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| 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. The named basement rocks in the region include the Orocopia Schist and Chuckwalla Complex (Sylvester and Smith, 1987). Sedimentary clasts from these to lithologies are incorporated into the overlying conglomeratic beds of the Mecca Formation and younger formations in the region. |
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