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Stanton Formation

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Typical Stanton Limestone in Eastern Kansas

In the open-marine facies belt throughout northeastern Kansas, the members of the Stanton Limestone are relatively uniform laterally. Distinctive characteristics of the five members in this region are summarized from Newell (1935), Moore (1949), Ball (1959), and personal observations, and are illustrated by a standard section measured along the Kansas Turnpike west of Kansas City (Fig. 3A). Most members undergo moderate lateral change southward in the algal-mound facies belt which extends from Anderson to northern Montgomery counties (Fig. 2); these changes are summarized from Heckel and Cocke (1969, p. 1073) and personal observations. Although the members there locally vary laterally more than they do northward, they are illustrated by a standard section measured in a 1965 roadcut northwest of Independence (Fig. 3B). Because this is the best-exposed complete section known in the algal-mound facies belt and is located near the detrital facies belt, it affords an excellent section with which to correlate the units recognized in the detrital belt. The members are described in ascending order.

Figure 3--Measured sections of Stanton Limestone in eastern Kansas (located on Figure 2) showing both subdivision into five named members that are recognized from Nebraska to southeastern Kansas and their generalized component facies in Kansas; A. Standard section in northeastern Kansas on north side of Kansas Turnpike, 1.2 mile west of Bonner Springs interchange (sec. 18, T. 11 S., R. 23 E., Wyandotte Co.); B. Standard section in southeastern Kansas, on north side of road about 1 mile west of Elk City dam (south of ctr N half 7-32-15, Montgomery Co.); C. Section near Mont Ida in east-central Kansas in west bank of Cedar Creek just north of Missouri Pacific Railroad trestle (NW-SE-NE 17-21-19 Anderson Co.); Captain Creek Member measured in north bank of Pottawatomie Creek (ctr NE-NE 5-20-19) about 5 miles northwest of Garnett, Anderson County. A larger version of this figure is available.

Three measured sections.

Captain Creek Limestone Member

At the base of the Stanton, the Captain Creek Member is a 4- to 6-foot-thick ledge of medium-bedded, skeletal calcilutite in northeastern Kansas where it carries a marine fauna of brachiopods (with conspicuous Enteletes), echinoderm pieces, fenestellid bryozoans, molluscs, fusulinids, phylloid algae, and osagia encrustations.

Southward the Captain Creek thickens through 12 feet in Anderson County to about 45 to 50 feet in northern Montgomery County, where it holds up the prominent escarpment and the outlier of Table Mound northwest of Independence. Coincident with this thickening is an increase in the amount of phylloid algae, which greatly dominates the biota where the unit forms a phylloid-algal mound complex throughout most of southeastern Kansas. Internal structure of most of the phylloid algae has been obliterated by recrystallization, but both green codiaceans (Anchicodium) and red ancestral corallines (Archaeolithophyllum) have been identified locally. Separating discrete buildups within the complex in Woodson and Wilson counties are contemporaneous channels at least 12 to 22 miles long and 0.5 to 1 mile wide (Heckel 1966; 1972a, p. 589). Where it can be differentiated within these channels, the Captain Creek is thinner, less algal, and several tens of feet lower topographically than in the adjacent buildups. Within the buildups the Captain Creek displays "mound" facies which typically appears massive and vuggy on outcrop. Mound facies consists largely of sparry algal calcilutite in which algal blades shelter spar-filled voids from complete infilling by lime mud through the umbrella effect described by Harbaugh (1960, p.204).

Throughout the south end of the buildup in northern Montgomery County, much of the upper one-half is algal sparite with extremely coarsely crystalline, brownish and whitish calcite and greatly subordinate calcilutite. At the standard section (Fig. 3B), thinner-bedded layers of skeletal calcilutite occur at the base and intercalated at two horizons within the mound facies. In the top of the buildup in this region are small channels, 8 to 12 feet deep, containing thin-bedded skeletal calcarenite and calcilutite, in places intercalated with fossiliferous shale.

Eudora Shale Member

Overlying the Captain Creek, the Eudora Shale Member averages about 7 feet thick in northeastern Kansas. Its most distinctive feature is the presence of several feet of black fissile shale that contains phosphorite nodules and occupies most of the lower one-half of the unit. The black shale carries mainly conodonts, fish scales, and orbiculoid brachiopods. The remainder of the member is gray shale that carries scattered snails, clams, articulate brachiopods, and conularids. Although thinning locally to less than 1 foot in northern Anderson County, the black shale in the Eudora seems continuous southward to the vicinity of Mont Ida in central Anderson County where about 3 feet is exposed (Fig. 3C), and perhaps into northern Allen County where Miller (1969, p. 15, 16) reports about 2 feet of gray shale with lenses of black fissile shale in the base. Southwest of these localities, in the algal-mound facies belt, black shale is found at the Eudora horizon only within the large contemporaneous channels in Woodson and Wilson counties.

Elsewhere in this region above the Captain Creek algal buildups, a horizon of fossiliferous gray shale and thin-bedded limestone is exposed in places separating the massive Captain Creek from the next higher limestone member (Stoner). This shaly horizon has been called Eudora by previous writers (e.g. Newell, 1933, p. 80 ff.; Wagner, 1954, 1961). Five feet of similar shale occurs at the Mont Ida section grading upward into thin-bedded shaly limestone of the Stoner (Fig. 3C). Although this gray shale lies above definite black Eudora, it is separated from it by a 2.5-foot ledge of skeletal calcilutite. Thus, the fossiliferous gray shale could be considered to lie within the lower part of the Stoner, but because it constitutes the only marker unit between Captain Creek and definite Stoner in this region of thick limestone members, this gray shale is referred to as "Eudora" until its exact stratigraphic placement is better delineated (no quotes are used, however, if black shale accompanies the gray shale). In the few places where it is exposed in Wilson County, the gray "Eudora" consists of one to several feet of fossiliferous soft clayey shale intercalated with thin layers of skeletal calcilutite and calcarenite. The lowest shale lies with sharp contact, locally marked by small phosphorite nodules, upon the Captain Creek. Fossils are predominantly brachiopods (including productids, Composita, Neospirifer, and Hustedia), fenestellid and cylindrical bryozoans, echinoderm pieces, and less commonly, fusulinids and horn corals.

Southward, at the standard section (Fig. 3B), on the south edge of the algal-mound facies belt, the Eudora interval is largely covered. About 24 feet above the top of the Captain Creek, a 3-foot exposure of typical "Eudora" soft gray-green fossiliferous shale grades upward through shaly limestone into typical Stoner. In the interval below the shale, several feet of thin-bedded invertebrate-rich calcilutite, distinct from the generally massive Captain Creek algal mound are included in the "Eudora" interval. On the basis of lithology, the shalier portion of fill in the minor channels at the top of the massive Captain Creek mound might also be considered "Eudora."

Stoner Limestone Member

Above the Eudora Shale lies the Stoner Limestone Member, which, along with the two overlying members of the Stanton, was named from Nebraska. In Kansas, the Stoner was formerly termed Weaver (Newell, 1933) and Olathe (Moore, 1936) before correlation with Nebraska was established. In northeastern Kansas, the Stoner ranges from 11 to 15 feet of wavy, thin to medium-bedded skeletal calcilutite grading upward to calcarenite. Fossils include brachiopods of several types, echinoderm debris, bryozoans and fusulinids.

The Stoner maintains these characteristics southward to northern Anderson County. At the Mont Ida section (Fig. 3C), it is thickened to about 25 feet, with the lower 8 feet transitional downward to "Eudora" gray fossiliferous shale, and the upper 12 feet developed as a massive phylloid-algal limestone typical of the algal-mound facies belt. Although it is difficult to obtain a complete section of the Stoner southward across this belt, thickness seems generally to exceed 15 feet, and as much as 40 feet has been estimated in the Elk River Valley of northwestern Montgomery County, west of the standard section. Throughout most of the algal-mound facies belt, much of the Stoner is algal calcilutite of the mound facies. In contrast to the massive, vuggy Captain Creek in this facies belt, however, Stoner mound facies tends to be thin to medium-bedded in layers that weather less vuggy. Algal blades tend to be smaller, more like small potato chips, and other less algal rock types are more common than in the Captain Creek. The lower few feet tend to be shaly and rich in invertebrate fossils in the downward transition to the "Eudora." Along both the mound buildup rim and the major channels in Woodson and Wilson counties, the Stoner Member is mostly abraded-grain skeletal calcarenite.

At the standard section (Fig. 3B), the Stoner is only 20 feet thick. The lower portion is thin-bedded and shaly, with a biota dominated by marine invertebrates. Bedding becomes thicker in the middle, where algae become more common, and fusulinids are abundant. The upper several feet are massive and dominated by phylloid algae that shelter spar-filled voids. The codiacean Eugonophyllum has been identified here, and the ancestral coralline Archaeolithophyllum was found nearby.

Rock Lake Shale Member

Overlying the Stoner Limestone with a sharp contact everywhere, the Rock Lake Shale Member was previously referred to in Kansas as Wolf Creek (Newell, 1933) and Victory Junction (Moore, 1936). In northeastern Kansas, the Rock Lake ranges from 3 to 14 feet thick. Although it consists mainly of light brown, silty, micaceous shale at the standard section (Fig. 3A), it is the most heterogeneous member of the Stanton; elsewhere in this region it contains various amounts of clay shale, impure platy limestone, and reddish-brown sandstone that in places dominates the member. Fossils consist chiefly of plant fragments, tracks, trails and burrows, but pelecypods are locally abundant.

Southward, the Rock Lake Shale is thin and poorly exposed over most of the algal-mound facies belt. Where exposed above mound facies of the Stoner from central Anderson to northern Montgomery counties, it is typically 1 to 2 feet of nearly unfossiliferous light gray shale. [Note: One locality in northern Anderson County, however, yields a remarkable assemblage of land plants and brackish-water to marine invertebrates (Moore et al., 1935).] At places the Rock Lake is missing, and the overlying limestone member (South Bend) rests directly upon the Stoner with a sharp contact. Within the major channel in Woodson County, however, the Rock Lake occurs as channel fill as much as 70 feet thick and consisting of reddish-brown weathering, friable quartz sandstone interbedded with subordinate gray shale. Exposures of the Rock Lake in this channel have been mapped previously as post-Stanton Weston Shale (Wagner, 1961) and Stranger Formation (Geologic Map of Kansas, 1964), although Miller (1969, p. 16) identified the sandstone exposures in westernmost Allen County correctly as Rock Lake. Within the major channel in Wilson County and associated minor channels cutting into the Stoner mound, the Rock Lake appears as a few to perhaps 10 feet of reddish-brown weathering, cross-bedded, friable quartz sandstone. An undetermined but substantial thickness of more massive reddish-brown sandstone exposed over about 1 square mile northeast of Elk City in northern Montgomery County also belongs in the Rock Lake. At the standard section (Fig. 3B) the Rock Lake consists of about 2 feet of unfossiliferous blocky gray shale overlain by 1.5 feet of laminated buff sandy shale and lenticular quartz sandstone carrying scattered pelmatozoan fragments.

South Bend Limestone Member

The uppermost member of the Stanton is the South Bend Limestone, formerly known in Kansas as the Kaw (Newell, 1933) and the Little Kaw (Moore, 1936). Characteristic of the South Bend is a twofold lithologic subdivision, which is recognizable along most of the Kansas outcrop and greatly aids in distinguishing this member from those below. The upper part is a relatively uniform, dark-brown to bluish-gray, medium to thick even-bedded skeletal calcilutite which contains a marine biota of fusulinids, echinoderms, brachiopods, bryozoans, molluscs, and scattered corals; algae are rare. The lower part is heterogeneous, ranging from hard, calcareous, coarse quartz sandstone and sandy calcilutite to cross-bedded oolite and conglomerate that contains calcilutite and shale pebbles in a quartz sandy matrix. The brachiopod Meekella and large pelecypods are locally common in this part.

Thickness of the South Bend is 4 to 5 feet in northeastern Kansas and changes little southward across most of the algal-mound facies belt from Anderson through Wilson counties. The upper part remains a nearly constant 2 to 4 feet of calcilutite the entire distance from northeastern Kansas, whereas the heterogeneous lower part ranges from missing in places to several feet of the various sandy, oolitic and conglomeratic rock types. Tracing of the distinctive thin South Bend over the top of the thick sandstone and shale sequence in the Woodson County channel allowed assignment of this channel fill to the Rock Lake Member. In the Wilson County channel where less Rock Lake is developed, however, the South Bend provides fill, as much as 15 feet thick, of fossiliferous, cross-bedded, conglomeratic, calcareous gray quartz sandstone with locally well-preserved trace fossils.

Only in northern Montgomery County does the South Bend thicken into a buildup characteristic of the algal-mound facies belt. At the standard section (Fig. 3B), the member is 20 feet thick with 5 feet of oolitic quartz sandstone and sandy calcilutite in the base; derbyid and productid brachiopods and crinoid columnals are locally common in this part. The upper part is 15 feet of thick-bedded calcilutite with invertebrates and phylloid algae. Westward along the Elk River Valley, this portion thickens to at least 26 feet and becomes more algae-rich with local zones of crinoidal calcarenite.

The basal contact of the South Bend is sharp over shale of the Rock Lake (or limestone of the Stoner), but locally seems transitional downward from hard calcareous sandstone to friable, less calcareous sandstone of the Rock Lake. The upper contact of the South Bend is sharp nearly everywhere with unfossiliferous buff to gray shale of the overlying Weston Member of the Stranger Formation. At places in northeastern Kansas, the upper contact is erosional beneath another member of the Stranger, the Tonganoxie Sandstone. Similar post-Stanton erosion is not observed to affect the South Bend in southeastern Kansas, however.

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Kansas Geological Survey, Geology
Placed on web Jan. 20, 2009; originally published May 1975.
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