The Dallas–Fort Worth Metroplex sits above Cretaceous-age strata ranging from ≈145-66 Ma (million years ago). These Cretaceous-aged sediments lie above the eroded Ouachita Mountains and the Fort Worth Basin, which was formed by the Ouachita Orogeny. Going from west to east in the DFW Metroplex and down towards the Gulf of Mexico, the strata get progressively younger. The Cretaceous sediments dip very gently (about 1°) to the east.