CHARACTERIZATION OF MUDSTONE ARCHITECTURE IN THE FORT PAYNE FORMATION (MISSISSIPPIAN): IMPLICATIONS FOR POROSITY AND PERMEABILITY

Architectural elements such as channels, levees, and lobes observed in coarse-grained systems are also present in mudstone-dominated systems. This study focuses on mudstones of the Fort Payne Formation near Celina, Tennessee. The Fort Payne was deposited during the early Mississippian on the Borden-Grainger shelf-to-slope system. Highway construction of TN-52 exposed discrete slope channels that measure ~40 m wide and incise 10-15 m into background strata. Carbonate allochems are imbricated as clasts in the channel system suggesting unidirectional flow, likely to the west-southwest. The background mudstones are both carbonate and siliciclastic, suggesting a mixed source region. Fossil fragments, such as crinoids and brachiopods as well as minerals, such as calcite, are common in the mudstones and exemplify the heterogeneities this system can have.

Within the larger slope channel sequence, mudstone micro-channels make up the bottom 5-10 m of a 100 m wide outcrop. The smallest micro-channel features measure 3 cm in height and 5 m in width; the largest micro-channels, 1 m in height and 20 m in width. Textures within the mudstone features are investigated using high-resolution measured sections, photographs, hand samples and scanning electron microscopy (SEM). In general, micro-channels are characterized by fine-grained (<62. 5μm), platy clay fabrics and imbricated mineral and fossil fragments. Stacked micro-channels are interpreted to indicate low velocity depositional events; incised micro-channels indicate higher velocity depositional events. Our results suggest that these small-scale features affect the porosity and permeability of mudstones in the Fort Payne Formation.