PROTOSALVINIA DAWSON AND ASSOCIATED CONODONTS OF THE UPPER TRACHYTERA ZONE, FAMENNIAN, UPPER DEVONIAN, IN THE EASTERN UNITED STATES

Journal of Paleontology, Jan 2009 by Over, D Jeffrey, Lazar, Remus, Baird, Gordon C, Schieber, Juergen, Ettensohn, Frank R

ABSTRACT-

Protosalvinia first occur in association with conodonts of the Upper trachytera Zone and below the Three Lick Bed in the Ohio Shale and the Ellicott Shale of the central and northern Appalachian Basin, as well as in the Clegg Creek Member of the New Albany Shale of the Illinois Basin. In the Chattanooga Shale of the southern Appalachian Basin, Protosalvinia are found no lower than the Upper marginifera Zone or associated with obviously reworked conodonts in the Middle expansa Zone. Regionally Protosalvinia are associated with a disconformity and may be found with conodonts of the Lower expansa Zone.

INTRODUCTION

PROTOSALVINIA DAWSON, 1884, also widely known by the junior synonym Foerstia White, 1923, are the remains of an enigmatic Late Devonian plant-like organism of possible terrestrial origin (Phillips et al., 1972; Gray and Boucot, 1979; Romankiw et al., 1988). The macroscopic organic remains are known from numerous localities in the eastern United States, largely from offshore marine mudrocks, in a relatively narrow stratigraphie interval (Schopf and Schwietering, 1970; Murphy, 1973; Hassenmueller et al., 1983; Conkin, 1985; Ettensohn et al., 1988). Protosalvinia has also been found in North Dakota (Holland et al., 1987), Montana (Cross, 1982, in Matthews, 1983), Oklahoma (Hass, 1956), southern Ontario (Winder, 1966) and Brazil (Dawson, 1884; Niklas et al., 1976; Loboziak et al., 1997). Hannibal (1994) noted that the carbonized cephalopod aptychus Sidetes Giebel, 1847 may have locally been misidentified as Protosalvinia. The converse is also true (see Winder, 1966), and unconfirmed reports should be considered with caution. Collections of Protosalvinia-bearing strata in New York, Pennsylvania, Ohio, Indiana, Kentucky, and Tennessee (see locality register in Appendix 1) yielded conodonts that constrain the base of the Protosalvinia Interval to no higher than the Upper trachytera Zone in the eastern United States. The lower occurrences of Protosalvinia in the rhomboidea and marginifera zones, as proposed by Sandberg et al. (1994) and proliferated by Loboziak et al. (1997), are not supported by direct conodont evidence. It is not clear if Protosalvinia associated with conodonts typical of the Lower expansa Zone are a higher occurrence or reworked.

STRATIGRAPHY

Protosalvinia in the Appalachian Basin are known from the medial Ellicott Shale Member of the Chadokoin Formation in the upper part of the Conneaut Group in New York and Pennsylvania, from the Chagrin and Huron shales in Ohio, Kentucky, and West Virginia below the Three Lick Bed of Provo et al. (1978), and from the upper Gassaway Member of the Chattanooga Shale in Kentucky, Tennessee, and Georgia (Fig. 1). In the Illinois Basin of Indiana and Kentucky, Protosalvinia are found in the lower Clegg Creek Member of the New Albany Shale. The Protosalviw'a-bearing interval is typically associated with strata in the lower part of the middle Huron Shale, just above the high gammaray interval of the lower Huron Shale and its equivalents in the Ohio, Chattanooga, New Albany, and Antrim shales (Hassenmueller et al., 1983; Ettensohn, 1992). Winder (1966), Matthews (1983), and Sandberg et al. (1994) reported Protosalvinia from the Antrim and Kettle Point formations of Michigan, Ontario, and Indiana in the Michigan Basin.

PALEONTOLOGY

Protosalvinia remains range from 1 to 20 mm in width, 5 mm being typical, characteristically flattened and often bilobed, with a reticulated cellular pattern (Fig. 2). Complete or fragmented Protosalvinia are often found in high concentration on bedding planes in marine mudrocks, but also in lag beds and shell layers. Conodonts in this study were recovered from acid residues of shell-rich layers, as well as from shale bedding plane surfaces collected from outcrops and drill cores. The conodont zonation used for the Famennian, inclusive of the Protosalvinia Interval, is the scheme proposed by Ziegler (1962a) and most recently modified by Ziegler and Sandberg (1990), which is here plotted against the Devonian radiometric time scale presented by Kaufmann (2006; Figure 1). The ranges of conodonts recovered just below or within the Protosalvinia Interval include relatively long ranging taxa such as Palmatolepis schindewolfi M�ller, 1956 and Pelekysgnathus inclinatus Thomas, 1949, but also taxa that have short ranges (e.g., Palmatolepis marginifera marginifera Helms, 1959, Palmatolepis marginifera utahensis Ziegler and Sandberg, 1984, P. glabra distorta Branson and Mehl, 1934a, and P. perlobata grossi Ziegler in Kronberg, Pilger, Scherp, and Ziegler, 1960; Fig. 3). The occurrence of Palmatolepis rugosa rugosa Branson and Mehl, 1934a from the New Albany Shale (locality A, Table 1) associated with Palmatolepis falcata (Helms, 1959), P. perlobata grossi, P. perlobata sigmoidea Ziegler, 1962b, P. glabra distorta, and Polylophodonta confluens (Ulrich and Bassler, 1926), which are not known to range into the Lower expansa Zone, may be a lower occurrence than previously reported or an indicator of the Lower expansa Zone and a reworked fauna of well-preserved older conodonts. The occurrence of Palmatolepis falcata, P. glabra distorta, and P. glabra angusta �apkinoglu, 1997 in strata above the basal Protosalvinia-beanng lag horizon that contain P. rugosa rugosa (Table 1, locality A) indicates that a lowering of the range of P. rugosa rugosa to the Upper trachytera Zone is warranted. The absence of conodonts indicative of higher zones further supports this assessment.