Gneiss boulder
This boulder of highly contorted banded gneiss was derived from the ancient crustal rocks exposed in the Little San Bernardino Mountains. This rock is Proterozoic in age, probably between 1.8 and 1.65 billion years (Barth and others, 2008). The boulder was transported downstream by mass wasting, flash floods, or debris flows before being deposited on the alluvial fans on the west flank of the Little San Bernardino Mountains. Erosion has re-exposed the boulder in the wash draining the uplifting Indio Hills.
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Last modified: 12/20/2010