Imaging the subsurface stratigraphy in the Ubehebe hydrovolcanic field (Death Valley, California) using ground penetrating radar

Abstract

Ground penetrating radar (GPR) surveys were carried out to collect subsurface images of the basaltic base surge deposits in the Ubehebe hydrovolcanic field, Death Valley National Park, California. Antennae with frequencies of 50, 100 and 200 MHz were used. This technique allowed the collection of useful geologic data, for example, the lower stratigraphic boundary of the pyroclastic deposits can be imaged and their thickness can be estimated. Different radar responses were also obtained from base surge deposits and underlying sedimentary rocks, which enable their recognition where no outcrops are available. Furthermore, GPR data confirmed the presence of small, eroded craters, which are partially filled by alluvium. In this case, an unconformity between the overlying, horizontally bedded alluvium and the underlying bowl-shaped base surge deposits can be recognized within the crater and the thickness of the alluvium estimated. Common mid-point (CMP) surveys suggested subsurface velocities of the electromagnetic waves in the upper part of these deposits between 0.095–0.1 m/ns.