Stratigraphy of Outcropping Rocks
Pennsylvanian System--Virgillian Series
Douglas GroupStranger Formation
The Stranger Formation is divided into five members designated, in ascending order, the Tonganoxie Sandstone, the Westphalia Limestone, the Vinland Shale, the Haskell Limestone, and the Robbins Shale. The formation rests unconformably on various parts of the Weston Shale and Stanton Limestone. Its maximum thickness is about 160 feet, but locally the Stranger Formation is absent and the Ireland Sandstone member of the Lawrence Shale directly overlies the Weston Shale.
Tonganoxie Sandstone member--The Tonganoxie Sandstone member in this area is believed to be a non-marine sandstone that occupies an erosional river valley cut into the Weston Shale and Stanton Limestone. Lins (1950) described the lithology, origin, and environment of the Tonganoxie Sandstone member in its outcrop area in Douglas, Leavenworth, and Wyandotte Counties. The erosional valley trends southwestward and is 14 to 20 miles wide. The City of Lawrence overlies about the middle of the valley. According to Lins, the Tonganoxie Sandstone member contains four distinct lithologic units, which, in ascending order are conglomerate, sandstone, Shale, and coal. Sanders (1957), in a study of the sandstones of the Douglas and Pedee Groups in northeastern Kansas, concluded that the ancient Tonganoxie Valley of Lins continued in a southwesterly direction from the vicinity of Lawrence for at least 70 miles and had a width of 12 to 20 miles. The general location of the deeper part of the ancient Tonganoxie Valley is shown in Figure 4.
Figure 4.--Generalized map of Douglas County showing location of ancient valley in which Tonganoxie Sandstone member of Stranger Formation was deposited.
The basal conglomerate consists of fragments of concretions derived from the Weston Shale, fragments of limestone derived from the Stanton and Iatan Limestones, reworked invertebrate fossils, plant fragments, quartz sand and silt, and cementing material. The conglomerate is thickest and best developed where the Stranger Formation is in contact with parts of the Stanton Limestone. As would be expected, the conglomerate is not present everywhere, sandstone or sandy shale being the basal deposit locally. In areas of thin Tonganoxie overlying pre-Tonganoxie hills of Weston Shale, the basal deposits of the Tonganoxie may be represented by a thin zone of subrounded to subangular shale and siltstone pebbles. A thin deposit of Tonganoxie Sandstone overlying thick Weston Shale, between which the disconformity can be recognized, is well exposed along the north side of a road cut in the SW1/4 NE1/4 sec. 26, T.14 S., R. 20 E.
The Tonganoxie Sandstone member is chiefly fine to very fine 1/4 to 1/16 mm) angular to subangular clear quartz, which is slightly cemented with calcite. Poorly sorted silty and shaly beds may contain as much as 20 percent of mica by volume. Festooned crossbedded and massive sandstone (PI. 4 B) is present in the lower part of the Tonganoxie Sandstone member at many places. The well-sorted channel-sandstone deposits grade laterally and vertically into thin-bedded argillaceous sandstone, siltstone, and shale, which are more micaceous and carbonaceous than the massive sandstone. The upper and middle parts of the member contain the fairly persistent Upper and Lower Sibley coals and, locally, other thin coals.
On fresh exposures the sandstone is very light gray to dark gray, the darker sand containing more carbonaceous material, the lighter sand being better sorted and cleaner. Small amounts of disseminated pyrite and iron-bearing clay minerals cause the sandstone to become stained with iron and to weather to tan or yellow brown on outcrops. The siltstone and shale beds of the Tonganoxie Sandstone member are gray to blue and weather tan to yellow brown. Ironstone and limonite concretions occur both in zones and scattered through the shaly parts of the member. Where the Westphalia Limestone member can not be recognized, the top of the Tonganoxie Sandstone member is placed at the top of the Upper Sibley coal. The thickness of the Tonganoxie ranges from 0 to about 120 feet.
Westphalia Limestone member--The Westphalia Limestone member is a medium-gray, carbonaceous laminated limestone as much as 1.5 feet thick, but it is not continuous and hence is not present at some of the outcrops of the section of rocks in which it normally occurs. A zone of calcareous shale above the Upper Sibley coal marks its probable position where limestone is not present, however. In addition to the carbonized plant fragments found in the bedding planes, it also contains the ostracode Jonesina howardensis and tiny gastropods. Its position directly over the Upper Sibley coal, its faunal assemblage, and its laminated appearance make this limestone unlike other underlying and overlying limestones and very easy to identify. The bed can be observed at several localities in the drainage area of Coal Creek and is well exposed in a road cut in the NW1/4 NE1/4 sec. 13, T. 14 S., R. 20 E.
Vinland Shale member--Gray clayey to sandy shale and sandstone beds. chiefly marine, ranging from about 6 to 25 feet in thickness, compose the Vinland Shale member. A zone of the pelecypod Myalina persists nearly everywhere in the shale and sandstone at the top of the member. Beds of sandstone in the upper part locally attain a thickness of about 12 feet. The sand is fine to very fine, slightly micaceous, and on outcrops is commonly well cemented with calcite. Beds of calcite-cemented sandstone directly underlying the Haskell Limestone member are exposed in road and creek cuts near the center of the S1/2 sec. 8, T. 14 S., R. 20 E. At a small quarry along the east side of a creek in the NW1/4 NE1/4 sec. 4, T. 15 S., R. 21 E., the equivalent beds are 10 to 15 feet of thin, irregular beds of silty and sandy limestone interbedded with limy sandstone, all of which contain a molluscan fauna. In sec. 34 and 35, T. 14 S., R. 20 E., the Vinland Shale member contains a zone of red and green shale together with a thin coal above the sandstone in the upper part of the member. Most outcrops of the Vinland are gray, tan-weathering, silty to sandy shale. Septarian concretions occur locally in the upper part.
Haskell Limestone member--Overlying the Vinland Shale member is the gray to bluish-gray, fine-grained Haskell Limestone member, which weathers brownish gray. The lower part of the Haskell Limestone member may be silty or very sandy locally where it overlies and is gradational into beds of sandstone in the Vinland Shale member. The lower, sandy part contains abundant mollusks. Fusulinids, brachiopods, crinoids, and calcareous "Cryptozoon"-type algae are common in the upper and middle parts, and locally the upper part is oolitic. The upper surface has numerous depressions containing small phosphatic nodules. The nodules contain a fauna (Twenhofel and Dunbar, 1914) including ganoid fish skulls and brain casts, nautiloids, ammonites, and orbiculoid brachiopods. Miller and Swineford (1957) discussed the paleoecology of the nodulose zone and concluded that the nodules are genetically related to and should be included with the Haskell Limestone rather than the Robbins Shale member.
The Haskell Limestone member is well exposed in and east of the City of Lawrence between Kansas and Wakarusa Rivers, and in the Coal Creek drainage area. It is the most widespread and distinctive marker bed between the Oread and Stanton Limestones in both the subsurface and outcrop areas of the Douglas and Pedee Groups. Its thickness ranges from about 1.3 to 5 feet. In the southern part of Douglas County post-Robbins pre-Ireland erosion locally removed the Haskell Limestone member and older beds.
Robbins Shale member--The Robbins Shale member is a gray marine clayey shale 50 to 100 feet thick in the vicinity of its type locality near Yates Center in Woodson County. In southern Douglas County the Robbins Shale member ranges in thickness from 0 to about 12 feet and is directly overlain by massive beds of the Ireland Sandstone member, which are believed to be of non-marine origin. In the northern two-thirds of the county, the Ireland Sandstone member is not recognized and the sequence from the base of the Oread Limestone to the top of the Haskell Limestone member is chiefly silty and sandy shale. Earlier workers (Patterson, 1933; Moore, 1936, 1949; Lins, 1950; Reynolds, 1957) studying these beds in the vicinity of Lawrence concluded that nearly all the clastic beds between the Oread Limestone and the Haskell Limestone member, except for a few inches of shale directly overlying the Haskell Limestone member, should arbitrarily be included in the Lawrence Shale. This provides a practical solution for mapping also, as the top of the Haskell and the base of the Oread are contacts that can be readily mapped in the field. The top of the Haskell Limestone was mapped throughout Douglas County as the boundary between the Lawrence Shale and the Stranger Formation, and the thin Robbins Shale member in the Baldwin area has been mapped with the Lawrence, Shale. Where pre-Ireland erosion removed the Haskell Limestone the base of the Ireland Sandstone is mapped as the formation boundary.
It is to be noted that Patterson (1933) collected several species of foraminifers, chiefly arenaceous types, ostracodes, and holothurian plates and spicules from the "lower Lawrence" shale beds above the Haskell Limestone member. Detailed stratigraphic and paleontologic studies of the Lawrence-Robbins shale section may reveal the presence of a considerable thickness of the marine or brackish-water Robbins Shale.
The Robbins Shale member exposed in the Baldwin area is a marine gray to blue argillaceous very thin bedded shale that weathers yellow tan. A few inches above the base is an impure goethite bed about 2 or 3 inches thick containing a molluscan fauna. Sparse marine fossils also occur in the lower part of the shale. Miller and Swineford (1957) described in detail the lower part of the Robbins Shale.
The Lawrence Shale includes strata between the Robbins Shale member and the Oread Limestone in the southern third of Douglas County, but in the northern two-thirds, because the contact between the Robbins Shale and Lawrence Shale is indeterminate, all deposits between the Oread Limestone and the Haskell Limestone arbitrarily have been included with the Lawrence Shale. The top of the Haskell Limestone is mapped on Plate 1 as the base of the Lawrence Shale, except where pre-Ireland erosion has cut through the Haskell, in which case the disconformity is mapped as the base of the Lawrence Shale. In areas south of the Worden fault in southern Douglas County where the Toronto Limestone member of the Oread Limestone is missing, the base of the Leavenworth Limestone is mapped as the upper boundary of the Lawrence Shale.
The Lawrence Shale contains two named members, the Ireland Sandstone and the Amazonia Limestone, and two unnamed shales. The formation commonly is 140 to 170 feet thick but locally in the area south of the Worden fault it is only 60 feet thick.
Ireland Sandstone member--The name Ireland Sandstone member is applied to one or more beds of sandstone in the lower part of the Lawrence Shale below the Amazonia(?) Limestone. The sandstone is similar in lithology, color, composition, and texture to the Tonganoxie Sandstone except that it may be slightly coarser. In the subsurface the Ireland Sandstone is light gray where clean and well sorted, and medium or dark gray where carbonaceous material is more abundant. The direction of streamflow during deposition of the Ireland Sandstone member is indicated by the direction of inclination of foreset beds in some outcrops (PI. 5A). The Ireland Sandstone is chiefly very fine to medium (1/16 to 1/2 mm), angular to subangular quartz containing a small percentage of mica, pyrite, and clay minerals and weathers tan or yellow brown. Thin-bedded and shaly parts of the Ireland may contain more clay and silt than sand.
The Ireland Sandstone, ranging in thickness from 0 to about 150 feet, fills a west-southwest-trending erosional valley cut into the Stranger Formation and Weston Shale in southern Douglas County (Fig. 5).
Figure 5.--Generalized map of Douglas County showing location of ancient valley in which Ireland Sandstone member of Lawrence Shale was deposited.
In the headwaters area of Captain Creek the relation of the Ireland Sandstone to the topography over which the sandstone was deposited can be clearly observed. In sec. 21 and 22, T. 14 S., R. 21 E., a deep channel filled with massive crossbedded sandstone and conglomerate trends nearly west along the northern part of each section. The base of the sandstone rises southward and is about 100 feet higher in the southwest corner of sec. 22 (Pl. 3, F-F'). Exposures along Captain Creek near the north side of sec. 21, T. 14 S., R. 21 E., show conglomerate at the base of the Ireland Sandstone in contact with the Weston Shale.
The Ireland Sandstone member was deposited in an ancient erosional valley about half a mile wide cut to a depth of about 100 feet below the Haskell Limestone in southeastern and south-central Douglas County. In an area 5 to 15 miles wide adjacent to the major channel, post-Stranger pre-Ireland erosion cut less deeply into the Stranger Formation and Weston Shale. In this wide area basal deposits of the Ireland Sandstone lie at various positions ranging from 50 feet or more below to about 12 feet above the Haskell, and in most of this area the sandstone adjacent to the principal sandstone-filled area shown in Figure 5 is about 40 feet thick. The Ireland Sandstone thins and becomes shaly in the central and northern parts of Douglas County and can not be differentiated.
Test hole 15-21-4bcc was drilled through 115 feet of Ireland Sandstone having an exceptionally thick conglomerate-nearly 46 feet-in the lower part. The base of the Ireland member is less than 30 feet above the Stanton Limestone, erosion having cut out all the Stranger Formation and most of the Weston Shale. Abundant fragments of detrital coal in the conglomerate and lower part of the sandstone must have been derived from coal beds in the Stranger Formation exposed locally as a result of post-Stranger pre-Ireland and early Ireland erosion. Rich (1932a, 1933) reported the occurrence of abundant coal fragments in the lower part of the Ireland Sandstone in Franklin County and suggested a similar source.
Amazonia(?) Limestone member--The Amazonia(?) Limestone member is doubtfully recognized throughout most of the outcrop area. A few drillers logs indicate a thin limestone in the Upper part of the Lawrence Shale, which may be the Amazonia(?) member. Locally the member may be present as an impure silty limestone or as detrital limestone. Such a detrital limestone, about 4 feet thick and containing considerable coal and shale fragments and having the appearance of a local channel filling, is well exposed near the center of the S1/2 SE1/4 sec. 2, T. 14 S., R. 18 E. (PI. 5B). A similar detrital limestone is present farther north in parts of adjacent Leavenworth County (Reynolds, 1957).
Where a limestone bed is not recognized the member may be represented by a zone of calichelike nodules of limestone about 20 to 45 feet below the top of the Lawrence Shale. Thickness of the member ranges from somewhat less than 1 foot to about 6 feet. Fragments of crinoids and brachiopods, small gastropods, and pelecypods are the common fossils.
Unnamed members--Between the Ireland Sandstone and Amazonia(?) Limestone members there commonly is 5 to 20 feet of sandy and silty gray shale containing the Lower Williamsburg coal. That part of the formation between the Toronto and Amazonia(?) limestone members is chiefly shale and ranges from about 20 to 40 feet in thickness. It contains the thin Upper Williamsburg coal, best developed in the southern half of the county. This upper shale is olive, gray, and greenish gray and in many outcrops has a red or maroon zone, about 2 feet thick, 10 to 25 feet below the top. A bed of very fine grained sandstone several feet thick, partly cemented with calcite, or interbedded sandstone and siltstone occurs locally in the lower part and makes a subdued topographic bench on hillsides. The Upper Williamsburg coal, 0.5 to 1 foot thick, is present about 10 feet below the Toronto Limestone in the vicinity of Lone Star Lake.
Kansas Geological Survey, Geohydrology of Douglas County
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Web version Aug. 1999. Original publication date Dec. 1960.