Stratigraphic and sedimentologic analysis of the 'middle Bloyd' sandstone (Morrowan) in outcrops, Mount Judea & Lurton quadrangles, Newton County, northern Arkansas.

摘要

The middle Bloyd sandstone is a bluff-forming, non-marine unit within the mostly marine Bloyd Formation (Morrowan, Early Pennsylvanian) of northwest Arkansas. It was deposited on a broad braid plain and crops out in a west-east trending belt that extends from western Madison County to Newton County. The unit extends southward into the Arkoma Basin, a foreland basin associated with the Ouachita orogeny of central Arkansas.;The geometry of the unit varies significantly in southeast Newton County where six sections were measured and surveyed for sedimentary structures and thickness variations. The sedimentary structures encountered consist of trough cross bedding, planar (tabular) bedding, and ripple cross laminations. The results of the investigation suggest multiple genetic unit each representing a particular depositional event. The regional cross-section shows a thinning and thickening pattern ranging from three meters to 30 meters in thickness throughout the region which suggest two channel complexes where one or more threads of the river migrated cyclically.