Gopher Ridge Volcanics
Gopher Ridge Volcanics
early Late and late Middle Jurassic, Callovian to Oxfordian
Volcanic breccia, tuff, and flow rock, ranging from basalt to rhyolite but mostly andesite. Some massive felsic rock probably formed as shallow, late-stage intrusives. Some flow rock exhibits pillowed structure. In most areas the tuffaceous rocks have a slatey parting whereas the breccia and flow rock are unfoliated; locally schistose. Metamorphic minerals include epidote, albite, tremolite, and some chlorite, indicative of greenschist facies metamorphism.