Pennsylvanian System--Virgilian Series
Wood Siding Formation
As defined by Moore and Mudge (1956, p. 2273), the Wood Siding formation comprises beds formerly assigned to the Brownville, Pony Creek, and Caneyville formations. The first two of these units (two uppermost) were retained by Moore and Mudge as members of the Wood Siding formation.
In Elk County, the Wood Siding formation has an average thickness of about 40 feet. The formation is of little importance as an aquifer.
Brownville limestone member--The Brownville limestone ranges from about 1 to 2 feet in thickness. It commonly is a single massive bed of gray limestone that weathers yellow or brown. Its outcrop is persistent. The rock is characterized by an abundance of fusulinids and the brachiopods Chonetes and Marginifera. It also contains crinoid fragments, echinoid spines, and bryozoans.
Pony Creek shale member--The average thickness of the Pony Creek shale is about 18 feet. Gray brown in the upper part, the shale grades downward into bluish green and yellowish gray. A thin coal bed occurs about 9 feet below the top of the formation. Pelecypods and ostracodes have been observed in the shale.
Grayhorse limestone member--This unit is slightly more than 1 foot thick. It consists of dark-gray massive limestone that weathers buff to yellowish and breaks down into thin wedge-shaped slabs, giving the ledge a distinct cross-bedded appearance. Locally, it is a coquina of small fragments of pelecypods, Myalina being the most common.
Plumb shale member--Plumb is a new stratigraphic name introduced by Moore and Mudge (1956, p. 2275) for shale that formerly was regarded as the middle unit of the Caneyville formation.
This part of the Wood Siding formation ranges in thickness from about 17 to 30 feet. It is bluish-gray to yellowish, micaceous shale, which locally contains some sandstone and thin limestone beds. In the southern part of Elk County, the upper part of the unit contains three limestone beds. The upper one is 0.5 foot thick, dark gray, weathering yellow to rusty, and contains fusulinids. The middle limestone is a 1-foot bed of dark-blue, brownish-weathering limestone crowded with small snails, brachiopods, and bryozoans. The lower limestone is lenticular, dense, and blue, and contains small siltstone pebbles in its lower part. Myalina is abundant in shale above the thin limestones in that area.
Nebraska City limestone member--The Nebraska City limestone is about 1 foot thick. It consists of bluish-gray, dense, locally somewhat impure, massive limestone that weathers buff to orange. Observed fossils include fusulinids, the pelecypod Aviculopinna, crinoid fragments, and small brachiopods.
Moore and Mudge (1956, p. 2275) have defined the Root shale as a formation comprising strata formerly assigned to (in descending order):
French Creek shale, Jim Creek limestone, and Friedrich shale formations; these units now are regarded as members of the Root formation. In Elk County this formation is about 70 feet thick.
French Creek shale member--The average thickness of the French Creek shale is about 37 feet; as much as 42 feet was measured in the northern part of the county. The member comprises gray and greenish to bluish shale and gray to brown sandstone. Locally, the sandstone fills channels. In the northern part of the county, a thin coal bed lies near the top of the unit.
Sandstone in the French Creek shale yields small amounts of water in a few places.
Jim Creek limestone member--The Jim Creek limestone is about 1 foot thick. It is dark blue to bluish gray and massive. The rock weathers purplish, making identification easy. Fusulinids are common and pelecypods are sparse.
Friedrich shale member--The Friedrich shale is about 30 feet thick and consists of gray to bluish shale, which becomes more micaceous and sandy southward in the county. A thin bed of coal occurs about 1 foot below the top of the member. A sandstone ranging from a featheredge to as much as 10 feet thick commonly is seen below the coal bed, but locally the position of the sandstone is occupied by sandy shale. In the northern part of the county, one or more thin pelecypod-bearing limestones occur in the lower part of the formation. Locally, small quantities of water are obtained from the Friedrich shale.
Moore and Mudge (1956, p. 2275) have defined the Stotler limestone as a formation comprising the Grandhaven limestone, the Dry shale, and the Dover limestone as members; these units formerly were regarded as individual formations. In Elk County the Stotler formation averages about 38 feet thick.
Grandhaven limestone member--The average thickness of the Grandhaven limestone is about 10 feet. The unit consists of two or three thin limestones separated by gray and brown shale beds 4 to 11 feet thick. Locally, there is a thin coal bed in the shale. The lowermost limestone bed of the member is dark gray and weathers brown and is less than 1 foot thick. The uppermost limestone is bluish and weathers to a rusty brown. It averages about 1 foot in thickness and contains "Osagia", small brachiopods, and crinoid fragments. Crurithyris, rhomboporid and fenestellid bryozoans, and crinoid fragments are abundant in the shale portion.
Dry shale member--The Dry shale averages about 7 feet thick and consists of gray and brown shale, which is fossiliferous, containing ostracodes, pelecypods, gastropods, bryozoans, and crinoid fragments. A thin coal bed lies in the upper part of the member. The Dry shale carries very little water.
Dover limestone member--The Dover limestone is about 21 feet thick, and it consists of three thin limestones separated by gray, brown, and greenish-gray shale beds. The separating shales are locally fossiliferous. The upper limestone is 2 to 3 feet thick. It is bluish-gray, brown-weathering thin-bedded limestone composed mostly of algal material, "Osagia". The middle limestone is a single bed of dark-gray limestone that characteristically weathers into slabs and contains an abundance of black cryptozoans and slender specimens of Triticites. The lower limestone averages about 1.7 feet in thickness; it is dark blue, dense, and massive, and weathers buff to bright orange. The brachiopod Chonetes is abundant in this lower bed.
Weathered parts of the Dover limestone locally are sources of some water in wells.
Moore and Mudge (1956, p. 2275) have introduced the name Pillsbury as the name of strata between the Dover and Maple Hill limestones.
Because the Maple Hill and Tarkio limestones and the intervening Wamego shale have not been identified as far south as Elk County, strata between the Dover limestone (above) and the Elmont limestone are classed as Willard-Pillsbury. In Elk County the thickness of this part of the section averages about 9 feet and diminishes southward in the county. Lithologically the unit is variable, but one or more thin coal beds are present in all exposures studied. Thin-bedded or slabby limestone, in places overlain and underlain by coal deposits, seemingly is persistent in the northern and central parts of the county, and locally there is a limestone "boxwork" in the lower middle part of the section. The shale commonly is buff to greenish gray. Plant remains are present in the limestone beds that are associated with coal seams, and an assemblage of bryozoans, brachiopods, pelecypods, echinoderm fragments, and ostracodes is characteristic of the upper part of this stratigraphic unit.
Locally, the formation yields some water.
Moore and Mudge (1956, p. 2276) revived the name Emporia limestone. The formation, as defined by Kirk (1896, p. 78-85), includes the Elmont limestone, the Harveyville shale, and the Reading limestone, units that for most of the intervening time were regarded as individual formations. In Elk County the Emporia formation has a thickness of about 22 feet.
Elmont limestone member--The maximum thickness of the Elmont limestone is slightly more than 5 feet. This unit changes markedly in lithology, faunal content, and thickness across the county. At exposures in the northern part, it is slightly less than 2 feet thick, and is bluish-gray, buff-weathering, somewhat massive limestone containing an abundance of small, slender fusulinids. Farther south it is about 5 feet thick, bluish gray, slightly cross-bedded, somewhat conglomeratic, and crinoidal. The Elmont limestone is the source of water in some relatively deep wells.
Harveyville shale member--The average thickness of the Harveyville shale is about 9.5 feet. Gray, micaceous, silty and sandy shale, which contains algal pellets in the upper part and limonitic concretions in the lower and which is streaked with orange, grades southward into bluish- and greenish-gray and reddish clay shale. A thin bed of coal lies in the lower part of the unit in the northern part of the county.
Reading limestone member--The Reading limestone averages 6 feet thick, but in the northern part of the county about 10 feet has been measured where two or three thin limestones separated by shale are present below the more persistent part. This persistent part is a bluish-gray, massive, vertically jointed limestone, about 2.5 feet thick. Locally, as much as 4 feet of thin-bedded, algal limestone lies above the main, massive unit. The shale parts are gray and bluish gray to bluish black. Fusulinids are abundant in the main massive ledge. The lower limestones commonly are abundantly fossilferous, containing fusulinids, bryozoans, ostracodes, and algal remains.
The Auburn shale averages slightly less than 40 feet thick. The formation is variable in lithology, consisting of red, gray, brown, and blue-green, clayey to sandy shale containing thin blue limestones, gray bedded to nodular siltstones, and buff to brown limestone "boxwork". Some of the thin limestones in the middle and lower parts of the Auburn shale are fossiliferous. This formation is unimportant as an aquifer.
The Bern limestone (Moore and Mudge, 1956, p. 2276) includes the Wakarusa limestone, Soldier Creek shale, and Burlingame limestone, formerly classed individually as formations. In Elk County the Bern formation is about 12 feet thick.
Wakarusa limestone member--The average thickness of the Wakarusa limestone is about 5 feet but 7.7 feet was measured in the southern part of the county and only 2 feet in the northern part. Light bluish-gray fusulinid- and algal-bearing limestone is characteristic. Where thickest, the member includes about equal amounts of gray shale and limestone. The shale occurs in the middle part. The Wakarusa limestone locally yields some water.
Soldier Creek shale member--The Soldier Creek shale is commonly slightly less than 3 feet thick and consists of bluish- and greenish-gray clay shale locally streaked with yellow. It is sparingly fossiliferous, crinoid fragments and ostracodes being the most plentiful forms.
Burlingame limestone member--The Burlingame limestone averages about 3 feet thick. It is thinner and somewhat more massive in the northern part of the county than in the southern part. The rock is commonly brown, algal in its upper par, and fusulinid bearing in the lower part. Locally, in the southern part of the county, the two parts are separated by slightly less than 1 foot of gray, calcareous, algal shale. In addition to "Osagia" in the upper part and small fusulinids in the lower, echinoid fragments, bryozoans, brachiopods, and pelecypods are fairly common fossils in the formation.
Strata between the base of the Burlingame limestone and (downward) the top of the Howard formation (Utopia limestone) are included in the Scranton shale (Moore and Mudge, 1956, p. 2277), In Elk County the Scranton formation has a thickness of about 125 feet.
Silver Lake shale member--The Silver Lake shale averages about 40 feet thick. The member consists of gray shale and includes thin, platy, impure, pelecypod-bearing limestone beds in the upper part. The lower part is sandy and micaceous and contains thin sandstone lenses and sandy concretions. Vertical jointing is common in the lower part. In the northern part of the county, there is a thin coal bed about 15 feet below the top of the member. Locally, channel-filling sandstones carry some water.
Rulo limestone member--The Rulo limestone averages slightly less than 1 foot in thickness. It is dark gray and weathers brown and platy. Its upper part, at least locally, is algal. Fossils are not plentiful in the Rulo limestone, but the alga "Osagia", productid and spiriferid brachiopods, gastropods, and echinoderm fragments are present. Seemingly the Rulo limestone has been removed locally by intraformational erosion (Fig. 4, stratigraphic section 8).
Cedar Vale shale member--At out 30 feet is the average thickness of the Cedar Vale shale. The member is poorly exposed; it, with the overlying Silver Lake shale, almost everywhere is concealed by long, grass-covered slopes. The position of the separating Rulo limestone is marked by a slight bench about midway between the Burlingame and Happy Hollow limestones. Almost all of the upper part (about 1 foot) of the Cedar Vale is gray shale containing marine fossils in the upper part and sparse land plant fossils in the lower part. Next below is a thin coal bed, the Elmo. Sandy shale or thin-bedded sandstone, below the Elmo coal, grades downward into more clayey, gray and yellow shale. Locally, sandstone in the Cedar Vale shale carries some water.
Happy Hollow limestone member--The thickness of the Happy Hollow limestone ranges from about 2 to 10 feet and most commonly is about 3 feet. In most exposures the member comprises one or more massive beds of pinkish-brown, massive limestone containing abundant large fusulinids. The member is unusually thick in sec. 8, T. 30 S., R. 10 E., where it consists of 11 feet of light-gray to buff limestone, massive in the lower part but irregularly bedded in the upper part. The increase in thickness is due to accumulation of algal material.
White Cloud shale member--The thickness of the White Cloud shale is about 50 feet. Where best exposed, approximately 30 feet in the upper part is gray to yellowish brown, finely laminated, and micaceous; the uppermost part is sandy. The lower part of the White Cloud member comprises dark gray to black shale and limestone beds ranging from a featheredge to a few inches in thickness. Algal remains, corals, ostracodes, and brachiopods are present as fossils in the limestone and shale beds in the lower part of the unit. Sandy parts of the White Cloud carry some water.
In Elk county the Howard limestone is 11 to 12 feet thick. The formation includes three limestone and two shale members. A persistent coal bed is present in the lower shale member. A few shallow wells obtain water from weathered parts of the formation.
Utopia limestone member--The average thickness of the Utopia limestone is about 5 feet. The rock is dark bluish gray and weathers rusty brown, buff, or bright orange. Locally, it is nearly a coquina of shell fragments and algal remains. Thin bedding is characteristic of the ledge.
Winzeler shale member--In all exposures where studied, the Winzeler shale is less than 2 feet thick, and in several places the unit was observed to be little more than a thin shale parting between the overlying and underlying limestones. In the thicker sections the Winzeler shale is yellowish brown and clayey.
Church limestone member--The Church limestone averages only about 2 feet thick, but inasmuch as it is massive and resistant to weathering, it is the most prominent part of the Howard formation. The rock is dark bluish gray, hard, and dense. Weathered surfaces are bright brown to buff. Fusulinids are common, and other fossils are fairly plentiful.
Aarde shale member--In measured sections the Aarde shale ranges from 1.6 to about 5 feet in thickness. It comprises gray and black fissile shale in the upper part and a thin coal bed (the Nodaway), gray shale, and underclay in the lower part. Locally, south of T. 30 S., a thin bed of dark-gray limestone occurs a short distance above the coal bed.
Bachelor Creek limestone member--The Bachelor Creek limestone averages slightly less than 3.5 feet thick. It is light to dark bluish-gray limestone that weathers dark gray and buff. The rock is silty and impure and contains echinoderm fragments, pelecypods, and brachiopods.
The Severy shale averages about 70 feet in thickness; it is composed of gray to buff, silty and sandy, micaceous shale, the upper part of which locally contains lenses and nodules of hard, bluish-gray siltstone and sandstone. The lower part commonly is laminated gray silty and sandy shale including yellowish and bluish streaks. Vertical jointing is common in the lower part, which locally contains some red clay. South of the town of Howard, hills that lie east of the Howard limestone escarpment are capped with bluish-gray siltstone in the upper part of the Severy. The Severy shale does not carry important amounts of water.
In Elk County the Topeka limestone has a thickness of 40 to 50 feet. Of the nine members recognized within the formation farther north in Kansas, only the upper and lower ones are differentiable in Elk County.
Coal Creek limestone member--The upper-most division of the Topeka formation in Elk County is a persistent fusulinid-rich limestone that, according to R.C. Moore (personal communication), is traceable into the Turkey Run limestone of the Pawhuska formation in northern Oklahoma. It is here called Coal Creek limestone, however, because it occupies the position of the topmost member of the Topeka formation farther north. Its thickness in Elk County ranges from about 5 to 8.5 feet. The rock mainly is dark to brownish gray and weathers buff to gray. The ledge is thin and wavy bedded. It is characterized by abundant, large fusulinids. Algae are numerous in places at the top. Common fossils include "Osagia", Triticites, rhomboporid bryozoans, brachiopods, and echinoderm fragments. Several species of pelecypods and a small, high-spired gastropod are present in the lower part.
Undifferentiated shale and limestone--The middle part of the Topeka formation in Elk County, comprising shale and limestone about 35 feet thick, is not classifiable in terms of member divisions recognized in northern Kansas and Nebraska. Hence, in this report strata between the Coal Creek member and the bottom limestone member (identified as Hartford) are undifferentiated. They correspond in stratigraphic position to the members that in the north have been named (in downward order) Holt shale, DuBois limestone, Turner Creek shale, Sheldon limestone, Jones Point shale, Curzon limestone, and Iowa Point shale. It is pointless to describe features that distinguish these units farther north because they are all foreign to the middle Topeka succession in Elk County.
The upper part of the undifferentiated Topeka beds as just defined consists of 15 to 23 feet of predominantly shaly strata characterized by the abundance and variety of invertebrate fossils found at most outcrops. These include especially abundant Chonetes shells and very slender small fusulinids (Triticites), which may lie closely together in alignment on thin limestone plates; common Neospirifer, Echinoconchus, Dictyoclostus, Juresania, and other brachiopods; and a profusion of well-preserved small gastropods and pelecypods. Crinoid remains and ammonoids are less common. A zone of abundant slender ramose bryozoans (Rhombopora) occurs commonly at the top of the shale, just below the Coal Creek limestone. Most of the shale is light ash gray in fresh exposures; but some layers are yellowish, and weathered outcrops are gray to brownish. Earthy to silty limestone occurs as plates, as nodules, and in thin beds a fraction of an inch thick. Some beds are calcareous fossiliferous siltstone, which breaks with irregular conchoidal fracture. According to Moore (personal communication), this shaly division of the Topeka formation is widely distributed in Chautauqua and Greenwood counties, to the south and north of Elk County, respectively.
Next below the fossiliferous shaly unit is a fairly persistent brown-weathering limestone, which is blue gray to dark blue in fresh exposures. The topmost bed is massive and hard, has an even upper surface, and contains abundant "Osagia". Lower beds lack "Osagia" but carry brachiopods and, in places, fairly numerous robust fusulinids. This division, about 3 to 5 feet thick, which may represent the Curzon member, overlies light-tan, fine-grained sandstone or very sandy shale at some outcrops, especially in the vicinity of Moline, and this sandy zone aids in distinguishing the limestone.
Beneath the sandstone is 3 to 5 feet of bluish silty to clayey unfossiliferous shale. Generally this is a covered zone. It is the basal division of the undifferentiated Topeka beds.
Hartford limestone member--The lowermost Topeka member in Elk County consists of thin-bedded, fine-grained, blue-gray to dark-blue limestone, the basal 0.5 to 1 foot of which is characterized especially by abundance of large algal colonies (Ottonosia) associated with the chambered sponge Amblysiphonella. The thin-bedded strata locally contain fusulinids, but in some outcrops search fails to discover these fossils. The Ottonosia-Amblysiphonella bed is an extremely persistent marker, which has been identified by Moore from northern Kansas to Oklahoma, and it serves to define the lower boundary of the Topeka formation.
In Elk County the Calhoun shale is almost non-existent, for the maximum thickness of shaly strata between the basal Topeka Ottonosia-Amblysiphonella bed and the "Osagia"-bearing, easily identified top of the Ervine Creek limestone (uppermost member of the Deer Creek formation) is barely 5 feet. This section is not commonly exposed. Where well exposed, this sequence is seen to consist of unfossiliferous dark-blue to drab, silty to clayey shale. Near Moline and east of Howard, this shale is less than 0.5 foot thick, and locally it is absent.
The Calhoun shale is of no importance as an aquifer.
Deer Creek Limestone
The Deer Creek limestone is 55 to 70 feet thick. The formation includes three limestone and two shale members. The upper member, the Ervine Creek limestone, caps a pronounced escarpment across the east-central part of Elk County.
The Deer Creek formation is an important aquifer in a large area where it lies at shallow depth. Springs are present along its outcrop.
Ervine Creek limestone member--The Ervine Creek limestone in Elk County is about 15 to 25 feet thick. Where best exposed, in a quarry northeast of Moline, it consists of 23 feet of nearly uniform fossiliferous light-gray limestone. The top is a massive osagite bed having an even upper surface. The member is darker gray near the top and lighter gray and somewhat uneven bedded in the lower part. There are numerous very thin, dark shale partings that separate the massive beds. The member is characterized by robust fusulinids. Other marine invertebrates are also well represented.
Larsh-Burroak shale member--The Larsh-Burroak shale averages about 3 feet in thickness. It is gray and bluish gray in the upper part and black and fissile in the lower part.
Rock Bluff limestone member--The Rock Bluff limestone ranges in thickness from 1.5 to 2 feet. It is dark-bluish, hard, brittle limestone occurring commonly in one vertically jointed bed. The rock weathers into sharp, angular blocks. Fusulinids are the most numerous and characteristic fossils.
Oskaloosa shale member--The thickness of the Oskaloosa shale averages about 28 feet, but as much as 34 feet was measured. The member is mostly red to green and purplish shale containing sandstone lenses and plates. Locally, sandstone in the upper middle part is cross bedded, and it may be thick enough and hard enough to be prominent topographically. In some exposures there is a 4-foot bed of greenish to dark-gray algal limestone about 2.5 feet above the base.
Ozawkie limestone member--The lower member of the Deer Creek formation averages about 2.5 feet thick. It comprises two or three beds of limestone separated by gray-brown, yellowish, or locally red and green shale. Bluish-gray, mottled algal and fusulinid limestone is characteristic.
The Tecumseh shale consists mostly of sandy and silty gray shale, red, green, and bluish-gray shale, and sandstone. Its average thickness is about 45 feet. Locally, the upper 15 to 20 feet consists of thin to fairly massive, cross-bedded layers of gray sandstone, which weathers buff and reddish. A thin bed of limestone occurs about 12 feet above the base of the formation. The shale below this limestone is more clayey than that above. It contains occasional calcareous nodules, and pelecypods are common in its upper part. Sandstones in the Tecumseh formation, in an area south and west of Elk Falls, yield considerable amounts of ground water.
The thickness of the Lecompton limestone is about 55 feet. The formation contains four limestone and three shale members. Small supplies of water are obtained locally from the weathered upper part of the formation.
Avoca limestone member--The Avoca limestone averages about 8.5 feet in thickness. The upper part, commonly less than 1 foot thick, is dark-gray shelly limestone underlain by less than 1 foot of gray-brown fossiliferous shale. The most persistent and characteristic part lies next below. It is a limestone bed about 1 foot thick, hard, dense, brittle, vertically jointed and containing abundant cryptozoans (Ottonosia), which always are associated with Amblysiphonella. Thus, this unit duplicates characters of the basal Topeka (Hartford member) bed. The lower part consists of about 1.6 feet of gray, clayey, fossiliferous shale underlain by about 4 feet of blue-gray, wavy-bedded limestone that weathers brown and contains abundant fusulinids. Other marine invertebrates also are well represented in the Avoca member.
King Hill shale member--The thickness of the King Hill shale ranges from about 5 to 10 feet. The member contains a considerable amount of red and greenish-gray clay, but where thin it is composed principally or wholly of gray and bluish shale.
Beil limestone member--The Beil limestone has an average thickness of about 9 feet. In some exposures about 7 feet of gray to cream, yellow-weathering, massive to thin-bedded limestone is separated below by about 1.5 feet of gray shale from 1 foot of bluish-gray, dense limestone. In other places there is 2 feet of thin, irregularly bedded, yellow-weathering limestone underlain by about 9 feet of bight-gray, cream weathering limestone that is especially massive in its upper part. Corals, characteristic of the Beil in many places, are not particularly abundant in Elk County. Somewhat common fossils are robust fusulinids, corals, bryozoans, and brachiopods.
Queen Hill shale member--The average thickness of the Queen Hill shale is about 3.5 feet. The unit thickens southward, and the greatest thicknesses were measured in localities where the underlying Big Springs limestone and Doniphan shale are unusually thin. This member is composed principally of dark-gray clayey shale. Black, fissile shale occurs in the middle part of the member in Chautauqua County, and although not observed in southern Elk County, it is probable that this lithology extends that far.
Big Springs limestone member--The Big Springs limestone has an average thickness of about 4.5 feet. The upper part is massive, dense, and vertically jointed. The lower part commonly is composed of one or more thin beds of limestone and thin shale layers. Locally, the lowermost part is a calcareous sandstone, and in all places where studied it is somewhat sandy. Fossils include fusulinids, ostracodes, and rhomboporid and fenestellid bryozoans.
Doniphan shale member--The thickness of the Doniphan shale averages about 23 feet but in measured sections ranges from 18 to 28 feet. This unit comprises gray to buff, silty and sandy shale and sandstone. In places the upper part is mainly greenish-gray, slightly cross-bedded sandstone, and locally the middle part contains several thin sandstone beds. In some places, sandstone is thick, hard, massive, and topographically prominent.
Spring Branch limestone member--The average thickness of this lowermost member of the Lecompton formation is slightly more than 4 feet. In general, there is a slight decrease in thickness southward across the county. At some exposures the unit consists of three massive limestone beds separated by thin layers of slabby or nodular limestone. This facies comprises an upper bluish-gray, dense, algal and fusulinid limestone; a middle bed of sandy impure limestone that weathers brown or orange; and a lower massive, algal limestone that weathers into irregular slabs. In other places there is an upper bed less than 2 feet thick that is mottled light gray and contains abundant "Osagia", and a lower bed of bluish-gray sandy limestone about 1.5 feet thick. These two beds are separated by about 1.5 feet of gray shale.
In southern Elk County and in neighboring parts of Chautauqua County, the section between the base of the Lecompton formation and the top of the Plattsmouth limestone is 125 to 135 feet thick. Seemingly, this section includes beds that are equivalent to the Kereford limestone and Heumader shale, which farther north are classed as the upper two members of the Oread formation, but which have not been identified in this area. Furthermore, the Clay Creek limestone, which farther north separates the upper member, the Stull shale, from the Jackson Park shale, has not been identified in southern Elk County. In northeastern Elk County, where the three members of the Kanwaka formation have been identified, the thickness of the formation is about 90 to 100 feet. Sandstone is quantitatively important in the formation in both parts of the county. The Elgin sandstone, in the lower part of the formation, is one of the most important aquifers in Elk County.
Stull shale member--The average thickness of the Stull shale in northeastern Elk County is about 30 feet. In an exposure in sec. 21, T. 28 S., R. 12 E., the member is about 35 feet thick. The following units are differentiated and are regarded as somewhat characteristic for the area: 8 feet of greenish-gray clay shale containing a zone of red clay in the middle part; 6 feet of thin, buff, fossiliferous limestone interbedded with gray shale containing fossil plants; and 21 feet of shale, orange and buff in the upper part, but grading downward through bluish-gray, pelecypod-bearing shale into green and red or bluish and buff shale and including a few thin beds of limestone about 7 or 8 feet from the base. These beds of limestone contain Chonetes.
Clay Creek limestone member--In northeastern Elk County, the Clay Creek limestone has an average thickness of about 4.5 feet. The upper part consists of as much as 3 feet of thin, gray, slabby, coquinoid limestone interbedded with gray shale. The lower part consists of as much as 3 feet of thin-bedded, buff to orange, fusulinid-bearing limestone, interbedded with gray and buff shale. Elsewhere in the area the member is thinner and comprises gray, pelecypod-bearing limestone and shale. The lower part of the unit characteristically is sandy. Seemingly, the Clay Creek limestone pinches out in southern Elk County, or inasmuch as the lower part becomes increasingly sandier southward, more probably the rock is represented by one of several thin sandstone beds that lie about 30 feet below the top of the Kanwaka formation.
Jackson Park shale member--The Jackson Park shale in northeastern Elk County ranges from 40 to 50 feet in thickness. The upper part consists of bluish-gray or reddish clay and is underlain by buff to yellowish-gray or gray, massive, cross-bedded sandstone. The lower part of the sandstone body locally fills channels. At some exposures the base of the channels is near the top of the Kereford limestone, and in some places the base of sandstone beds lies only a few feet above the Plattsmouth limestone, suggesting that the Kereford limestone and a part of the Heumader shale were removed by erosion before deposition of the sand. In places where the channels are less deep, the lower part of the Jackson Park shale consists of gray to tan, silty and sandy shale and thin sandstone beds.
In southern Elk County, where the Stull and Jackson Park shales are not differentiated, sandstone 50 to 75 feet thick extends downward nearly to the top of the Plattsmouth limestone. This is the Elgin sandstone, which is believed to be properly regarded as a part of the Jackson Park member.
The Oread formation is about 120 feet thick in Elk County. All of the four limestone and three shale members are represented, and all but the upper two members are well exposed. The Plattsmouth and Snyderville members are of some importance as aquifers.
Kereford limestone member--The Oread formation crops out in northeastern and southeastern Elk County, but only in the northeastern part has the Kereford limestone been recognized. In the area where it has been identified, the Kereford limestone is slightly less than 1 foot thick and consists of dark-gray shaly limestone weathering buff and gray that occurs in two beds separated by gray shale. Both limestone and shale contain fusulinids.
Heumader shale member--In localities in northeastern Elk County where the Heumader shale has been identified, it is about 16' feet thick. The upper part is bight gray, is silty to sandy, and contains numerous well-preserved specimens of the small pelecypod Astartella. The lower part, ranging from about 2 to 8 feet in thickness, is fossiliferous gray shale, locally containing a thin, fusulinid-bearing limestone bed. In southern Elk County, fossiliferous shale above the Plattsmouth limestone may be the Heumader shale member of the Oread formation.
Plattsmouth limestone member--The Plattsmouth limestone averages about 15 feet in thickness, but as much as 18 feet was measured. It consists of light-gray limestone in irregular beds. The upper few feet consists of wavy beds of soft, impure limestone separated by thin shales. The middle part is bluish gray, brittle, and dense but becomes more crystalline and lighter in color downward. The lower 4 or 5 feet consists of dense gray limestone that weathers buff or brown. These lithologic units are not sharply defined but grade into one another. The Plattsmouth limestone contains a mixed fauna of marine invertebrates including fusulinids.
Heebner shale member--The Heebner shale is about 4.6 feet in thickness. The upper, part is characteristically gray or brownish, and the lower part is black and fissile. The black part is about 3 feet thick in all exposures studied in Elk County. Marine invertebrate fossils occur in the zone of transition between the gray and black parts.
Leavenworth limestone member--The thickness of the Leavenworth limestone averages about 1.3 feet and ranges from 1.0 to 1.8 feet. This unit is a single, massive bed of dark-blue, dense, brittle limestone that has prominent vertical joints. Weathering produces a buff or orange veneer. The most numerous fossils-are small fusulinids. Small brachiopods and fragments of echinoderms are less plentiful.
Snyderville shale member--In measured sections the Snyderville shale ranges in thickness from about 60 to 68 feet. The unit comprises principally red, green, and bluish shale, greenish-gray siltstone, and sandstone. In the northeastern part of the county, this member is red, buff, and light-gray shale and includes about 12 feet of buff to yellow sandstone in the upper part and a few sandstone lenses and ironstone concretions scattered through the lower 45 feet. In the southeastern part, approximately the lower half of the Snyderville is gray, thin-bedded and cross-bedded, fine-grained, micaceous sandstone containing a small amount of sandy shale.
Toronto limestone member--The thickness of the Toronto limestone ranges from about 6 feet in northeastern Elk County to 2 feet or less in the southeastern, part. In the northern area, the member consists of thin beds of limestone separated by shale partings. A molluscan bed is near the top, and the other beds bear fusulinids. In the southern area, where the Toronto is less than 2 feet thick, it consists of two molluscan limestones separated by a bed of bluish-gray shale.
The thickness of the Lawrence shale ranges from 90 to 170 feet. Units definitely recognized in Elk County are: a clay shale in the upper part, the Amazonia limestone, and the Ireland sandstone in the lower part. The Ireland sandstone is one of the most important aquifers in Elk County.
Unnamed shale unit--A sequence of 60 to 65 feet of rock, mostly beds of shale, lies below the Toronto limestone and above the Amazonia. Exposures of this part of the stratigraphic section are poor. In general, the sequence comprises gray to buff, silty or sandy shale, and a small amount of gray, greenish-gray, and buff sandstone. A thin coal bed lies about 2 feet below the top of the formation. Shale above the coal is crowded with fusulinids in the upper part and contains a prolific pelecypod fauna in the lower part.
Amazonia limestone member--The Amazonia limestone averages slightly less than 5 feet thick, but as much as 9 feet was measured. The thickness decreases southward. Where the rock is thickest, it consists of thin, slabby, irregular beds of dark-gray to bluish-gray, light-weathering, extremely fossiliferous limestone. Elsewhere it is reduced to a bed of fusulinid-bearing limestone less than 2 feet thick. In some places the unit is shaly and sandy in its lower part. Common fossils in the Amazonia are marine invertebrates and algae.
Ireland sandstone member--In this part of Kansas, the Ireland sandstone is regarded as including beds that lie next below the Amazonia limestone; in some other places, an unnamed shale lies between the Amazonia and Ireland members. The thickness of the Ireland sandstone ranges from about 30 to perhaps as much as 100 feet. The sandstone is interpreted as being a deposit that accumulated on an irregular erosional surface and as consisting of a series of channel fills that grade laterally into a more extensive but thinner sheet-like deposit that lies above divides between channels. In the deeper channels the measurable thickness is about 80 feet. The rock consists principally of gray to reddish or buff, fine-to medium-grained sandstone. Where the sandstone fills channels, the contact with the underlying Robbins shale is sharp; elsewhere it is less well marked.
The Stranger formation ranges in thickness from about 65 to 130 feet. It includes two limestone, one sandstone, and two shale members. Small supplies of ground water are obtained from the formation.
Robbins shale member--The thickness of the Robbins shale ranges from 65 to 112 feet. In localities where the Ireland sandstone is relatively thin and seemingly is a sheet-like deposit over divides on the post-Robbins erosional surface, the Robbins shale is thick; the contact between the Ireland and Robbins may not be sharply defined, however. Throughout the area of outcrop, the two units have a uniform combined thickness of about 150 feet. The Robbins shale consists of gray to bluish, clayey to silty, blocky shale in its lower part but grades upward into silty and sandy shale and gray to yellowish to reddish-gray sandstone.
Haskell limestone member--The Haskell limestone is a persistent, massive limestone and has an average thickness of about 1.5 feet. The thickness decreases southward. This rock is about 2.6 feet thick in neighboring parts of Wilson County (east of Elk County) and about 0.8 foot thick in northeastern Chautauqua County. The Haskell is dark bluish-gray, hard limestone that weathers buff. Abundant dark-gray to black, irregularly layered bodies are believed to be algal colonies.
Vinland shale member--The Vinland shale averages about 18 feet in thickness. It thickens southward, from about 4 feet in west-central Wilson County to about 35 feet in northeastern Chautauqua County. The upper part is composed of yellowish and gray shale that grades downward into greenish gray. Poorly preserved specimens of the pelecypod Myalina are present in the upper part of the unit in southeastern Elk County; in the northeastern part of the county, the unit is more calcareous and more abundantly fossiliferous, carrying fenestellid bryozoans, small brachiopods, and crinoid fragments.
Westphalia limestone member--The Westphalia is a discontinuous, dark-gray, sandy to shaly, fusulinid-bearing, algal limestone and has an average thickness of slightly less than 3 feet. It is slightly thicker in the northeastern part of the county than it is in the southeastern part. In the northern area the thickness ranges from a featheredge to nearly 5 feet; but locally the limestone is absent, and about 15 feet of gray, yellow, and greenish shale lies between the Haskell limestone and the Tonganoxie sandstone. The Westphalia, although fusulinid bearing, contains a relatively barge amount of clastic material, including fragments of coaly material, mica flakes, silt, and fine sand. Fossils other than fusulinids include algae, fragments of crinoids and other fossils, and productid and spiriferid brachiopods.
Tonganoxie sandstone member--The thickness of the Tonganoxie sandstone ranges from about 2 to 40 feet. In the southeastern part of Elk County, the unit is thin, greenish gray, brown weathering, and calcareous. Worm borings and castings are numerous. Only the upper part of the Tonganoxie sandstone is exposed in the northeastern part of the county, but the member is thicker there. The thin veneer of sandstone in the southeastern part probably was deposited on a divide between channels, and it is probable that shale, equivalent in age to a part of the Tonganoxie member, rests directly on some part of the Weston shale.
Pennsylvanian System--Missourian Series
The maximum measured thickness of the exposed part of the Weston shale, oldest outcropping rock in Elk County, is about 22 feet. The rock is gray to greenish-gray, clayey to silty shale, bearing small limonitic concretions.
Kansas Geological Survey, Geology
Web version July 2002. Original publication date July 1958.
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