Trace fossils from marginal marine facies of the Kanawha Formation (Middle Pennsylvanian), West Virginia

Abstract

Seven sedimentary facies have been identified in a 40-m-thick portion of the Kanawha Formation near Chelyan in southern West Virginia. Lithology, sedimentary and biogenic structures, body fossils, paleocurrent patterns, and facies geometry have been used to identify the following paleoenvironments: Facies 1, fluviodeltaic channels represented by thick, cross-stratified channel sandstone; Facies 2, crevasse splays and tidal creeks represented by thin, cross-stratified wedge and channel sandstone; Facies 3, coastal swamps and lakes represented by coal seat and carbonaceous shale; Facies 4, restricted bay and upper tidal flats represented by dark-gray shale, mudstone; Facies 5, interdistributary bays represented by olive-gray siltstone and shale with brachiopods; Facies 6, bay or tidal flat scour fills represented by sandy limestone with brachiopods and pelmatozoans; and Facies 7, low to mid tidal flats and distributary mouth bars represented by thinly interbedded, rippled sandstone and siltstone.Trace fossils representing 17 ichnogenera are present with most being restricted to certain sedimentary facies. Three ichnoassemblages are recognized. 1) An annulated vertical burrow assemblage, consisting of arthropod(?) dwellings, occurs in an abandoned fluvial channel facies. 2) APhycodes–Zoophycosassemblage is associated with dark-gray shales and mudstones of a restricted bay and/or upper tidal flat environment. Additional ichnogenera includePlanolitesand ?Conostichus. 3) AnOlivellitesassemblage with a high abundance and a high diversity of trace fossils occurs within a rippled sandstone/siltstone facies; trace fossils include (in order of abundance)Olivellites, Teichichnus, Planolites, Aulichnites, transversely ridged surface trails,Rosselia, Scolicia, Curvolithus, Helminthopsis, Tasmanadia, Petalichnus, Ancorichnus, and ?Asterosoma. The associated depositional environments are interpreted as low to mid tidal flats and possibly distributary mouth bars.The occurrence of salinity-sensitive trace fossils such as the assemblages described herein within otherwise faunally barren intervals facilitates the recognition of marine-influenced coastal facies in which stenohaline or brackish body fossils are lacking.