The Midway sediments which cropout in northwestern Louisiana outline the highest structural portion of the Sabine uplift. They are divisible on the surface into three formations, the Naborton (oldest), the Logansport, and the Hall Summit (youngest).

End_Page 941------------------------------

Each formation is a lithologic unit which consists of a basal sand member, a middle lignitic shale member, and an upper calcareous member. The surface lithologic units can be traced locally into the subsurface by use of driller's logs and electrical logs. The practicability of employing these units for mapping is shown by the fact that detailed mapping of formations delimits the various oil fields of this area and shows the highest structural portion of the Sabine uplift to be in the DeSoto-Red River field.

End_of_Article - Last_Page 942------------