Rock Types Along the Arizona–New Mexico Border

The AZ–NM border region (Mogollon Rim, Four Corners, Zuni Mountains) exposes a spectacular geological cross-section:

Sedimentary (Dominant)

• Sandstone: Coconino, De Chelly, Entrada – cliff-formers, cross-bedded dunes
• Limestone: Kaibab, Redwall – fossiliferous, karst features
• Shale: Bright Angel, Mancos – slope-formers, marine mud

Volcanic

• Basalt: San Francisco Volcanic Field (AZ), Zuni-Bandera (NM) – young flows, cinder cones
• Andesite/Rhyolite: Mogollon-Datil volcanic field (Oligocene-Miocene calderas)

Metamorphic

• Gneiss/Schist: Proterozoic basement (1.7–1.6 Ga) in Mazatzal, Sierra Ancha
• Quartzite: Metamorphosed sandstone (Mazatzal Quartzite)

Igneous Intrusions

• Granite/Diorite: Laramide plutons (70–50 Ma) – mineralized (copper, molybdenum)

Why So Diverse?

Convergence of:
• Colorado Plateau (flat-lying sediments)
• Basin & Range extension
• Mogollon Rim transition zone
• Ancient suture zones (Yavapai-Mazatzal provinces)

Prime area for field geology, hiking, and mineral exploration.