The geographic distribution, lithology, thickness, and paleontology of the subsurface Woodford in the Permian basin are described and illustrated. On the basis of conodonts and spores, the Woodford is assigned to the Upper Devonian and correlated with the Ready Pay member of the Percha shale in New Mexico, Woodford and Chattanooga of Oklahoma, Kansas, and Arkansas, and tentatively correlated with the Upper Devonian parts of the Caballos novaculite and Arkansas novaculite of Texas and Arkansas.

The Barrilla Mountains, in the northeastern part of the Davis Mountains of Trans-Pecos Texas, are composed of Tertiary volcanic materials. Five tuffs and five lava flows, 1500 feet thick occurring throughout the mountains, persist in thickness and lithologic characteristics. Their upper surfaces show little erosion. The lavas are chiefly Silicic and soda rich. The volcanic succession is underlain by a Tertiary sandstone above Upper Cretaceous marine formations.

The magnetic iron-ore prospects of the Llano region of central Texas were investigated in a program which combined dip-needle and gravity-meter surveys by the Bureau of Economic Geology of The University of Texas and the U.S. Geological Survey with exploration by the U.S. Bureau of Mines. Magnetic observations were made on the Iron Mountain, the Bader, the Gamble, and the Olive mine prospects. Gravity observations were made over the first three areas, which subsequently were drilled. Approximately 65,000 long tons of ore is indicated for the Iron Mountain deposit.

The Barrilla Mountains, in the northeastern part of the Davis Mountains of Trans-Pecos Texas, are composed of Tertiary volcanic materials. Five tuffs and five lava flows, 1500 feet thick occurring throughout the mountains, persist in thickness and lithologic characteristics. Their upper surfaces show little erosion. The lavas are chiefly silicic and soda rich. The volcanic succession is underlain by a Tertiary sandstone above Upper Cretaceous marine formations.