Kilometer-scale kinking of crystalline rocks in a transpressive convergent setting, central sierra nevada, california

摘要

Structural analyses in the Lake Edison area of the central Sierra Nevada, California, show that prominent north-nottheast-trending lineaments represent traces of joints and faults that have accommodated slip within a 4.8-km-wide right-lateral north-northwest-trending monoclinal kink band. The kilometer-scale kink band formed in Cretaceous granitic rocks, and the closely spaced, mineralized joints and faults formed at 79 Ma. Joints and faults strike approx 970 deg within the kink band and 020deg-030 deg outside the kink band. A kink-band kinematic model indicates that approx 3.7 (+ 2.1, -1.9) km of right-lateral displacement was accommodated across the kink band and that as much as 148 m of leftlateral slip on faults within the kink band occurred. A sensitivity study on four model parameters varied the angle made by the inner and outer limbs of the kink band, the number of faults within the kink band, and the kink-band width and length. This analysis yields estimates for right-lateral displacement across the kink band and left-lateral slip on faults within the kink band that fall into the range constrained by geologic relationships. Kinking may have been the last stage of right-lateral deformation, which started with development of the Rosy Finch shear zone. The presence of curved lineaments in the southern Sierra Nevada indicates that kilometer-scale kink bands may exist elsewhere in the Sierra Nevada batholith. Such arc-parallel kinking has been described in several other transpressive settings, and kilometer-scale kink bands may be a process by which late-stage, arc-parallel deformations is accommodated in convergent margins.