HIGH RESOLUTION STRATIGRAPHY OF THE MIDDLE AND UPPER MISSISSIPPIAN CANEY SHALE (VISEAN-SERPUKHOVIAN) OF OKLAHOMA

The Mississippian Caney Shale is present in the Arbuckle Mountains, western Arkoma Basin, and the Ardmore Basin and correlates to the Barnett Shale of the Fort Worth Basin and the Fayetteville Shale of the Ozarks and northern and eastern Arkoma Basin. The Caney Shale (80-100 meters) represents the first major evidence of Carboniferous cyclical sedimentation. It conformably overlies the Osagean Weldon Limestone and consists of three subdivisions: Ahloso Member (Lower Visean), Delaware Creek Member (upper Visean) and the Sand Branch Member (Serpukhovian). The Ahloso Member is coarser-grained and consists primarily of dark grey to brown calcareous and silty shale, siltsone, and thin fossiliferous carbonate. This part of the Caney Shale is cyclic with maximum flooding corresponding to darker lithologies with minor laminar phosphate and higher gamma-ray signature. It is characterized by Gnathodus texanus conodont zone. The Delaware Creek Member consists of dark grey to olive locally silty shales that contain prominent ammonoid-bearing carbonate concretions (bullion). Maximum flooding of these cycles corresponds to darker lithologies with rare minor laminar phosphate and only slightly elevated gamma ray. The Delaware Creek contains ammonoids of the late Visean Goniatites americanus and Goniatites multiliratus zones. The Sand Branch Member is very organic-rich, black to dark gray phosphatic clay shale with highly elevated gamma ray signatures within a cyclic framework. The Sand Branch has the highest TOC values and best potential gas reserves of the Caney. This member contains the Serpukhovian ammonoid Cravenoceras-Eumorphoceras zone as well as the Gnathodus bilineatus conodont zone. The Sand Branch Member of the Caney is of identical age to the lower Fayetteville Shale of the northern Arkoma Basin. The Caney Shale is conformably overlain by the Rhoda Creek Formation (Springer), which contains the highest Mississippian and basal Pennsylvanian strata.