The Precambrian-age (Proterozoic) basement complex rocks exposed
in upper Painted Canyon consist of schist and gneiss with granitic intrusions,
such as these contorted and offset aplite dikes. Aplite, a rock consisting
dominantly of quartz and light-colored feldspar, forms as intrusions deep
in the crust in the range of 10 miles or more where heat and pressure are
great enough to allow low temperature minerals to melt and migrate into
surrounding rocks. Elsewhere in the region, the basement rocks named basement
rocks include the Orocopia Schist and Chuckwalla Gneiss. Sedimentary clasts
from these to lithologies are incorporated into the overlying conglomeratic
beds of the Mecca Formation and younger formations in the region. |