Metamorphic rocks in the Picuris Mountains

Outcrops of metamorphosed sedimentary rocks are exposed in the Picuris Mountains, north of NM Highway 75 and west of Dixon. Protoliths originate from the Yavapai accreted terrane from approximately 1.7 billion years ago. Figure 1 shows the field location, facing north, from Cerro de las Marquenas; a canyon cuts perpendicular to the west-plunging anticline. Figures 2-3 are outcrops of a quartzite member of the Rinconada Formation; a micaceous quartzite with remnant ripple laminae and bedding. Figure 4 is an outcrop of a schist member of the Rinconada Formation; coarse-grained, idioblastic staurolite twins, biotite and andalusite porphyroblasts indicate relatively high-temperature and low-pressure regional metamorphism. Imagine walking along a typical beach in southeast Asia before plants ever existed!