EVALUATION OF MODERATE-FREQUENCY GROUND-PENETRATING RADAR FOR LOESS-COVERED BASALTIC LAVA FLOW FEATURES

Plains style volcanism is thought to be common on Mars, and terrestrial counterparts are often used to constrain eruption parameters such as flow rates and composition. However, most martian flows appear to have a dust cover of probable eolian origin that obscures fine-scale flow features, surface textures, and compositions from orbital spectral instruments, hindering comparisons. Quantifying relative amounts of martian dust cover would allow for better assessment of flow-surface textures and aid in estimating relative ages, eruptive processes, and compositions. The basaltic lava flows of the Eastern Snake River Plain (ESRP) offer an effective terrestrial analog for martian dust-covered flows as in some locations they are similarly covered with eolian sediments (loess). Previous studies have reported on the effectiveness of ground-penetrating radar (GPR) to survey either shallow buried targets or basaltic targets. For example, moderate-frequency soundings were used to detect buried permafrost and low-frequency soundings surveyed pristine uncovered volcanic features such as lava tubes, scoria layering, and volcanic rifts. However, there is limited data yet available on the application of GPR to survey shallow buried basaltic targets. This study evaluates the use of moderate-frequency (250 MHz antenna, 125-375 MHz bandwidth) GPR soundings to detect shallow flow-surface textures and volcanic rift structures for the loess-covered basaltic lavas of the ESRP. We examine radar profiles from four locations: surface flows near an eruptive center, a phreatomagmatic cone, a kipuka, and a volcanic rift zone. In spite of the potential difficulties presented by the conductivity of the loess cover, we find that in the arid conditions of the ESRP our radar soundings resolve not only the loess-lava interface, but small-scale (10cm to one meter width, half to a meter depth) surface features of the buried flows as well as larger structural variations (tension cracks and sags at several meters depth) associated with the volcanic rifts. This type of data is key in constraining eruptive styles, burial depths, and thus relative ages and flow types of remotely sensed terrestrial and martian basaltic lava fields.