Arizona Geological Society: Big Sandy Valley Field Trip Mohave County, Arizona

Arizona Geological Society members are invited to join the field trip as we visit Big Sandy Valley in Mohave County, Arizona.

This field trip, encompassing basin deposits, river integration, structural geology/tectonics, economic geology, and regional geology, will examine two generations of well-exposed basin deposits and associated faults and deformation in Big Sandy Valley, northwestern Arizona. Big Sandy Valley is situated along the margin between the Basin and Range Province and Transition Zone in Arizona within a ~90 km gap along the northwestern segment of the Laramide arc where no porphyry copper deposits have yet been defined. Two sedimentary lithium deposits were discovered in 2019 and continue to be advanced, while two subsurface porphyry copper prospects are being explored by junior mining companies. By examining the spatial distribution and geometric configuration of Big Sandy basin deposits, trip participants will evaluate and make connections between basin structural evolution, depositional systems and basin sedimentation, and modern resource exploration, highlighting the role geologic mapping plays in the intersection of science, policy, and land use. Field trip stops examine four aspects of basin evolution and mineral resources: 1) evaluate the character, form, and depositional environments of two generations of basin deposits (the Miocene Tule Wash beds and late Miocene-early Pliocene Big Sandy Formation) through type exposures; 2) examine the character, provenance, and depositional mechanisms of spectacular rock-avalanche breccia deposits in the Tule Wash beds; 3) evaluate the structural setting of basin deposits, cross-cutting relationships between faults and folds, and implications for the style and timing of deformation; and 4) summarize regional geology and implications for porphyry copper and sedimentary lithium mineralization.

Field Trip Leaders:  Brian F. Gootee, Lisa A. Thompson, Bradford J. Johnson, and Carson A. Richardson (Arizona Geological Survey, University of Arizona)