Brothers Fault Zone

D. Dziekan

Overview

• Regionally extensive fault zone

• Faulting strikes mainly northwest

• Alec Butte overlooks faulting

Alec Butte

• Cinder cone

• Overlies olivine basalt dated at 6.68ma

• Formed before faulting– Cut by faults

• 2.89 ma Iron Mt. unbroken

• Dating planned of Alec Butte– determine if faults happened post 2.89ma

Dashed northwest, solid northeast

Brother’s Fault

• Dextral oblique-normal fault

• Strike-slip to dip-slip ratio 1:1

• Some faults crosscut normal strike

• Model designed to explain crosscut faults