SUBSURFACE EXPRESSION OF A BRAIDED FLUVIAL TO MARINE TRANSITION IN MIDDLE MORROWAN PENNSYLVANIAN STRATA, ARKOMA BASIN OF NORTHWESTERN ARKANSAS

Morrowan rocks crop out in northern Arkansas and are displaced into the Arkoma basin by post-depositional faulting. The middle Bloyd sandstone is a bluff forming unit that crops out north of the basin dominantly as a braided stream deposit.

The middle Bloyd sandstone was defined in the basin through well log correlation, construction of cross-sections, lithologic well descriptions, and outcrop data. Regional cross-sections from mature gas fields anchored the stratigraphic succession for correlation, east across the study area into Pope County, Arkansas. Local cross sections in Johnson and Pope Counties illustrate the middle Bloyd sandstone's stratigraphic relationships and unit geometry. Changes in its lithology and character appear in outcrops and well logs as the depositional regime transitions from a braided stream deposit to a marine influenced setting.

Thickness trends were noted, allowing delineation of sediment conduits. These conduits indicate fluvial braided stream deposition, ephemeral channel migration, and marine influences.