Evolution of a Miocene-Pliocene low-angle normal-fault system in the southern Bannock Range, southeast Idaho.

摘要

Structural and basin analyses in the Clifton quadrangle of southeast Idaho indicates that the modern Basin-and-Range topography is 4 Ma and that the bulk of Cenozoic extension was accommodated by slip on the older Bannock detachment system. The detachment system was active between ∼12 and 4 Ma and accommodated ∼50% extension.; Cross-cutting relationships show that the master detachment fault was active at a low angle and has not been rotated to a low-dip angle through time. Map patterns show that the hanging wall to the detachment system began as a cohesive block that later broke up along high-angle normal faults. The Miocene-Pliocene Salt Lake Formation was deposited in the hanging wall during extension on the system.; The Bannock detachment system strongly resembles detachments documented in metamorphic core complexes. Therefore, we interpret the Bannock detachment system as a proto-metamorphic core complex, akin to the Sevier Desert detachment fault.