Depositional History of the St. Joe and Boone Formations in Northern Arkansas

Journal of the Arkansas Academy of Science Volume 40 Article 22 1986 Depositional History of the St. Joe and Boone Formations in Northern Arkansas Phillip R. Shelby University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/jaas Part of the Stratigraphy Commons Recommended Citation Shelby, Phillip R. (1986) "Depositional History of the St. Joe and Boone Formations in Northern Arkansas," Journal of the Arkansas Academy of Science: Vol. 40 , Article 22. Available at: http://scholarworks.uark.edu/jaas/vol40/iss1/22 This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an authorized editor of ScholarWorks@UARK. For more information, please contact , . Journal of the Arkansas Academy of Science, Vol. 40 [1986], Art. 22 DEPOSITIONAL HISTORY OF THE ST. JOE AND BOONE FORMATIONS IN NORTHERN ARKANSAS PHILLIP R. SHELBY Department of Geology University of Arkansas Fayetteville, AR 72701 ABSTRACT The Kinderhookian-Osagean (Lower Mississippian) St. Joe and Boone Limestone represent an unconformity bounded transgressive-regressive sequence widely distributed throughout the southern midcontinent. An irregular erosional surface developed on the Chattanooga Shale (Upper Devonian) or older strata. As Mississippian Seas transgressed, they deposited a thin interval of sandstone, shale, or the two together derived from these old beds. Carbonate deposition was initiated as grain-dominated, crinozoan-bryozoan packstones and grainstones, with subordinate wackestones, and is essentially chert free. These carbonates, referred to as the St. Joe Limestone, reflect a ramp across northern Arkansas that experienced condensed sedimentation and red coloration along its conditions reflected by carbonate mudstones, very fine-grained packstones and grainstones, and penecontemperaneous chert of the overlying lower Boone Formation. The upper Boone (Burlington-Keokuk equivalents) represents a regressive sequence that returned St. Joe-type, grain-dominated, lithologies with diagenetic chert replacement to the shelf. The regression terminated in a pronounced regional unconformity overlain by Meramecian or younger strata. i INTRODUCTION DEPOSITIONAL HISTORY Kinderhookian and Osagean rocks crop out on the southwestern flank of the Ozark dome in southwestern Missouri, northern Arkansas, and northeastern Oklahoma. The St. Joe and Boone Formations (and equivalent strata) form this Lower Mississippian sequence and develop the Springfield Plateau across this area. The Lower Mississippian interval consists of an unconformity-bounded carbonate package with the St. Joe being predominantly chert-free and the Boone consisting of chert-bearing carbonates* (Fig. 1). The principal area of study include portions of northern Arkansas extending from the Oklahoma-Arkansas border eastward as far as Stone County, Arkansas (Fig. 2). A total of nine surface section localities were sampled and described from this area. Additionally, data from 159 subsurface well logs were used toconstruct an isopachous map of the Boone Formation to illustrate thickness trends throughout the region. This investigation involves a detailed petrologic study of the St. Joe-Boone interval, resulting inthe delineation of various carbonate facies which ultimately gives an insight into the depositional history of the sequence. The Kinderhookian-Osagean (Lower Mississippian) St. Joe and Boone Formations were deposited on a broad carbonate ramp designated as the Burlington Shelf by Lane (1978). Innorthern Arkansas, these formations represent deposition on a ramp at the southern edge of this shelf that extended southward into siliceous sediments of the Marat honOuachita Trough. The St. Joe and Boone Limestones represent an unconformity bounded, transgressive-regressive sequence. As Mississippian seas transgressed, an irregular erosional surface developed on rocks of Ordovician, Silurian, and Devonian age (Thompson and Fellows, 1970). The Bachelor Member of the St. Joe Formation represents the initial transgression of these seas and is generally recognized as a thin interval of greenish shale, a light-colored sandstone, or the two together derived from older strata (Post, 1982). Carbonate deposition was initiated as grain-dominated, crinozoan-bryozoan packstones, with subordinate grainstones and wackestones, and is essentially chert-free (Shanks, 1976) (Fig. 3). These carbonates, referred to as the St. Joe Limestone, were deposited in relatively shallow waters initially with gradual deepening represented by strata of the lower Boone. In some areas, this change is marked by carbonate mudstones and wackestones (Fig. 3). Inother areas, such as the Buffalo River section, it is marked by an abrupt decrease in grain-size which can be attributed to the lack of mud in the area during this time (Figs. 3, 4). Moving up through the Boone interval many surges of grain movement produce repeated cycles of carbonate strata. These cycles are reflected by repetition of grain sizes, allochemical content, and facies throughout the Boone interval (Fig. 4). However, upper Boone strata generally represent shallower water conditions than do those of the lower Boone, reflecting a regressive sequence ending with uppermost Boone deposition. This regression terminated in a pronounced regional unconformity overlain by Meramecian or younger strata. MERAMECIAN OR YOUNGER STRATA CHATTANOOGA OR . OLDER STRATA Figure 1 Stratigraphic nomenclature ofLower Mississippian rocks in Missouri, Oklahoma, and Arkansas. Shallow Versus Deep Carbonates Similar lithologies may be found in shallow and deep water settings due primarily to transportation of relatively shallow water sediments into deeper water settings. Wilson (1975) notes the documentation of several limestone turbidite facies deposited inrelatively deep water settings. However, several characteristics may be used to differentiate between shallow and deep water carbonates. Certain sedimentary structures are indicative of shallow marine settings, for example, the presence ofcurrent structures such as ripple marks and low angle trough cross stratification. Although some current structures are known from both deep and shallow environments, current activity would be much more pronounced in shallow settings, where tidal and storm activity commonly effect bottom sediments. Mudcracks are also common indicators of shallow water deposition. Character of Proceedings Arkansas Academy of Science, Vol. XXXX,1986 Published by Arkansas Academy of S (...truncated)