Abstract

The area of study includes Hockley, Lubbock, Crosby, Terry, Lynn, and Garza Counties. The Leonard Series is the second of four series in the Permian System. It is composed of a regressive sequence of prograding, shelf-edge barrier reefs which separate a shelf facies from a basin facies. The shelf facies is bedded carbonates intercalated with light-colored shales and anhydrite. The basin facies is dark shales and argillaceous limestones. The reefs are usually massive dolomite. The oldest Leonardian deposit is the Wichita (Abo) Formation. There is an upper and a lower reef cycle within the Wichita Formation. The Wichita Formation is overlain by the lower Clear Fork Formation which has no mappable basinal facies. The lower Clear Fork is overlain by the Tubb Sandstone on the shelf and its basinal equivalent, the Dean Sandstone. The Dean Sandstone is the basinal equivalent of both the lower Clear Fork Formation and the Tubb Sandstone. This relationship is apparent at the north end of the Midland basin because the shelf edges are separated horizontally by progradation and depositional topography is minimized. The Tubb and Dean Sandstones are overlain by the middle Clear Fork Formation. It is overlain by the upper Clear Fork Formation and the Glorieta Sandstone. The basinal equivalent of these is the Spraberry Formation. The Glorieta and upper Spraberry sandstones are overlain by the San Andres Formation which may be in part or all Leonardian. The upper boundary of the Leonard Series is problematical.