Latest Devonian–Earliest Mississippian nearshore trace-fossil assemblages from West Virginia, Pennsylvania, and Maryland

Abstract

Trace fossils are used in deposystem analysis of Late Devonian–Early Mississippian nearshore facies in the north-central Appalachian Basin. These nearshore facies resulted from separate transgressions during latest Devonian (Cleveland Shale) and earliest Mississippian (Sunbury Shale) time. Emphasis is placed on a well-exposed section at Rowlesburg, West Virginia, where the Oswayo, Cussewago Sandstone, and Riddlesburg Shale Members of the Price Formation are exposed.The Oswayo Member at Rowlesburg preserves an offshore-to-lower shoreface transition in a complex of euryhaline, protected-bay, lagoon, and possible estuarine facies. Cruziana is common and occurs along with Arthrophycus, Bifungites, Chondrites, Planolites, Palaeophycus, Rhizocorallium, Rosselia, Rusophycus, and Skolithos in intensely bioturbated mudstone, siltstone, and sandstone. These lithologies were deposited below fair-weather wave base and grade upsection to upper shoreface facies comprised of thick, horizontally-laminated sandstones with thinner, burrowed mudstone interbeds. Upper shoreface traces consist of Arenicolites, Cruziana, Diplocraterion, Dimorphichnus, Planolites, Thalassinoides, and Skolithos. Skolithos “pipe rock” sandstones occur at the toe of upper shoreface facies. Eastward the Oswayo Member grades into a restricted-bay facies and finally into beach and tidal flat facies near its stratigraphic wedge-out in eastern West Virginia and western Maryland. The Cussewago Sandstone Member at Rowlesburg overlies the Oswayo and is bounded at the top by a disconformity. The Cussewago contains Arenicolites, Isopodichnus, Phycodes, Planolites, and Skolithos in upper shoreface sandstones possibly related to deposition in deltaic or tidal channel systems.Regionally, the Riddlesburg Shale records a range of euryhaline environments in shallow-shelf, open-bay, and probable estuarine facies. The Riddlesburg Shale Member at Rowlesburg is comprised of dark-grey silty shales, siltstones, and hummocky cross-stratified sandstones. Trace fossils include Bergaueria, Bifungites, Fustiglyphus?, Helminthopsis, Planolites, and Skolithos. Lithofacies of the Riddlesburg Shale in West Virginia were markedly influenced by a syndepositionally active basement feature, the West Virginia Dome. Riddlesburg-age shoreface sandstones deposited on the crest of the Dome contain apparent omission surfaces with common Rhizocorallium and Arenicolites, Cruziana?, Planolites, and Skolithos.

A New Ichnospecies ofArthrophycusfrom the Late Carboniferous (Pennsylvanian) of Michigan, USA

“…We agree with Mángano et al (2005) that the Kentucky and Spain reports are highly questionable, but the specimens described by Bjerstedt (1987) and Turner and Benton (1983) possess the essential morphological features widely attributed to Arthrophycus (Table 1) and should not be excluded from the ichnogenus on the basis of stratigraphic age. A. parallelus n.isp.…”

Devonian fish remains from the Dulcie Sandstone and Cravens Peak Beds, Georgina Basin, central Australia

“…Possibly these burrowed horizons represent the trace fossil Skolithos, which if confirmed would represent evidence of a marine influence (this trace fossil is generally considered to indicate shallow marine conditions; e.g. Seilacher 1967Seilacher , 1978Frey 1978, Bjerstedt 1987.…”

A note on the occurrence of Arthrophycus in the Bell Island Group of eastern Newfoundland

“…In the above mentioned coeval sequences, this ichnogenus occurs in Spain, Portugal, Brittany, Morocco and Argentina and typically in abundant and monospecific and gregarious populations pre served in convex relief on sandstone soles. Indeed, preservation as isolated specimens such as that described here is not common place, though, for example, Ksiazkiewicz (1977), Legg (1985), Durand (1985) and Bjerstedt (1987) have described similar examples. Such occurrences as isolated individuals are, how ever, atypical and not clearly understood.…”

“…4, figs. 3 ,4 ;Bjerstedt, 1987, fig. 8.1, p. 876) have identified the ichnogenus based on single, commonly incomplete burrows that exhibit neither bunch ing nor the central furrow.…”