This study focuses on coastal incised valleys developed in fluvio-deltaic successions during icehouse times, generally considered as the expression of high-frequency base level variations driven by glacioeustatism. Geometry, dimensions and architecture of such incised valleys are tightly controlled by compounded factors, including rate and duration of base-level change, sediment supply, fluvial and marine processes as well as strata incised. Fluvio-deltaic successions of the Late Carboniferous exhibit complex facies and architectural variability at the scale of meters to a few tens of meters, considered as the expression of frequent and repeated changes in base-level, forcing temporal changes in deposystem dynamics, thus prone to incised valleys development. Throughout three Formations of the Breathitt Group, incised-valley fills were identified and characterised in order to better understand processes of formation and infill, lateral connectivity as well as stratigraphic stacking patterns and vertical amalgamation potential.