Transgressive channel filling in the Breathitt Formation (Upper Carboniferous), Eastern Kentucky Coal Field, USA

Carbonaceous shales of brackish or marine origin in the Breathitt Formation may exhibit sharp bases with local channel-form scours. Minor channels at the bases of these shales exhibit three general types of fill: (1) shale, (2) bioturbated, heterolithic strata, and (3) coal overlain by shale or bioturbated, heterolithic strata. Most of the scours at the bases of the channels were formed during a depositional hiatus that preceded transgression. Some may also have been formed by transgressive reworking of underlying estuarine and deltaic siliciclastics. The channel fills are bioturbated and may contain crudely cyclical rhythmites, subordinate and dominant siltstone-laminae couplets, wave ripples, and bimodal current ripple trends. The fills are interpreted to represent estuarine sedimentation during marine transgression. Channels are capped by sideritic, bioturbated sandstones that separate the fills from the overlying dark shales deposited under brackish- to marine-water conditions. Some of these sandstones may represent local transgressive surfaces. The occurrence of these types of channels in different parts of the coal-bearing Breathitt Formation supports the hypothesis of multiple transgressions during the Late Carboniferous in the Central Appalachian Basin. ?? 1992.