Petan Basalt mapped widely in report area--present in the southeastern part of sheet, and southern part of the Sierra Vieja, Presidio Co, TX, Permian basin. Present also southwest of the Davis Mountains, Jeff Davis Co. [Author states that correlation of volcanic rocks from area to area on Marfa sheet is uncertain--little attempt is made to correlate between areas. The rocks are described by area.] Consists of trachyandesite porphyry, dark greenish gray to brownish gray. Thickness is as much as 510 ft. Includes Bell Valley Andesite of the Wylie Mountains area (Culberson Co) and the Jones Formation of the southern Davis Mountains. Petan is mapped alone in all areas except the Eagle, Van Horn, and Wylie Mountains--in those areas it is shown on the Correlation of Map Units as a formation of Garren Group, which consists of (ascending): Hogeye Tuff, Pantera Trachyte, an undivided part, and Petan Basalt. Of Oligocene age. Geologic map.

Source: GNU records (USGS DDS-6; Denver GNULEX).