Basin and Range

Rocks in the Basin and Range are quite varied, containing Proterozoic metamorphic and intrusive igneous rocks and Tertiary sediments and volcanic rocks. The province is characterized by large-scale, northwest oriented fault blocks whose upthrown blocks (horsts) comprise the mountain ranges of intrusive and volcanic rocks seen today and the downthrown blocks (grabens) are the valleys between the mountain ranges. Fluvial and alluvial fan sands, conglomerates, and silts in the grabens are as thick as several thousand feet. Relatively minor amounts of Tertiary fluvial and lacustrine rocks are scattered around the fringes of these mountains. The structural geology is actually much more complicated than this simple model. This region has been the focus of much mineral extraction in the past with some gold and copper mining still occurring today.

Transition Zone

The Transition Zone in this part of Arizona is very narrow and pinches out along the Grand Wash Cliffs. The only sample collected from this zone is a finely crystalline granite from the Valentine area northeast of Kingman. The Transition Zone, which widens southeast towards Globe and Miami, marks an area of complicated structural geology that represents the adjustment boundary between the relatively low-lying Basin and Range and the rising Colorado Plateau.  

Campus Display Photos

		Basin & Range display looking NW

of Mohave County

ROCKS - Each digit on picture represents a rock.

1. Pegmatite
2. Obsidian
3. Volcanic Breccia
4. Hualapai Granite
5. Peach Springs Tuff
6. Proterozoic gneiss with veins
7. Proterozoic Granite
   from the Transition Zone
8. Diabase dike
9. Muddy Creek Conglomerate
10. Quartz
11. Biotite-Feldspar Pegmatite
12. Kaolin
13. Hualapai Limestone
14. Banded Rhyolite
15. Big Sandy Formation - Lizardstone
16. Meta Quartz Monzonite Porphyry
17. Welded Tuff Breccia