The Pennsylvanian Pikeville, Hyden and Four Corners formations of the Breathitt Group in eastern Kentucky, USA, contain six major facies associations along with a number of subassociations. These facies associations are offshore siltstone, rhythmically bedded mouthbar heteroliths, predominantly fine-grained floodplain deposits, minor channel fills, major distributary channels and major, stacked fluvial bodies. The stacked fluvial bodies are incised into a variety of open marine and delta plain deposits, have widths of several kilometres and exhibit a range of sandy fill types. These fluvial complexes are interpreted as incised valley fills.Parasequences and parasequence sets are not identifiable. Nonetheless, it is possible to identify systems tracts on the basis of sequential position, facies associations and systematic changes in architectural style and sediment body geometries. The studied portion of the Breathitt Group comprises stacked 4th-order sequences, which occur in lowstand, transgressive and highstand sequence sets related to the development of a lower frequency base level cycle.In the lowstand sequence set, incision associated with successive 4th-order sequence boundaries has commonly removed all the HST and TST of the underlying sequences, such that succeeding 4th-order incised valley fills are amalgamated. Within the transgressive sequence set, incision is at a minimum and incised valley fills tend to stack discretely with the maximum amount of fine-grained TST and HST between them. The highstand sequence set is transitional between the lowstand and transgressive sequence sets in terms of the amount of transgressive and highstand deposits preserved. Incised valley fills tend to stack discretely.

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Advances in the understanding of coal depositional environments have led to the notion that thick, low ash deposits in close proximity to siliciclastic sediment inputs are most commonly restricted to the products of raised mires. These mires are initiated, sustained and preserved in conditions of slowly rising base level (relative sea-level). Hence it is possible to consider the stratigraphic significance of economic coal seams within the concept of unconformity bounded depositional sequences (sensu Vail et al.). Time-equivalent clastic deposits tend to be minor (commonly with a heterolith fill) channel deposits, with brackish to freshwater lake and crevasse splay sediments, excluded from the peat mire either via the topographically raised nature of the mire or by the landward dislocation of fluvial facies. In this paradigm, spatially related major fluvial channel deposits, major seam splits and even washout deposits may not be time-equivalent to the coal seam. Regional correlations suggest that thick coal seams are time-correlative to significant flooding surfaces at the coeval coastline. Thus coals may be correlated with initial flooding surfaces over incised valley systems and sometimes with parasequence and parasequence set boundaries. This factor may be important in coal exploration. Application of these ideas to the classic Westphalian 'Coal Measures' of England indicates that the 'marine bands' may be regarded as flooding surfaces or condensed sections, with several being good candidates for maximum flooding surfaces. Between these marine bands the stratigraphy is punctuated by thick, stacked, regionally extensive fluvial units, incised into previously deposited sediments. These are interpreted as incised valley complexes. Systems tract assignment, based on changing accommodation space, indicates that the main coal zones fall dominantly within transgressive systems tracts. Depositional modelling of coal-bearing strata was largely initiated by work in the Carboniferous coal fields of the Central Appalachian Basin (e.g. Home et al. 1978; Howell & Ferm 1980). These models assumed that the nature of coal deposits (thickness, lateral extent, ash content and quality) was controlled by the autocyclicity of clastic environments which surrounded the peat-forming environments. Horne et al. (1978)

Interfluvial sequence boundaries are a largely neglected aspect of sequence stratigraphy. They are subtle lowstand exposure surfaces which in marginal and nonmarine environments are often difficult to distinguish from exposure surfaces developed during the transgressive and highstand systems tracts. Three examples of interfluvial sequence boundaries, correlated with incised valley fills along strike, are described from Pennsylvanian delta plain deposits of the Breathitt Group of eastern Kentucky. The most common interfluvial palaeosols in the Breathitt Group are gleys developed under poorly drained conditions. This is in contrast to much of the published literature which suggests that soils on interfluves ought to be freely drained. Previously published geochemical analyses suggest that interfluvial palaeosols within the Breathitt Group are composite, forming initially under freely drained conditions and subsequently becoming gleyed due to a rise in the water table during the late lowstand and early transgressive systems tracts. This is a good criterion for differentiating lowstand palaeosols from those developed during the transgressive and highstand systems tracts. Interfluvial sequence boundaries in the Breathitt Group have low preservation potential, being readily eroded by fluvial activity in the transgressive systems tract, which may totally remove all evidence of their former existence. In addition, if incised valleys overspill their margins during major flood events, interfluves may be represented by aggradational successions comprising thin coal seams, rootlet horizons and mature palaeoforests interbedded with crevasse splay sandstone. In such circumstances the presence of an interfluve can only be determined by the presence of correlative incised valley fills along strike.

Synopsis Detailed sedimentological investigations in the Don Valley, Grampian Region, have allowed the subdivision of the outwash succession into four main lithofacies associations, namely proximal braided outwash, distal braided outwash, overbank deposits and distal alluvial fan deposits. In addition two types of diamicton have been identified; firstly, basal diamicton sheets which mantle bedrock and are interpreted as probable lodgement tills and, secondly, more localised diamictons capping and interbedded with the outwash deposits, which are interpreted as debris flows from ice (‘flow tills’). Many of these successions display deformation features and faulting as a probable consequence of deposition on top of and banked against stagnant ice. This provides evidence for the style of deglaciation of the Don Valley which was by stagnation and in situ melting rather than by active retreat.