Serpentinite here marks another ophiolite, but it is quite mysterious in the scheme of the Sierra Nevada. For one thing the ages of the rocksthe times of their crystallization or metamorphismrange widely from 280 to 380 Ma. For another, it appears to have been metamorphosed more strongly than its neighboring rock units, unlike the majority of cases. Whatever this set of rocks is, some very pretty serpentinite is revealed in this roadcut. This stretch of the East Branch North Fork Feather River is called Serpentine Canyon, and not just because the Union Pacific Railroad takes a lot of curves climbing up the grade.