Quaternary faulting in Queen Valley,California-Nevada:Implications for kinematics of fault-slip transfer in the eastern California shear zone-Walker Lane belt

摘要

New geologic map,tectonic,geomorpho-logic,and terrestrial cosmogenic nuclide(TCN)geoctaronologic data document the geometry,style,kinematics,and slip rates on late Quaternary faults within the Queen Valley,California-Nevada area.These data provide important insight into the kinematics of fault-slip transfer from the dextral White Mountains fault zone northward into the Mina deflection.Queen Valley is an ~16-km-long,NE-trending basin bounded to the south by the White Mountains and underlain by four major Pleistocene to Holocene alluvial-fan surfaces.Four different fault types and orientations cut and offset all but the youngest surfaces:(1)The normal-slip Queen Valley fault,which consists of a set of NE-striking,NW-and SE-dipping normal fault scarps that cut across the SE side of the valley and offset all but the youngest surfaces;(2)discontinuous NE-striking,sinistral faults exposed on the north side of the valley;(3)the NW-striking dextral Coyote Springs fault,which merges into(4)a set of E-W-striking thrust faults.Measured offsets across normal fault scarps developed within ~(10)Be TCN-dated surfaces yield minimum late Pleistocene horizontal extension rates of 0.1-0.3 mm/yr.Documented fault geometries and slip orientations across Queen Valley suggest that fault-slip transfer models,such as the extensional displacement transfer,block rotation,and simple shear models,within the dextral fault system proposed for the eastern California shear zone-Walker Lane belt are not applicable to this part of the Mina deflection.Rather,dextral fault slip is transferred by both a restraining westward step and a releasing eastward step.Restraining and releasing bends have been extensively documented at a range of scales in strike-slip fault tectonic settings globally,and they have been simulated in analog models;thus,it is not surprising to document both within the ~630-km-long dextral shear zone that makes up the northern eastern California shear zone-Walker Lane belt Our results,combined with published slip rates for the dextral White Mountain fault zone and the eastern sinistral Coaldale fault,suggest that transfer of dextral slip into the Mina deflection is partitioned into three different components:horizontal extension along the Queen Valley fault,thrust faulting that merges into the dominantly dextral slip along the Coyote Springs fault,and dominantly sinistral slip along the Coaldale fault A velocity vector diagram of fault-slip partitioning across Queen Valley predicts a small component of contraction across the Coyote Springs and western Coaldale faults.Contraction across the Mina deflection is consistent with global positioning system data.An observed reduction in late Pleistocene fault-slip rates at the northern end of the eastern California shear zone and across the southwestern part of the Mina deflection may be explained by distribution of slip across a much broader zone than generally thought.