The Mescal quadrangle straddles the divide between the Tucson basin to the west and the San Pedro Basin to the east. The region is dominated by Late Tertiary basin-fill deposits that form the low divide between the Whetstone Mountains to the south and the Rincon and Little Rincon Mountains to the north. Interstate 10 crosses this low area just south of the drainage divide. The Mescal 7.5´ quadrangle was mapped as part of the STATEMAP program. Fieldwork was carried out between November, 2000 and April, 2001 and was concurrent with mapping to the north in the Galleta Flat 7.5´ quadrangle. The low, subdued nature of the area hides a complex geologic history. Shallowwater platform carbonate and mature clastic sedimentary rocks were deposited during the Paleozoic on an extensive erosion surface beveled across Proterozoic granitic and metamorphic rocks. Erosion and faulting during the Late Jurassic led to infilling of the Bisbee Basin by the upper Jurassic to middle Cretaceous Bisbee Group. The resulting succession of Paleozoic and Mesozoic strata in the Whetstone Mountains is one of the thickest sequences preserved anywhere in the state. These rocks were deformed during compression and thrust faulting during the Laramide orogeny at the end of the Cretaceous. Laramide structures are now obscure because of overprinting by younger deformation, plutonism, and extensional. The region owes its present geography to younger (Miocene) block-faulting that occurred during Basin-and-Range extension. Late Tertiary (Late Miocene to Pliocene) sediments partially filled the low areas, and these deposits have been modified by repeated cycles of dissection and deposition during the Quaternary.