Hislop: Bedrock Geologic Map of part of the Joshua Tree South 7.5 Minute Quadrangle, Southern California

Bedrock geologic mapping at 1:24000 scale, including structural, petrologic, and kinematic analysis at the outcrop to thin section scale, will provide first order constraints on the extent, geometry and displacement of young “protofaults” in the Little San Bernardino mountains near Joshua Tree National Park (CA). The faults are hypothesized to be related to complex block rotations in a narrowly confined crustal wedge between two larger faults of the San Andreas system in the Eastern Transverse Ranges. Mapping by Ph.D. candidate Ann Hislop will take place during late fall 2016 and spring 2017 and will be supervised by the PI and scientists from the U.S.G.S. Existing geologic maps by U.S.G.S. collaborators are at too small of a scale to reveal the structural details needed to elucidate precise location, kinematics, and evolution of inferred faults. Also, existing maps don’t show the lithologic complexity of rocks in which the protofaults occur. The shallow expression of faulting will aid in interpretation of regional seismicity and tectonics, and in understanding of the evolution of fault zones. Detailed mapping in the central map area will be compared with Lidar data collected as part of a NCALM grant awarded to Hislop. Results will be shared with personnel from Joshua Tree National Park for their outreach and public information mandate.