Cenozoic evolution of the abrupt Colorado Plateau-Basin and Range boundary, northwest Arizona: A tale of three basins, immense lacustrine-evaporite deposits, and the nascent Colorado River

摘要: ABSTRACTIn northwest Arizona, the relatively unextended Colorado Plateau gives way abruptly to highly extended River extensional corridor within Basin and Range province along a system of major west-dipping normal faults, including Grand Wash fault zone South Virgin–White Hills detachment fault. Large growth-fault basins developed in hanging walls these faults. Lowering base level facilitated development Can-yon. This trip explores stratigraphic constraints on timing deformation paleogeographic evolution region. Highlights include relations that constrain structural demarcation between Range, zones, synextensional megabreccia deposits, non-marine carbonate halite deposits immediately predate arrival Colo-rado River, basalt fl ow interbedded with sediments.Structural indicate current physiography Plateau–Basin boundary Arizona began developing ca. 16 Ma, was essentially established by 13 has changed little since 8 Ma. The antiquity abruptness this boundary, as well record, suggest signifi cant headward erosion into high-standing plateau middle Miocene time. Thick late evaporite lacustrine long period internal drainage followed onset extension. widespread distribution such may signify, however, large infl ux surface waters and/or groundwater from possibly precursor River. Stratigraphic bracket through-fl owing 5.6 4.4 Ma.Keywords: