West Ord Mountains Mylonite (California)


506840 mE 3831476 mN 1245 m (UTM11N NAD83) (Google Maps)

Land Status:

Bureau of Land Management


This is an awesome ductile shear zone in Proterozoic orthogneiss of the Mojave block. The augens are quite spectacular, although shear-sense indicators are ambiguous. Such textures form in the mid to lower crust, where rocks deform in a ductile manner instead of in a brittle manner. This generally happens below about 15 km depth.

The rock is extremely hard, so bring a hefty sledge!


We stumbled upon this one. As far as I know, it hasn't been mapped or documented.

Site visited on 2/2/2013Page created on 11/15/2014