The later Paleozoic systems are exposed in several disconnected areas in trans-Pecos Texas, including the Marathon region, the Delaware-Guadalupe Mountains, and the Diablo Plateau. The Carboniferous of the Marathon Basin is nearly 8,000 feet in thickness and consists mostly of clastic sediments. On the northwest these give place to limestones, which are best exposed in the Hueco Mountains, where they are about 2,000 feet thick. These beds are separated from the overlying Permian in all of trans-Pecos Texas by a notable structural unconformity. In the Glass Mountains and Delaware-Guadalupe Mountains the Permian is represented by normal marine deposits whose rich and varied faunas refute the common notion of a general impoverishment of Permian life. These pass laterally int rocks of different facies, including limestones bearing poor faunas, and deposits of red beds, salt, and anhydrite.