A bedrock gourge cut out by the Swift river in Byron, Maine. USA
At Coos Canyon, the Swift River cuts through the Perry Mountain Formation of Silurian age (418-443 million years). Named for exposures on Perry Mountain near Rangeley, this unit consists of alternating layers of quartzite and schist, typically in beds a few inches thick. The quartzite layers were originally fairly clean quartz sand, although some beds probably contained some clay minerals as well. The schist was originally silt and mud. Heat and pressure caused by multiple episodes of mountain building transformed these original sedimentary materials to the metamorphic rocks exposed today.
LEARN MORE about Coos Canyon and panning for gold.