The Walnut Bend pool is the first major deep discovery in the Marietta-Sherman syncline, a northwest-southeast-trending feature which extends from southwestern Carter County, Oklahoma, to southeastern Grayson County, Texas, parallel with the Criner Hills axis and the Muenster arch. In this pool, 1,000 feet of Comanche rocks overlie the 4,200 feet of upper and middle Pennsylvanian (Canyon and Strawn) sediments, and beds of lower Simpson (Oil Creek) age underlie the Pennsylvanian rocks. The pre-Pennsylvanian rocks of this pool are folded into an elongate anticline. This structure was formed on an arch folded in early Pennsylvanian (pre-Bostwick) time and the Marietta-Sherman syncline was formed in late Deese time by the downwarping of the middle part of this arch. The 115 o l wells in this pool have produced more than 2 million barrels of oil from six sandstone zones between the depths of 4,100 and 5,100 feet, and a dolomite zone in the Simpson group. Occurrence of oil in the sandstone zones at 4,900 and 5,100 feet is controlled by anticlinal structure over the closely folded Ordovician beds. Electrical log cross sections are presented to indicate that oil in the 4,100-, 4,600-, and 4,700-foot zones occurs in a stratigraphic trap formed by gradation of sandstone into shale.