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Owl Creek (Upper Cretaceous) fossils from Crowleys Ridge, southeastern Missouri

1955; United States Government Publishing Office; Linguagem: Inglês

10.3133/pp274e

2330-7102

L. W. Stephenson,

Paleontology and Stratigraphy of Fossils

The Owl Creek formation, which is typically developed in Tippah County, Miss., is now known to extend northward to the head of the Mississippi Embayment in southeastern Missouri.The formation is represented in Crowleys Ridge in Stoddard and Scott Counties, Mo., by 11 feet or less of weathered, mottled, yellowish-brown and greenish-gray, glauconitic, finely micaceous sand or sandy clay, indurated in part to ferruginous, argillaceous sandstone.In Missouri the formation is unconformably underlain by the McNairy sand (Upper Cretaceous), and is unconformably overlain by the Clayton formation (Paleocene).Fossils, mainly mollusks, are contained in the Owl Creek formation of Missouri in greater or less abundance; they are in the form of internal and external molds only; no shell material has escaped solution and removal by circulating ground waters, but many of the molds are identifiable.Fifty-six species are identified and described in this paper.All of them occur also in the typical Owl Creek formation of Mississippi, where their shells have been more or less completely preserved, some in almost as perfect condition as the shells on a modern ocean beach.In describing the Missouri specimens it has seemed desirable in order to present their characteristic features more clearly, to include supplementary illustrations of the more perfect shells of the same species from Mississippi.Four new genera and nine new species are described.Although these new forms are present as molds in Missouri the holotypes and some of the paratypes are selected from among the more perfect Mississippi shells.For the 4 new genera, including 1 pelecypod and 3 gastropods, the names Tenuipteria, Trobus, Eoharpa and Eoacteon are proposed ; the new species are the pelecypods Crenella microstriata, Cardium (Oranooardium) lowei and Tellina buboana, and the gastropods Pseudomalaxis pateriformis, Trobus buboanus, Helicaulax formosa, Morea transenna, Liopeplum rugosum, and Eoharpa sinuosa.The Owl Creek formation is the youngest and stratigraphically the highest Upper Cretaceous formation present in outcrop in the eastern Gulf region.In terms of the European classification the formation falls within the Maestrichtian stage (upper part of Upper Cretaceous).SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY Strata presumed to be of Ripley (Late Cretaceous) age were known and mapped to the extreme head of the Gulf Embayment in southern Illinois as early as 1906, but no fossils were discovered in them and they were considered to be of nonmarine origin (Glenn, 1906, p. 27-29, pi. 1).More recent investigations have failed to disclose fossils in these beds in Illinois on which to base a correlation, but the geographic and stratigraphic relationship of the beds with reference to other known formations indicate that they are the northern extension of the McNairy sand member of the Eipley formation of Tennessee and Kentucky.Lamar and Sutton (1930, p. 853-854, fig. 1) state that the Ripley of southern Illinois is unconformably overlain by the Porters Creek clay.He did not recognize the Clay ton formation (Paleocene) between the Ripley and the Porters Creek.At the old Olmstead ferry landing the Porters Creek clay is 60 or TO feet thick; the upper 30 feet is mined as fuller's earth.Lamar reports indistinct imprints of marine fossils that are too poorly preserved for identification in the fuller's earth in Illinois.I visited the Olmstead locality in 1936 and found paleontologic evidence in a small, poor exposure along an old abandoned road about 100 yards upstream from the old Olmstead ferry landing that the Clayton formation is present beneath the Porters Creek clay.The section here is as follows:Section along an old abandoned road 100 yards from the old Olmstead ferry landing, PulasJci County, III.Paleocene series: Clayton formation: Feet Sand, greenish-gray argillaceous, richly glataco-nitic__________________________ 2 Sand, weathered brown, ferruginous, argillaceous,, glauconitic, with many chert pebbles in lower 18 inches; contains poorly preserved prints of fossils in lower 2 feet; recognized Venericardia sp.(of the V. planicosta group), Idonearca saffordi (Gabb), Turritella sp___ 4 l/2 Unconformity.Upper Cretaceous series:McNairy sand: Sand, fine white micaceous____________ 2 Concealed to water level___________________40±The position of the preceding section is stratigraphically below the Porters Creek clay, and the recognized fauna in the glauconitic sand is sufficient to identify the Clayton formation.In a later visit to the Olmstead locality when the Ohio River was at flood stage several poor exposures of the richly glauconitic sand of the Clayton formation were seen in the immediate vicinity of the old ferry landing, but no additional fossils were found.Prior to 1932 neither the Clayton formation nor the Porters Creek clay were known west of southern Illinois in southeastern Missouri; however, prophetic of their discovery Lamar and Sutton (1930, p. 853) said:West from Pulaski County, Illinois, the formation dips below younger sediments and is not known to occur elsewhere at the surface, unless the gray clay reported at Idalia and Bloomfield, Missouri, is Porters Creek-a conclusion which a study of well records of the region seems to justify.Lamar and Sutton also stated (p.855-856) :Clays ascribed to the Lagrange, probably either the lower part or the dark gray upper phase described later, are also exposed near Idalia and Bloomfield, Missouri, in Crowleys Ridge.These clays have been called the Idalia shale by Marbut [1902, p. 21-23], who describes the clays as "uniformly dark in color and, where freshly exposed, it is black, very much resembling the dark shales of the Coal Measures".About 60 feet of this clay is exposed near IdWia, * * *.As previously stated, it is thought that the gray clay exposed at Idalia and Bloomfield may be the upper part of the Porters Creek formation instead of one of the Lagrange clays.X X