Kansas Geological Survey, Open-file Report 2008-15
by Robert S. Sawin and Ronald R. West
KGS Open-file Report 2008-15
This report is an expanded version of the geologic unit descriptions on the geologic map of the Tallgrass Prairie National Preserve (Sawin, 2008a); the main difference is the added fossil descriptions. Locality information (control point or 'CP' designated numbers) can be found in Sawin (2008b).
The Florence limestone caps the highest hills along the northwest edge of the preserve. Up to about 15 feet of lower Florence limestone is present. The Florence is a light-gray to yellow-gray limestone containing several nodular layers of light- to dark-gray chert. Fossils are common. As the Florence weathers, the more resistant chert accumulates on the slopes, and the hilltops become characteristically rounded.
The Matfield Shale is about 65 feet thick and is composed of three members, from top to bottom, the Blue Springs shale, the Kinney limestone, and the Wymore shale.
The Blue Springs shale is about 22 feet thick and poorly exposed. The upper part is a gray, yellow, or yellowish-green mudstone that may contain thin, discontinuous layers of limestone. Near the middle, a 1-foot bed of limestone can occur. The lower part of the Blue Springs is a varicolored (yellowish-green, green, red, and purple) mudstone (Moore et al., 1951).
The thickness of the Kinney limestone can vary in a short distance, ranging from 9 to 22 feet. The average thickness is about 16 feet. Three zones, an upper and lower limestone with a middle mudstone, are common.
The upper limestone is a gray, fine-grained skeletal limestone up to 2 feet thick. Shell fragments (<1mm) often make up almost the entire rock, giving it a grainy texture. Fossils include ostracodes (characteristic of this unit), brachiopods, high-spired gastropods, spirorbids (worm-tubes), algal blades, and crinoids. At some localities (e.g., CP-77), the skeletal fragments are almost entirely ostracodes.
The middle mudstone is gray to green and may contain one or more calcareous zones or thin limestones. Fossils are more common in the middle and upper parts (Moore et al., 1951).
The lower limestone ranges from less than a foot to over 9 feet thick. This thickening can occur within a very short distance. Where it is thicker, the light-gray to gray limestone is fossiliferous and weathers to large, elongated blocks that accumulate on the slope below the outcrop. Fossils include brachiopods (Composita sp. and Derbyia sp.), small crinoids, myalinid bivalves, and gastropods.
One outcrop (CP-75) is unlike any other exposure of the lower limestone at the preserve. The limestone here is thicker (about 9 feet) and the dip of the bedding planes is about 11 degrees. In addition, the lithology is a recrystallized gastropod coquina of alternating course- and fine-grained layers. The observed strike and dip on the bedding surfaces (N82°W, 11°N) is apparently depositional in that the Schroyer limestone, exposed in the drainage below, is relatively flat-lying. Crossbedding was not observed in these beds. Fossils are dominantly high- and low-spired gastropods with occasional myalinid bivalves (some are bored). Styolites are also common.
Reference Localities: CP-75, CP-77, CP-78, CP-114/115, CP-117
The Wymore shale is about 27 feet thick. The upper part is a light-yellowish-brown, gray, and green mudstone that contains a thin limestone; the middle is varicolored (red, purple, and green) mudstone and may contain a boxwork limestone; and the lower mudstone is gray, light yellowish brown, and yellowish green. Fossils associated with the limestone in the upper part of the Wymore include myalinid and pectinid bivalves and the brachiopod Derbyia sp.
Reference Locality: CP-114
The Wreford Limestone is composed of three members, from top to bottom, the Schroyer limestone, the Havensville shale, and the Threemile limestone. The combined thickness is about 40 feet.
The thickness of the Schroyer limestone is about 13 feet. The upper part is a massive, gray, fine-grained, recrystallized limestone with layers of chert up to 0.5 feet thick. Weathered blocks can have large vugs, and small, broken shell fragments are common. The middle part is a recrystallized, limonitic, orange-brown limestone that has a porous, clayey appearance (in some places it resembles a boxwork limestone). Fossils include algal-coated grains (approximately 4mm) and an occasional brachiopod. The lower third is a gray, fine-grained limestone containing layers of chert. The fossils are predominately echinoid spines and plates, but this limestone also contains small crinoids, fenestrate bryozoa, brachiopods (Composita sp., chonetids, marginiferid productids) in both the limestone and chert. Springs sometimes occur at the base of the Schroyer.
Reference Localities: CP-72 (Ranger's geology stop) and CP-113
The Havensville shale is about 9 feet thick. It is a light-yellowish-brown, green, and yellowish-green mudstone with interbedded (up to 2 feet) clayey, light-gray, and light-yellowish-brown limestones that are fossiliferous. Fossils are dominated by bivalves (Aviculopecten sp., Wilkingia sp., and myalinids), brachiopods (Composita sp.), and bryozoans (fenestrate and ramose); less common are echinoid spines and crinoids. At locality CP-83, the upper limestone contains silicified, articulated Composita sp. in apparent life position.
Reference Localities: CP-83, CP-111
The Threemile limestone is prominent at the preserve, forming a bench or "rimrock" of gray limestone that caps most of the flat-topped hills. The average thickness of the Threemile is 18 feet. Nodular and banded chert (chert layers can be up to 1 foot thick) is more abundant in the upper and lower parts of the unit. Chert is usually absent in the middle to upper part, and the limestone weathers to large blocks, which are sometimes vuggy. It is this part of the Threemile that forms the prominent rimrock. Thin mudstone layers may occur within the limestone. Small shell fragments (mostly crinoids, fenestrate bryozoans, and brachiopods) are common throughout the unit; near the base, well-preserved specimens include crinoids, echinoid spines and plates, fenestrate and ramose bryozoans, horn corals, and brachiopods (Neochonetes sp., Meekella sp., Wellerella sp., and productid spines). Springs are commonly associated with the Threemile.
Reference Localities: CP-110/111; CP -156, CP-242
The Speiser Shale is about 17 feet thick. The upper part is a gray to green, calcareous, fossiliferous mudstone that may contain thin limestone layers. Fossils are abundant in the upper mudstone and include crinoid columnals and cup plates, fenestrate bryozoans, brachiopods (Neochonetes sp., Chonetinella sp., Derbyia sp., and productids), and bivalves (Aviculopecten sp., Acanthopecten sp., and myalinids). The middle and lower part of the Speiser is a varicolored (red, purple, and green) mudstone.
Reference Locality: CP-110
The Funston Limestone averages about 20 feet in thickness, but varies from 15 to 24 feet and can generally be divided into an upper and lower limestone separated by a mudstone. The upper limestone contains several mudstone layers, but in general, the upper part is a light-yellowish-brown to light-gray, thin, platy limestone (rarely exposed) that contains a few broken shell fragments and algal-coated bivalves (probably permophorids), and the lower part is a gray, fossiliferous, massive limestone that commonly crops out on the hillsides, often forming a prominent bench. The lower limestone contains abundant broken shell fragments (mostly fenestrate and ramose bryozoans and productid brachipods), burrows, and bivalves (Aviculopecten sp., and Aviculopinna sp.; the latter in life position). The middle mudstone is black to dark gray. The lower limestone is very light gray to light yellow gray (sometimes nearly white), very fine grained, finely laminated, and weathers into thin plates and blocks with sharp, angular edges. Fossil occurrences vary between localities, but bivalves (Aviculopecten sp., Pseudomonotis sp., myalinids, and small algal-coated specimens) are most common. Springs from the upper and lower limestones are abundant.
Reference Localities: CP-53a/53b, CP-268a/268b
The Blue Rapids Shale varies in thickness from 14 to 24 feet, but averages about 17 feet. The gray, green, and light-yellowish-brown, calcareous mudstone may contain a thin limestone layer or boxwork limestone in the lower part of the unit.
Reference Localities: CP-53a, CP-254
The Crouse Limestone is about 11 feet thick, but ranges from 7 to 15 feet. The upper part is a yellow-gray, clayey limestone that weathers into thin plates, a characteristic of this part of the Crouse. The lower part is a gray or light-yellowish-brown, massive limestone containing siliceous nodules and geodes, iron deposits (limonite), and fossils (mostly bivalves and snails). The lower limestone is only 2 to 4 feet thick, but forms a prominent bench with large, detached blocks of limestone scattered along the outcrop. Characteristic fossils near the top of the lower limestone are high-spired gastropods and the bivalve Permophorus sp. Fossils in the lower part of the lower limestone are almost exclusively bivalves (Aviculopecten sp. and Acanthopecten sp. dominate, but myalinids and Pseudomonotis sp. are common). Springs occur at the base of the lower limestone.
Reference Localities: CP-50, CP-55, CP-91, CP-100
The thickness of the Easly Creek Shale is about 23 feet. The Easly Creek consists of an upper light-green, calcareous mudstone, a prominent limestone near the middle, and a lower varicolored (green, red, and purple), calcareous mudstone that contains a boxwork limestone near its base. The limestone, locally termed the "Easly Creek limestone," is gray, silty, and fossiliferous (algal-coated and bored bivalves and brachiopods are characteristic), and can be over 2 feet thick. The fossils are predominately brachiopods (Composita sp., Derbyia sp., and productids), bivalves (Aviculopecten sp., Acanthopecten sp., and Pseudomonotis sp.), ramose (Acanthocladia sp., and others) and fenestrate bryozoans, worm tubes (spirorbids attached to bivalve shells), and a few gastropods. The mudstone 2-3 feet above the limestone is calcareous and fossiliferous. It contains abundant broken shell fragments, crinoids, bryozoans (fenestrate and ramose), brachiopods (Composita sp., Derbyia sp., Neochonetes sp., and productids), gastropods (Straparollus [Amphiscapha] sp.), trilobites (Ditomopyge sp.), and burrows. The limestone weathers rubbly, but at some localities it is blocky and can resemble the lower limestone in the Crouse. Springs are sometimes associated with the "Easly Creek limestone."
Reference Localities: CP-32, CP-40, CP-92
The Bader Limestone is about 26 feet thick and is composed of three members, from top to bottom, the Middleburg limestone, the Hooser shale, and the Eiss limestone.
The Middleburg limestone is about 6 feet thick. It is composed of an upper limestone, middle mudstone and shale, and lower limestone. The upper limestone is gray to light gray or light yellowish brown, fossiliferous, and weathers rubbly, platy, or blocky. At some localities, this limestone is stromatolitic. Below the upper limestone is a green mudstone, and below it, a black, fissile shale. The lower limestone is light gray, massive, fossiliferous, and is usually about 3 to 4 feet thick. The fossils are dominated by bivalves (Aviculopecten sp., Acanthopecten sp., Pseudomonotis sp., myalinids), with brachiopods (productids) and less abundant gastropods (Bellerophon sp. and high-spired pseudogygoplurids). The biota, lithology, and weathering characteristics often resemble the "Easly Creek limestone." Springs sometimes flow from the Middleburg.
Reference Localities: CP-21, CP-45, CP-92
The thickness of the Hooser shale is about 5 feet. This calcareous mudstone is gray to gray green; near the base it is red.
Reference Locality: CP-92, CP-128
The Eiss limestone varies from 13 to 18 feet thick, but averages about 15 feet. It can be divided into an upper and lower limestone, and middle mudstone. The upper limestone is a massive, gray limestone that forms a prominent bench and outcrop. It is about 2 feet thick, becomes characteristically vuggy when weathered, and may contain fossils (small shell fragments) and siliceous nodules. Gypsum nodules are common in the subsurface. Springs from the upper limestone are common. The middle mudstone is gray to gray green and fossiliferous. The lower limestone is light gray, clayey, fossiliferous, and weathers rubbly. Outcrops of the middle mudstone and lower limestone are rare. Abundant fossils in the lower limestone and the lower part of the middle mudstone include brachiopods (Neochonetes sp., Meekella sp., Derbyia sp., Composita sp., Juresania sp., and Reticulatia sp.), bivalves (Aviculopecten sp., Acanthopecten sp., Pseudomonotis sp., Schizodus sp., Aviculopinna sp., and myalinids) fenestrate and ramose (Tabulipora sp., Rhombopora sp., Acanthocladia sp., and others) bryozoans, echinoid spines and plates, and crinoids (columnals, plates, and ossicles). The trilobite Ditymopyge sp. is also found.
Reference Localities: CP-17, CP-71, CP-171
The Stearns Shale is about 12 feet thick, but ranges from 8 to 14 feet. It is a varicolored (green, red, purple, and gray), calcareous mudstone that may contain thin limestone beds or boxwork limestone.
Reference Localities: CP-16/18, CP-93, CP-171
The Beattie Limestone is composed of three members, from top to bottom, the Morrill limestone, the Florena shale, and the Cottonwood limestone. The total thickness is about 21 feet.
The Morrill limestone is about 5 feet thick. It is a light-gray to yellow-brown limestone that contains thin mudstone partings. The Morrill weathers irregularly to blocky. In some areas it is massive and forms a prominent outcrop, but in other places it is inconspicuous. Fossils in the Morrill are rare except for small shell fragments near the base.
Reference Localities: CP-16/18, CP-171
The thickness of the Florena shale is about 11 feet. The Florena is a light-gray-green mudstone. The lower 3 to 6 feet are very fossiliferous (chonetid brachiopods are characteristic). Abundant fossils include brachiopods (Neochonetes sp., Meekella sp., Derbyia sp., Composita sp., and productid shell fragments), fenestrate bryozoans, echinoid spines, and crinoid columnals.
Reference Localities: CP-166a, CP-171
The Cottonwood limestone is about 5 feet thick. The fossiliferous, massive, light-gray to yellow-white limestone has a blocky appearance. Abundant wheat-grain-shaped fusulinids (Schubertella sp., Schwagerina sp., and Triticites sp.) in the upper part are characteristic of the Cottonwood; other, less common fossils include small crinoids, echinoid spines, brachiopods, ramose bryozoan, and small broken shell fragments. The lower part of the Cottonwood contains small broken shell fragments. Scattered chert nodules and thin mudstone partings may be present.
Reference Localities: CP-13, CP-159, CP-160
The Eskridge Shale is the lowermost bedrock unit exposed at the preserve, where it crops out along Fox Creek at a few localities. Maximum exposed thickness is 14 feet of light-gray-green mudstone. A thin, argillaceous limestone may occur near the middle.
Reference Locality: CP-160
The valley floor of Fox Creek and many of the narrow, upland tributaries contain floodplain and terrace deposits of gravelly silt loam and silty clay. The alluvium in Fox Creek valley is up to 35 feet thick (Mandel, 2006).
Colluvium/alluvium fans contain fine- to coarse- grained (angular chert and limestone fragments) material derived from the uplands. These deposits are up to 15 feet thick (Mandel, 2006).
Mandel, R. D., 2006, Geomorphology, Quaternary stratigraphy, and geoarcheology of Fox Creek valley, Tallgrass Prairie National Preserve, northeast Kansas: Kansas Geological Survey, Open-file Report 2006-29, 51 p. [available online]
Moore, R. C., Jewett, J. M., O'Connor, H. C., and Smith, R. K., 1951, Geology, mineral resources, and ground-water resources of Chase County, Kansas: Kansas Geological Survey, Vol. 11, 49 p. [available online]
Sawin, R. S., 2008a, Surficial geology of the Tallgrass Prairie National Preserve, Chase County, Kansas: Kansas Geological Survey, M-119A, scale 1:12,000, 1 sheet.
Sawin, R. S., 2008b, Methodology and data used to construct the surficial geology (M-119A) and water-bearing units (M-119B) maps of the Tallgrass Prairie National Preserve, Chase County, Kansas: Kansas Geological Survey, Open-file Report 2008-09, 15 p. [available online]
Kansas Geological Survey, Geology
Placed online Oct. 2, 2008
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