Pennsylvanian strata in the northeastern Kansas area studied consist of upper Missourian rocks belonging to the Lansing and Pedee groups and lower Virgilian units assigned to the Douglas group (Table 1). The Douglas group is separated from beds of the underlying Missourian Series by a widespread disconformity. Detailed studies were confined to the Tonganoxie sandstone, the basal member of the Stranger formation of the Douglas group. Except for the Tonganoxie sandstone, the following summary is compiled from Moore (1949). Minor changes which apply to the area under discussion have been made.
Table 1. Sequence of upper Pennsylvanian rocks in eastern Kansas.
|South Bend limestone1|
|Rock Lake shale1|
|Captain Creek limestone|
|1Locally absent as result of post-Missourian pre-Virgilian erosion.|
Various strata of the Lansing and Pedee groups of the Missourian Series underlie the Tonganoxie sandstone throughout the area. Knowledge of these strata is necessary in order to understand their relationship to Tonganoxie deposition. The stratigrpahic units are discussed in ascending order.
Captain Creek limestone member--The Captain Creek limestone is the oldest unit cut by the erosion surface on which the Tonganoxie sandstone rests. The Captain Creek limestone is composed of gray to dark-gray massive and evenly bedded limestone. The individual beds are more than 8 inches thick. In most exposures, the limestone has prominent vertical joints. Enteletes pugnoides Newell is abundant in northeastern Kansas and a robust fusulinid, Triticites neglectus Newell, occurs commonly on the bedding planes. Along Kansas River, the member ranges, from 4.5 to 5.5 feet in thickness.
Eudora shale member--The Captain Creek limestone is overlain by the Eudora shale. The lower part is black and fissile, but the upper part is light gray or greenish gray in most places. This black shale is an excellent stratigraphic marker. Megascopic fossils are rare in the Eudora shale of northeastern Kansas. The Eudora shale averages 6 feet in thickness.
Stoner limestone member--This limestone overlies the Eudora shale and is light bluish gray to nearly white; it weathers very light gray or creamy white. Beds of the Stoner limestone weather into thin wavy layers with thin shale partings, although on freshly quarried surfaces it has an appearance somewhat like that of the Captain Creek limestone. To the north it contains abundant Triticites of the T. irregularis type. In uneroded sections this member is 11 to 15 feet thick.
Rock Lake shale member--This shale overlies the Stoner limestone. The lower part is gray to greenish-gray clay shale, but in places it contains very thin silty calcareous partings. Some beds display prominent ripple marks. The upper Rock Lake shale is very sandy in places and locally grades into cross-bedded siltstone or sandstone. Marine fossils distinguish this sandy phase from the Tonganoxie sandstone in places where pre-Tonganoxie erosion has removed the South Bend limestone. Locally, this member contains remains of land plants, reptile bones, fish, and marine invertebrates. The thickness ranges from 5 to 10 feet.
South Bend limestone member--The South Bend limestone is the uppermost member of the Stanton limestone. It lies conformably upon the Rock Lake shale and conformably beneath the Weston shale. It is a dark-gray to blue fine-grained limestone which occurs in beds more than 3 inches thick. The brachiopod Meekella striatocostata (Cox) and a fusulinid similar to Triticites moorei Dunbar and Condra are the most common fossils. The thickness is 2 to 3 feet.
The Pedee group consists of the Weston shale, below, and the Iatan limestone, above. This group conformably overlies the upper beds of the Lansing group and disconformably underlies beds of the Douglas group. Throughout much of Platte County, Missouri, and in the Kansas River Valley, the disconformity cuts out the Pedee group and extends downward into the Stanton limestone. Iatan limestone is present only locally to the north and south of these areas. Lower Douglas beds occupy the stratigraphic position of the Weston shale and Iatan limestone where the latter are missing.
The Weston shale includes strata between the top of the Stanton limestone and base of the Iatan limestone. Where the Iatan is missing, the top of the Weston shale is in contact with lower beds of the Douglas group.
The Weston deposits consist mostly of rather uniform dark-blue to bluish-gray marine shale containing several zones of sub-cylindrical ironstone concretions which lie parallel to the bedding planes. The thickness of the Weston shale is about 55 feet at Beverly Junction, Missouri, and about 70 feet at Vinland, Kansas. Post-Missourian erosion has removed most of the Weston shale in the intervening area.
The Iatan limestone overlies the Weston shale conformably and is overlain disconformably by basal deposits of the Douglas group. In the vicinity of Leavenworth, the limestone is light bluish gray to white, both on fresh and weathered surfaces. The bedding is somewhat uneven and indistinct, imparting a massive appearance, Brachiopods, bryozoans, and crinoid fragments are the most common fossils.
Northeast of Vinland, in Douglas County, it seems that prolonged exposure during early Virgilian time greatly altered the appearance of the Iatan limestone. Here the Iatan is 0.5 to 3 feet thick and is weathered blue gray, light brown, or brown to reddish brown. Incrustations, dense nodules, and thin platy beds, separated by what seems to be residual material, are evidence of solution and downward movement of calcium carbonate which has been redeposited at lower levels. The appearance of the Iatan points to development of a soil during part of early Virgilian time, prior to deposition of the overlying beds.
The rocks of the Douglas group are divided into two formations: the Stranger (lower) and the Lawrence (upper).
The Stranger formation consists of nonmarine and marine beds of the lower part of the Douglas group, extending upward to the disconformity at the base of the Lawrence formation. In north-eastern Kansas, the top of the Haskell is defined as the upper boundary of the Stranger formation, because the Robbins shale member (uppermost Stranger of some areas) commonly is absent or cannot be identified there.
Tonganoxie sandstone member--The Tonganoxie sandstone includes all strata from the disconformity at the base of the Stranger formation upward to the top of the Upper Sibley coal or the base of the Westphalia limestone member. It consists of a thin basal conglomerate, a sandstone, a shale, and at the top, a coal (Upper Sibley coal). Since the character and origin of the Tonganoxie member are the subject of this paper, this part of the Stranger formation will be discussed in detail subsequently. The Tonganoxie member ranges in thickness from 4 to 100 feet in the northeastern Kansas area.
Westphalia limestone member--In northeastern Kansas, a carbonaceous laminated dark-blue limestone has been identified tentatively as equivalent to the Westphalia limestone of southern Kansas. This dark-blue limestone is widespread throughout the area, occurring 3 to 4 inches above the top of the Upper Sibley coal. A calcareous zone marks its position where the limestone is not well developed. The limestone contains abundant small gastropods and ostracodes in northern Leavenworth County. Ostracodes are the only invertebrate fossils found in this bed in Douglas County, but plant remains are common almost everywhere.
The Westphalia limestone of southern Kansas is characterized by the presence of abundant fusulinids. Faunally and lithologically, the dark-blue limestone occurring persistently next above the Tonganoxie sandstone in northeastern Kansas seems to be a brackish water deposit. Because it occupies the same stratigraphic position as the type Westphalia limestone, the dark-blue limestone is reasonably interpreted as the near-shore equivalent of the off-shore fusulinid-bearing Westphalia limestone of southern areas. The gastropods found in the presumed Westphalia of Leavenworth and adjacent counties may be fresh-water forms. In the areas where the Upper Sibley coal is poorly developed, the bed identified as Westphalia limestone makes an excellent stratigraphic marker for defining the top of the Tonganoxie sandstone member. The Westphalia in northeastern Kansas ranges from 0.3 to 1 foot in thickness.
Vinland shale member--This shale conformably, and in some places disconformably, overlies the Upper Sibley coal and the Westphalia limestone. It contains variable thicknesses of clayey to sandy shale and sandstone. Except locally, the Vinland deposits are entirely marine. The shale is blue gray and light brown. The sandstone and siltstone beds are light brown to brown. Near the town of Tonganoxie, along U. S. Highway 40 (SE cor. sec. 2, T. 11 S., R. 21 E.), and 2.5 miles south of Lawrence (Cen. E. line sec. 25, T. 13 S., R. 19 E.), the Vinland contains silty and massive sandstones up to 12 feet thick, which occur in the top part of the member. In other places where these silts and sandstones occur at the base of the Vinland shale, the underlying Upper Sibley coal and Westphalia limestone commonly are missing. Excellent plant fossils, but no invertebrates, were found in the lower sandstone zones. The upper sandstone and shale grade into the overlying marine Haskell limestone. The thickness of the Vinland shale in northeastern Kansas ranges from 7 to 25 feet.
Haskell limestone member--The Haskell member is a very persistent limestone which lies conformably on the Vinland shale member. The lower beds of the Haskell are sandy and contain abundant pelecypods. In northeastern Kansas, there are local thin coquinoidal beds composed of fragments of brachiopods, pelecypods, and crinoids. At some places fusulinids are abundant. The main part of the Haskell is a bluish-gray blocky fine-grained limestone. The Haskell is 2 to 4 feet thick at most outcrops.
Robbins shale member--Throughout most of Leavenworth and Douglas Counties, the Ireland sandstone rests directly on the Haskell limestone or on older strata, but south of Lawrence, near Baldwin, the Ireland sandstone rests on the Robbins shale. Here, the Robbins shale is a gray argillaceous silty shale which contains a zone of ellipsoidal phosphatic concretions at the base. These concretions contain ammonoid cephalopods and fish brain casts. Near Baldwin, the Robbins shale is 1 to 5 feet thick, but southward it thickens to 100 feet,
The Lawrence formation includes strata from the top of the Haskell limestone to the base of the Oread formation. The disconformity at the base of the Ireland sandstone member marks the lower boundary of the Lawrence formation. Where the Robbins shale is absent or not recognized, and the Ireland seemingly rests conformably upon the Haskell limestone, the top of the Haskell limestone is designated as the base of the Lawrence formation.
Ireland sandstone member--The disconformity at the base of the Ireland sandstone locally cuts through the Robbins shale, Haskell limestone, and Vinland shale into the Tonganoxie sandstone. Where the latter is thin, the disconformity at the base of the Ireland may cut through the Tonganoxie into the Weston shale or the Stanton limestone. The Ireland sandstone is light to reddish brown, typically containing disseminated iron compounds, which impart a speckled appearance upon weathering. The sandstones are thin-bedded to massive and in places cross-bedded. Where the Ireland rests on deeply eroded Haskell limestone, the sand is cemented by calcium carbonate. Heavy minerals are common throughout the Ireland sandstone. The thickness of the Ireland sandstone ranges from 3 to 80 feet in northeastern Kansas.
Amazonia limestone member--This limestone, which is found elsewhere in the upper part of the Lawrence formation, is not recognized in the Leavenworth and Douglas County area.
Kansas Geological Survey, Geology
Placed on web Aug. 7, 2006; originally published Oct. 31, 1950.
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