ABSTRACT

The Banzet Formation (Pennsylvanian System, Desmoinesian Series) consists of shales, siltstones, thin limestones, thin coals, and lenticular, discontinuous sandstones found in repetitive sequences. Analyses of sedimentary textures and structures of sandstones and of the signatures of 750 gamma-ray well logs indicate that in southeastern Kansas and northeastern Oklahoma, Banzet sedimentation consisted of southward deltaic progradation into the shallow seas that covered the Cherokee Shelf during eustatic transgressions caused by Gondwanan deglaciation.

Interpretation of prodelta and delta plain facies from gamma-ray well log signatures suggest three deltaic cycles. The first two deltaic advances were from the northeast, and covered the eastern half of the shelf. The first advance commenced after deposition of the Ardmore Limestone, and the second after deposition of the Bevier Coal unit. These deltaic cycles are characterized by distributary channel deposits up to 94 feet (21.9 meters) thick, and by widespread crevasse splay sediments. The third deltaic advance occurred after deposition of the Iron Post Coal unit, and is marked by the progradation of two delta lobes from the north. Distributary channel deposits are much thinner than those of the first two deltaic advances, and are not entrenched deeply into underlying sediments, possibly due in part to a more gentle depositional slope in the north. Subsequent marine transgression displaced the shoreline to the northeast, allowing deposition of a widespread delta-destructional sandstone in the northern half of the study area and formation of the Breezy Hill Limestone in the southern half.