The San Andres Formation is a geologic formation found in New Mexico and Texas. It contains fossils characteristic of the late Leonardian (Kungurian) Age) of the Permian Period. The formation is the most widely exposed Paleozoic formation in the state of New Mexico, cropping out in a zone 80–110 kilometers (50–68 mi) wide that extends from west Texas to central New Mexico and with additional exposures in the Zuni Mountains and Sangre de Cristo Mountains. It is also prominent in the subsurface in the San Juan Basin and in eastern New Mexico.