Outcrop‐scale imaging of lacustrine delta sediments using ground penetrating radar and seismic methods

Abstract

We imaged the complex stratigraphy and structure of poorly unsaturated consolidated fluvial and lacustrine sediments that are well exposed in a road cut along the margins of the Western Snake River Plain in southwest Idaho. The outcrop contains a 10‐m exposure of a delta sequence with topset beds tectonically tilted 10°, underlain by 25° dipping foreset sand beds with shale drapes, and cut by near‐vertical faults. Beneath the foresets are clay sediments over an irregular rhyolite bedrock surface. We collected 100 MHz frequency ground penetrating radar (GPR) and high‐resolution reflection seismic profiles along this roadcut to image the geologic structure below the road surface. The GPR data show the observed dip of both the foreset and topset beds to the depth of about 6 m. The seismic data show unclear reflection results, however it can be estimated the reflection from the bed rock surface at about 30 m. The imaging studies will be extended to 3‐D GPR coverage, higher frequency seismic data collection, and more sophisticated processing routines to improve the quality and utility of GPR and seismic surveys to image sub‐meter scale geologic stratigraphy and structures.