LEO F. LAPORTE Dept. Geology, Brown University, Providence, R. I
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LEO F. LAPORTE Dept. Geology, Brown University, Providence, R. I. Paleoecology of the Cottonwood Limestone (Permian), Northern Mid-Continent Abstract: The Cottonwood Limestone, a thin (7 abundant, and well-preserved fauna, especially feet or less), laterally persistent, fossiliferous, marine brachiopods, molluscs, and ammodiscid foraminifers limestone and calcareous shale, has been traced in (shelly facies). At the southern limit of its outcrop outcrop from southeastern Nebraska to north- the Cottonwood Limestone is a medium crystalline central Oklahoma. Detailed field and laboratory limestone with thin, shaly layers; molluscs, Osagia, analyses reveal 5 distinct facies. From southern and quartz silt are common (silty Osagia fades). Nebraska to central Kansas the lower half of the The bioclastic and fusuline facies were deposited Cottonwood Limestone is a fine-grained buff lime- in shallow, well-lit, moderately turbulent waters stone composed of finely comminuted fossils, es- having very small amounts of terrigenous influx; pecially the algal-foraminiferal intergrowth Osagia, water circulation was variably restricted. The echinoderms, and bryozoans (biodastic facies). shelly facies was deposited in a less turbulent and The upper half of the unit in this region is fine- deeper-water environment, having good circu- grained buff limestone with abundant small fusu- lation and relatively large amounts of terrigenous lines; fossils typical of the bioclastic facies are also material entering from the south; the silty Osagia present (fusuline facies). In central Kansas the Cot- facies was formed in a shallower, more turbulent, tonwood Limestone is a fine-grained, gray, massive nearer-shore environment marginal to the shelly limestone having abundant broken thalli of the facies. Separating these two facies provinces was a calcareous alga, Anchicodium, and some Osagia broad shoal where the platy algal facies was de- (platy algal facies). The Cottonwood in southern posited; here waters were moderately turbulent, Kansas and northern Oklahoma is an mterbedded well-lit, shallow, and somewhat restricted in circu- limestone and calcareous shale with a very diverse, lation. CONTENTS Introduction 522 General statement 541 Acknowledgments 522 Field 541 Regional setting 522 Laboratory 541 Stratigraphy 522 References cited 543 Paleogeography 523 Cottonwood facies 525 Figure Bioclastic facies 525 1. Stratigraphic section of Council Grove Group . 523 Description 525 2. Paleogeography of area during deposition of Distribution 528 Beattie Limestone 524 Fusuline facies 530 3. Restored section of Cottonwood Limestone . 526 Description 530 4. Summary of thin section data 528 Distribution 530 5. Cottonwood Limestone sampling localities . 529 Platy algal facies 531 Description 531 Plate Following Distribution 531 1. Cottonwood Limestone: field ' of various Shelly facies 532 facies Description 532 2. Cottonwood Limestone: photomicrographs of Distribution 532 bioclastic and fusuline facie: Silty Osagia facies 533 3. Cottonwood Limestone: photomicrographs of •534 Description 533 platy algal, shelly, and silty Osagia facies . Distribution 533 4. Cottonwood Limestone: bedding surfaces, bur- Interpretation of facies 534 row structures, and photomicrograph of General statement 534 Osagia sp y Northern facies province 534 Southern facies province 538 Table Shelly facies 538 1. Cottonwood facies mineralogy 527 Silty Osagia facies 539 2. Summary of Cottonwood facies characteristics . 536 Summary 539 3. Summary of Cottonwood facies composition . 537 Conclusions 540 4. Environmental factors responsible for Cotton- Appendix on methods 541 wood facies differentiation 540 Geological Society of America Bulletin, v. 73, p. 521-544, 5 figs., 4 pis., May 1962 521 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/73/5/521/3442062/i0016-7606-73-5-521.pdf by guest on 01 October 2021 522 L. E. LAPORTE-PALEOECOLOGY, COTTONWOOD LIMESTONE Company read the manuscript and offered INTRODUCTION helpful comments for its improvement. This study describes the sedimentary facies within the Cottonwood Limestone and ex- REGIONAL SETTING plains them in terms of the primary deposi- tional environment. This stratigraphic unit of Stratigraphy the northern Mid-continent was selected for The Cottonwood Limestone Member is the study because: (1) the unit is thin (7 feet or lowest of three members comprising the Beattie less) and can be traced for a distance of more Limestone Formation of the Council Grove than 250 miles; (2) the line of outcrop transects Group, Wolfcampian Series, Permian System. the original sedimentary basin almost from The Cottonwood lies structurally within the shore to shore; (3) the fauna and flora are Prairie Plains Homocline (King, 1951, p. 47), fairly well-known, at least to the generic level; which strikes north from south-central Okla- (4) the physical stratigraphy has been worked homa through eastern Kansas to southeastern out in detail, permitting concentration of ef- Nebraska and dips at very low angles to the fort on facies description and analysis; (5) re- west. sults of a similar study of the two overlying The Council Grove Group (Fig. 1) consists units, the Florena Shale and Morrill Limestone of many thin, fossiliferous, marine shales and (Imbrie, 1955; Imbrie and others, 1959), pro- limestones intercalated with non-marine sand- vide additional criteria for interpreting Cot- stones and shales. The Beattie Limestone con- tonwood characteristics; (6) several facies of tains, in ascending order, the Cottonwood the Cottonwood Limestone are found through- Limestone, Florena Shale, and Morrill Lime- out upper Paleozoic cyclic deposits of the stone, fossiliferous marine shales and limestones northern Mid-continent. having an aggregate thickness of 3-24 feet. This investigation was also undertaken to Despite this relative thinness the Beattie can discover some of the ecologic controls of the be traced in outcrop from southern Nebraska major fossil taxa in this unit. A record of the to northern Oklahoma and, in the subsurface, distribution and abundance of fossils could westward to the Colorado-Kansas line (Imbrie serve as the basis for limited ecologic interpreta- and others, 1959). Immediately above and be- tion. Future studies may focus on the func- low the Beattie are variegated non-marine tional relationships of the fossils in meeting the shales, the Stearns and Eskridge which locally demands imposed by the environment, and on contain thin coal beds. This alternation of the dynamic relationships within and among marine and non-marine beds is typical of upper the various fossil communities. Paleozoic deposits of the northern Mid-con- tinent and records successive transgressions and ACKNOWLEDGMENTS regressions of late Paleozoic seas. The writer is indebted to Professors John Strata in this part of the geologic column are Imbrie and Norman D. Newell of Columbia laterally persistent and of uniform thickness. University for their guidance and encourage- Changes in thickness are gradual and system- ment. Detailed field work by J. Imbrie, L. S. atic. Individual beds within the upper Pennsyl- Kornicker, and W. G. Heaslip was most valu- vanian and lower Permian commonly exhibit able in verifying the correlation of the Cotton- contrasting facies along the line of outcrop. wood. Field assistance by E. G. Purdy is also The Cottonwood Limestone was first named appreciated. Chemical analyses were made by by Haworth and Kirk (1894, p. 112-114) the K. Kalle and W. Waugh, under the direction Cottonwood Falls Limestone from quarries of R. T. Runnels, of the Kansas Geological near Cottonwood Falls, Kansas. Prosser (1894, Survey. p. 37-41) renamed it the Cottonwood Forma- The author is grateful for the generous sup- tion and included within it the overlying port of the State Geological Survey of Kansas. shale. Later, Prosser (1902, p. 712) subdivided The National Science Foundation provided the this renamed formation into the Cottonwood writer with a Cooperative Fellowship during Limestone and Florena Shale. Condra and the summer of 1959, as well as funds (NSF Busby (1933, p. 13) formally proposed that the G-4535), which made the latter stages of Beattie Limestone Formation include the Cot- laboratory research possible. tonwood Limestone, Florena Shale, and Morrill Robert N. Ginsburg of Shell Development Limestone members. The type locality of the Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/73/5/521/3442062/i0016-7606-73-5-521.pdf by guest on 01 October 2021 REGIONAL SETTING 523 Beattie Limestone is a quarry in Beattie, seaway, the Kansas Strait, was bounded on the Kansas. northeast by a low-lying continental mass and on the west and south by tectonic lands in Paleogeography parts of Utah, Colorado, Arizona, New Paleogeography inferred for the northern Mexico, Oklahoma, and Texas. The Kansas Mid-continent region during deposition of the Strait had its principal connection with the Beattie Limestone is shown in Figure 2. An open ocean through the Arkansas Embayment elongate seaway extended from northeastern on the southeast; a lesser connection may also Wyoming, southeastward across Kansas to have existed to the southwest (Tanner, 1959). Arkansas and northeastern Oklahoma. This Lying between the Kansas Shelf Lagoon and Feet tE~7 > x — Speiser Shale -300 Funston 1 s ^fi^""— *— — Blue Rapids Sh [* L 'L i * i Grouse. Ls. ix^"^F-^3 Easly Creek Sh. V * l \Middlebura Ls. s f x— ^-x— Hooser Shale Bader Limestone T — ' * Eiss Limestone