The Lompico Sandstone is a sedimentary rock formation of lower to middle Miocene age. It overlies the Salinian basement rocks of Santa Cruz County, California. It interfingers with and is overlain by the Miocene Monterey Formation. These are in turn overlain by the mid to upper Miocene Santa Margarita Sandstone which is in turn overlain by the upper Miocene Santa Cruz Mudstone.[1]