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Interregional correlation of the marine zones of major cyclothems between North America and eastern Europe does not support assertions that a major stratigraphic gap exists between the traditional regional Desmoinesian and Missourian stages in North America. Such a gap was previously proposed to explain an abrupt change in megafloral assemblages in the northern Appalachian Basin and by extension across all of North America. Conodont-based correlation from the essentially complete low-shelf Midcontinent succession (distal from the highstand shoreline), through the mid-shelf Illinois Basin, to the high shelf of the Appalachian Basin (proximal to highstand shoreline) demonstrates that all major -400 kyr cyclothem groupings in the Midcontinent are recognizable in the Illinois Basin. In the Appalachian Basin, however, the grouping at the base of the Missourian is represented only by paleosols and localized coal. The immediately preceding grouping was removed very locally by paleovalley incision, as is evident at the 7-11 Mine, Columbiana County, Ohio, from which the original megafloral data were derived. At the few localities where incised paleodrainage exists, there may be a gap of -1000 kyr, but a gap of no more than ~600 kyr occurs elsewhere in the Appalachian Basin at that level and its magnitude progressively decreases westward into the Illinois (-300 kyr) and Midcontinent (<200 kyr) Basins. Thus, while a gap is present near the Desmoinesian-Missourian boundary in North America, it is typically more than an order of magnitude smaller than that originally proposed and is similar to the gaps inferred at sequence boundaries between cyclothems at many horizons in the Pennsylvanian of North America.

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Early Pennsylvanian sedimentation in the Central Appalachian Basin was dominated by the successive development of south-to southwest-flowing, low-sinuosity streams in broad, longitudinal braidplains, which deposited a series of quartzarenites. Successive quartzarenite belts are locally separated by grey shales with brachiopods and other body fossils interpreted to represent marine-to brackish-water facies. Local features indicative of tidal sedimentation occur between fluvial facies and the marine-to brackish-water shales. Tidal features occur in transgressive successions between fluvial and overlying marine to brackish-water shales, and significant wave-generated features are absent, indicating that tide-dominated estuaries developed during transgressions. The boundary between fluvial facies and recognizable estuarine tidal facies represents a fluvial-estuarine transition. Tidal sedimentary features in the fluvial-estuarine transition, however, can be subtle, because upper estuarine channels may record only the most headward tidal effects in an otherwise fluvially dominated system. Some of the possible tidal indicators noted in upper estuarine channel facies include local occurrences of opposing palaeoflow indicators, noncyclic rhythmites, lenticular bedding, small reversing ripples on the crests of underlying current ripples, sigmoidal cross-strata, cross-strata with rising troughs, thick-thin laminae pairs and bundled laminae in ripple crosslamination. None of these features is diagnostic for tidal sedimentation.Where multiple tidal indicators are found within otherwise fluvial facies, within a probable transgressive succession, interpretation of an upper estuarine channel facies becomes more tenable.Recognition of fluvial-estuarine transitions is important in fluvial-dominated basins, especially in the upper reaches of longitudinal basins, because the transitions may be the only evidence of correlative down-dip marine flooding surfaces. Identification of the transition zone facilitates the distinction between lowstand and transgressive systems tracts. In turn, such sequence analyses can increase the potential for predicating lateral changes in fluvial channel continuity, and vertical changes in porosity and permeability characteristic of lithological changes from fluvial to estuarine facies, both of which are important in exploration for hydrocarbons.