Tertiary Extension and Fault-Block Rotation in the Transition Zone, Cedar Mountains Area, Arizona v. 1.1

Brand, P.K.; Stump, E.

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Citation

Brand, P.K., and Stump, E., 2005, Tertiary Extension and Fault-Block Rotation in the Transition Zone, Cedar Mountains Area, Arizona v. 1.1: Arizona Geological Survey Contributed Map CM-11-A, map scale 1:24,000, 121 p. and 3 map sheets.

Publisher

Arizona Geological Survey (Tucson, AZ)

Description

New geologic mapping from the Cedar Mountains - Bloody Basin - Cooks Mesa area in the central Arizona Transition Zone presents an enigmatic geologic relationship that has previously gone unstudied. Here, fault blocks of Early Proterozoic basement overlain by Tertiary sedimentary and tuffaceous-lacustrine deposits and capped by a thick accumulation of basalt flows, dated in the project area between 15.1 and 13.5 Ma, are rotated ~20o west to west-southwest along east-dipping normal faults. Half-grabens formed during rotation are filled with a syn- to post-extensional basin-fill conglomerate, and are locally overlain by flat-lying and post-extensional basalts, dated in this study at 6.4 Ma. The extended area is a graben, bounded to the west by the eastern flank of Cooks Mesa, a flat-lying expression of the same general stratigraphy, and to the east by the Mazatzal Mountains. Faults in the project area strike north and northwest and are interpreted to merge with the Cooks Mesa fault, a listric normal fault, at depth. The graben, named in this study the Lower Verde Valley graben, continues southward out of the project area parallel to the Verde River, and northward across the Bloody Basin. New dates from this research bracket the timing of the extension in the project area between 13.5 Ma and 6.4 Ma. The timing is coeval with the Basin and Range disturbance in Arizona, yet the style of extension in the project area is not consistent with the published understanding of this event. Here, rather than the expected high-angle normal faults and offset without rotation, extension was accommodated by motion along a listric normal fault and rotation of fault blocks. This unusual setting provides a new view into the dynamics of the Basin and Range disturbance in the Arizona Transition Zone. Report and three map sheets - geologic map (1:24,000 map scale), cross-section sheet with 5 cross-sections, legend.

URI

http://hdl.handle.net/10150/630633

Additional Links

https://library.azgs.arizona.edu/

Language

Series/Report no.

CM-11-A

Rights

Collection Information

Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu.

North Bounding Coordinate

34.125

South Bounding Coordinate

West Bounding Coordinate

-111.875

East Bounding Coordinate

-111.75

Collections

AZGS Document Repository