In the part of Northeastern Mexico that borders the Rio Grande are a number of geological structural features which may mark important oil possibilities. The Salado Arch is a prominent anticline with northwesterly axial trend, approximately 100 miles long, in Nuevo Leon and Tamaulipas. Upper Cretaceous rocks are exposed along the crest of the arch and to the west where an east-facing escarpment marks the westward dip of the beds. A few miles east of the axis of the arch and running parallel to it is a very prominent west-facing escarpment, the upper rocks of which are of Eocene age. A measured section of the latter shows a total thickness of 5,422 feet. The anticline plunges southeast and the steeper limb of the fold is on the basinward rather than the mountainward side. rospects of oil production are favorable on account of the probable occurrence within drilling distance of petroliferous formations equivalent to those of the Tampico embayment.