma is in the Forest City basin in northeastern Kansas and in northwestern Missouri. The thickness there slightly exceeds 700 feet. The average thickness in southeastern Kansas is about 400 feet. The thickest section in southeastern Kansas is in Labette County where about 500 feet has been measured. On the low structural arch between the Forest City basin and the Cherokee basin the thickness is about 350 feet. Rocks of the Cherokee group overlap older beds on the Ozark uplift giving rise to a much smaller thickness of Cherokee rocks in several Missouri counties.
Cherokee rocks are generally absent or are very thin in Kansas west of the Nemaha ridge. However, basal Pennsylvanian rocks in the Sedgwick basin in south-central Kansas and a part of the "Sooy" conglomerate in much of western Kansas are believed to be equivalent to the upper part of the Cherokee shale of eastern Kansas.
Whether or not the Cherokee rocks in eastern Kansas and neighboring places are dominantly marine is a debatable question. Limestones and other rocks containing marine fossils are rare. Fossil land plants are plentiful. All detailed descriptions of Cherokee deposits in southern Iowa, western, and northern Missouri, eastern Kansas, and eastern Oklahoma indicate that they were laid down under cyclical conditions. Abernathy (1937a, p. 19) identified 15 successive cyclic deposits in the type locality. A characteristic cyclothem includes in ascending order: (1) sandstone, (2) sandy shale, (3) underclay, (4) coal, (5) black shale, (6) gray shale, (7) limestone, and (8) calcareous shale.
The Ardmore limestone, about 100 feet below the top of the Cherokee shale, is the most prominent limestone in the Kansas and Missouri Cherokee section. It has been correlated by several geologists with the Verdigris limestone of eastern Oklahoma. Abernathy (1937a) stated that the Ardmore limestone lies in the second cyclothem below the Fort Scott cyclothem, but observations in the type locality of the Verdigris limestone indicate that it is separated from the Fort Scott limestone by several cyclical units.
Certain notations concerning the nature of the probable northward overlap of Pennsylvanian rocks should be made here. (1) Although geologists are not in accord with the theory that such overlap occurs, northward overlap of these basal rocks is fairly evident. (2) Studies sufficient to show evidence of continuously progressive overlap have not been made. (3) Observations indicate, on the other hand, that now and then regressive overlap or offlap took place. That is, each successively younger deposit does not extend farther to the north than do all the preceding ones. If one assumes that generally the strata overlap northward but that now and then, in the course of their deposition, some sedimentary units were not as far-reaching as others, one can then account for the discrepancy in the number of cyclical units between the Verdigris limestone (Ardmore) and the Fort Scott limestone in the two places.
The Marmaton is the upper of two rock units in Kansas recognized as being of Desmoinesian age. The lower unit is the Cherokee shale. In 1932 and 1936 Moore (1936, p. 57) defined the Marmaton group as including beds between the base of the Fort Scott limestone and the upper limit of the Desmoinesian series. The disconformity at the base of the Hepler sandstone seems to be the upper limit of the Desmoinesian series in Kansas. This pre-Missourian disconformity and overlying sandstone and conglomerate are rather definitely identified from southern Oklahoma to Iowa, Illinois, and Indiana (Oakes and Jewett, 1943; Jewett, 1940a, pp. 8, 9; Jewett, 1941, pp. 299, 300; Weller, Wanless, Cline, and Stookey, 1942, p. 1592). The Marmaton group is set apart from the underlying Cherokee shale because the former is more dominantly calcareous. It includes four limestone formations and four shale formations. These formations are identified along their line of outcrop from Arkansas river valley in Oklahoma to Iowa and Illinois.
The Marmaton group comprises, in ascending order (1) Fort Scott limestone, (2) Labette shale, (3) Pawnee limestone, (4) Bandera shale, (5) Altamont limestone, (6) Nowata shale, (7) Lenapah limestone, and (8) Memorial shale. The combined thickness in Kansas is about 250 feet. The type locality of the Marmaton group is along Marmaton river, from Uniontown to Fort Scott, Bourbon County, Kansas. All beds can be seen along the river bluff between the two places and most of them are exposed along U.S. highway 54 between Uniontown and Fort Scott.
Disconformity Between Desmoinesian and Missourian Rocks
A widespread and important disconformity occurs between rocks assigned to the Desmoinesian series and those assigned to the Missourian series. This is indicated by biologic evidence as well as by evidence of a physical break. For a number of years it has been known that an important faunal and floral break occurs somewhere within the section that had commonly been assigned to the Pleasanton formation (Memorial shale and Bourbon shale). More recently it has been shown that in Kansas and eastern Missouri there is an erosional disconformity at the base of the Bourbon shale and that a thin sandstone in that zone rests upon an eroded surface that ranges from a position almost as low as the top of the Altamont limestone (and, in the shallow subsurface, locally lower) to 30 or more feet above the Lenapah limestone (Jewett, 1941, p. 299). Recent studies indicate, also, that rocks of Missourian age were deposited with structural overlap from the south on Desmoinesian beds (Jewett, 1941, p. 300; Oakes and Jewett, 1943). Evidence indicating that the pre-Missourian disconformity can be traced across Missouri into Iowa and is present in Illinois is accumulating. The Chariton conglomerate in Iowa seems to be equivalent to the basal Missourian sandstone of eastern Kansas and western Missouri (Weller, Wanless, Cline, and Stookey, 1942, p. 1592).
Kansas Geological Survey, Geology
Placed on web Feb. 2, 2010; originally published April 1945.
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