Wednesday, June 24, 2009
Our second side hike of the day was up Blacktail Canyon. Blacktail is cut into Tapeats Sandstone, but bottoms out in the Schist, so the unconformity is well-displayed at eye level.
The unconformity consists of horizontal sandstone layers (a mere half a billion years old) sitting directly on top of 1.5 billion year old metamorphic rocks. The sandstone is basically the preserved fossil beaches that washed across the eroded schist during an ancient period of rising sea level. The lowest layers of the Tapeats contain big chunks of the underlying rocks, including large pieces of vein quartz. I tried to picture myself sitting on that rocky shoreline, watching the waves roll the gravel around.
Maybe there is something about a missing billion years of geologic history that adds something mysterious or spiritual to this place. We all gathered in the quiet canyon bottom while Greg told a eery story about nightime in the canyon - it wasn't hard to imagine the drumming. And I'm sort of glad we didn't camp here.