Jasper Point Formation includes rocks exposed in the core of the Cotton Creek anticline in the southern part of the western Sierra Nevada metamorphic belt. Previously included in the revised Penon Blanco Formation, and cherts, here assigned to the Jasper Point Formation were informally called Hunter Valley chert by Taliaferro (1943). Consists of a stratified sequence of more than 900 m of massive, pillowed, and brecciated basalt overlain by 100 m of red, white, brown, and black, rhythmically layered radiolarian chert, both altered to prehnite or chlorite grade. Is interbedded with and gradationally underlies the Penon Blanco Formation. Age is Early Jurassic or older based on a radiometric age (U-Pb; zircon) from the Don Pedro pluton, which intrudes the Jasper Point Formation. (B1565)

Source: GNU records (USGS DDS-6; Menlo GNULEX).