Wong, Th. E. (Ed.): Proceedings of the XVth International Congress on Carboniferous and Permian Stratigraphy. Utrecht, the Netherlands, 10–16 August 2003. Royal Netherlands Academy of Arts and Sciences Carboniferous echinoderm zonation in the Appalachian Basin, eastern USA F.R. Ettensohn 1,W.I.Ausich2,T.W.Kammer3, W.K. Johnson 1 & D.R. Chesnut, Jr. 4 1 Department of Earth & Environmental Sciences, University of Kentucky, Lexington, KY 40506, USA; e-mail: [email protected] 2 Department of Geological Sciences, Ohio State University, Columbus, OH 43210, USA 3 Department of Geology and Geography, West Virginia University, Morgantown, WV 26506, USA 4 Kentucky Geological Survey, University of Kentucky, Lexington, KY 40506, USA Abstract The Carboniferous was a period of major echinoderm evolution, especially during Mississippian (Early Car- boniferous) time when crinoids, blastoids, and echinoids increased dramatically in abundance and diversity. The high degree of structural organization and distinctive morphologies of echinoderms make them ideal zonal indicators, and for parts of the Appalachian Basin Mississippian section, they provide greater biostratigraphic resolution than do conodonts or foraminifera. The occurrence of various echinoderm groups in time and space, however, is clearly related to the tectonic and sedimentologic differentiation of the Appalachian Basin through time. By Early Mississippian time on the Laurussian continent, most echinoderms had already made the shift to clastic-rich environments, which predominated in the basin until Middle Mississippian time. Although present, well-preserved Kinderhookian, Osagean, and Meramecian echinoderms are rare in the Appalachian Basin, and most are endemic forms with little diagnostic value. Echinoderms did, however, become especially abundant in the succeeding, late Middle and early Late Mississippian (Late Meramecian–Middle Chesterian), carbonate-rich seas, and it is for this time interval that biostratigraphic resolution, based especially on crinoids and blastoids, is best. By latest Mississippian (Late Chesterian) time, an influx of marginal-marine and terrestrial clastics flooded the Appalachian Basin and continued through Pennsylvanian time. Rare echinoderms are present in these Upper Chesterian and Pennsylvanian rocks and are sufficiently diagnostic to distinguish Mississippian and Pennsylvanian systems; however, the forms are too long ranging to provide smaller scale zonation. Based on a detailed literature search, a chart showing the ranges of diagnostic and relatively common echinoderms throughout the Appalachian Basin is presented. Keywords: Carboniferous, echinoderm, biostratigraphy, Appalachian Basin, eastern United States. Introduction and background the last tectophase of which began at the Devonian- Mississippian transition (Ettensohn et al., 2002), The Appalachian Basin is an area of complex sedi- whereas the Late Carboniferous or Pennsylvanian mentologic, stratigraphic and faunal relationships that form of the basin largely reflects subsidence ac- reflect its formation as a composite foreland basin companying the Pennsylvanian-Permian Alleghanian during several, Paleozoic, craton-margin orogenies in orogeny. As for paleogeography and paleoclimate, varying paleogeographic and paleoclimatic settings, during Early and Middle Mississippian (Tournaisian– and it is in this context that Appalachian, Carbonif- Visean) time, the basin was present on the eastern erous echinoderm faunas must be considered. The margin of Laurussia in the warm, subtropical, trade- Early Carboniferous or Mississippian form of the wind belt at 5–10◦ south latitude (Scotese, 1998), basin was largely related to the Acadian orogeny, where echinoderms and other organisms flourished. F.R. Ettensohn et al. 177 By latest Mississippian (Serpukhovian) time, how- North America was by Stuart Weller (1926), who used ever, the Appalachian basin had moved into the hu- crinoids and blastoids as the basis for five of his 14 mid, tropical, equatorial zone, and clastic sediments Mississippian zones. The zones, however, were largely associated with Acadian relaxation and Alleghanian restricted to the type Mississippian section of the Illi- compression flooded the basin; hence, marine or- nois or Eastern Interior Basin and became the basis ganisms of all sorts became comparatively uncom- for even more detailed zonation in Osagean (Upper mon. By latest Early Pennsylvanian (Late Bashkirian) Tournaisian–Lower Visean) parts of the section using time, moreover, convergence between Gondwana and camerate crinoids (e.g., Laudon, 1931, 1933, 1948, Laurussia had generated the Pangean superconti- 1973). Other echinoderm-based zones were added by nent, and the basin became isolated (e.g., Ziegler, Weller et al. (1948), and some of the more prominent 1989) with only sporadic access to open-marine wa- zones were carried into the Appalachian Basin (e.g., ters from the south or west during glacio-eustatic Cooper, 1948). Even at present, however, use of these highstands. During much of Mississippian time in the zones in the Appalachian Basin has not been well cor- basin, the major response to Gondwanan glaciation roborated with biostratigraphy based on other groups was a subtle fourth-order cyclicity in the predom- of organisms. inantly shallow-water carbonates (e.g., Al-Tawil & The Carboniferous section in the Appalachian Read, 2003), but during Pennsylvanian time, when Basin is lithologically diverse and variable, but the marginal-marine and terrestrial environments pre- rocks can generally be divided into a three-part litho- dominated, the highstand parts of these cycles gen- logic succession, including Lower and Middle Mis- erated thin, but widespread, marine zones (Chesnut, sissippian (Tournaisian–Lower Visean) clastics, Mid- 1994) in which nearly all marine life was concentrated. dle to Upper Mississippian (Upper Visean) carbon- The effects of such tectonism and cyclicity, however, ates, and Upper Mississippian through Pennsylvanian were not limited to the Appalachian Basin, for the (Upper Visean–Gzelian) clastics (Ettensohn et al., Carboniferous was a time of global tectonism related 2002). Although echinoderms have been reported to the ongoing formation of Pangea. from nearly every part of the Appalachian section, Even though the Carboniferous Period was tecton- they are clearly most abundant and diverse in Middle ically active, or perhaps because of it, many echin- and Upper Mississippian carbonates, and they decline oderm groups experienced a major expansion in di- markedly in both abundance and diversity in upper- versity and abundance, while some previously im- most Mississippian and Pennsylvanian parts of the portant groups like the corals and trilobites under- section. Part of this pattern of diversity and abun- went major decline. In fact, no period in earth his- dance may be related to the widespread distribution tory compares to Mississippian time for diversity and of shallow, open-marine, carbonate environments that abundance of echinoderm remains. The echinoderm apparently accompanied bulge uplift and moveout classes Crinoidea and Blastoidea attained their peak during Middle to Late Mississippian phases of Aca- abundances during this time, and echinoids became dian and Ouachita orogeny (Ettensohn, 1993, 1994; locally abundant for the first time in the Appalachian Ettensohn and Pashin, 1993), but factors such as pre- Basin. Crinoid remains, in particular, are so abundant dation, siliciclastic tolerance and current-energy pref- in many limestones of the period, that the Missis- erence were also important (Kammer & Ausich, 1987; sippian has been called the “Age of Crinoids,” and Waters & Maples, 1991). regional encrinites are so extensive, especially during The role of depositional facies is of particular sig- Early and Middle Mississippian time, that entire shelf nificance in the evolution of echinoderms. Early Mis- areas must have been dominated by crinoids (Ausich, sissippian echinoderms were especially well adapted 1997). to carbonate environments, as epitomized by the di- Despite the diversity of form exhibited by various verse and abundant crinoid and blastoid faunas of echinoderm classes, echinoderms are among the best the Hampton, Gilmore City, Burlington, and Keokuk characterized and most easily recognized of the inver- limestones of the Illinois Basin (Bassler & Moodey, tebrate phyla. They are also relatively abundant and 1943). However, during Early Mississippian time, un- exhibit a high degree of structural organization and doubtedly as a response to environmental changes, distinctive morphological features that make them po- echinoderm faunas evolved diverse and abundant tentially diagnostic zonal fossils (Moore, 1948). Al- communities in siliciclastic facies, such as the late though the restricted ranges of some U.S. echino- Osagean faunas of the Borden Group at Crawfordsville, derm species were noted very early by Lyon (1857) Indiana (Van Sant & Lane, 1964; Lane, 1973). The and Lyon & Casseday (1860), the first formal use of Appalachian Basin faunas are significant because they echinoderms for zonation of Carboniferous rocks in record the earliest known Mississippian faunas to 178 Carboniferous echinoderm zonation in the Appalachian Basin, eastern USA make this shift from carbonates to clastics, including marginal-marine clastics in which faunas are relatively those in the Cuyahoga Formation of northeastern and uncommon. southern Ohio (Hall & Whitfield, 1875; Miller, 1919; Roesor, 1986) and in the Nada