Facies Architecture in a Fluvial-Deltaic Sequence, Upper Crooked Fork Group (Pennsylvanian), Tennessee and Kentucky

Michael J. Barden

The upper Crooked Fork Group on the Cumberland plateau in northeastern Tennessee and southeastern Kentucky includes the Wartburg Sandstone (Corbin of Kentucky) and surrounding fine-grained strata of the Breathitt Formation below the Poplar Creek Coal. Detailed study of outcrops employs lateral profiles and architectural element analysis. Examination of bounding surfaces within and between elements indicates a sixfold hierarchy based on areal extent and geometry.

The Wartburg Sandstone consists largely of three-dimensional macroform bar complexes. Foreset macroform elements predominate, with minor lateral accretion elements present and no apparent internal cyclicity. The channelized base of the Wartburg, predominance of large-scale planar and trough cross-stratification, low paleocurrent variance, and presence of soft-sediment deformation elements and massive sandstone elements with large mudstone intraclasts suggest a low-sinuosity fluvial setting. Strata overlying the Wartburg display fine-grained lateral accretion elements and associated overbank-fines. This suggests an upward change in fluvial style in the upper Crooked Fork Group from a predominantly coarse-grained low-sinuosity setting to a fine-grained high-sinuosity setting.

The abundance of downstream and lateral accretion elements, plant debris, rooting, and thin discontinuous coals; paucity of burrows and bioturbation; and presence of thin marine horizons combined with the facies architecture suggest a channelized depositional setting with some marine influence, indicative of fluvial or fluvial-dominated deltaic deposits.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.