PT - JOURNAL ARTICLE AU - Gawthorpe, R. L. AU - Collier, R. E. Li AU - Alexander, J. AU - Bridge, J. S. AU - Leeder, M. R. TI - Ground penetrating radar: application to sandbody geometry and heterogeneity studies AID - 10.1144/GSL.SP.1993.073.01.24 DP - 1993 Jan 01 TA - Geological Society, London, Special Publications PG - 421--432 VI - 73 IP - 1 4099 - http://sp.lyellcollection.org/content/73/1/421.short 4100 - http://sp.lyellcollection.org/content/73/1/421.full SO - Geological Society, London, Special Publications1993 Jan 01; 73 AB - Ground penetrating radar (GPR) offers a high-resolution, shallow subsurface profiling technique for use in sedimentological and reservoir analogue studies. GPR is similar to seismic reflection profiling but uses electromagnetic radiation in the 50 to 500 MHz frequency range (in geological applications). By using these relatively high frequencies, high resolution data can be obtained. Short duration pulses of electromagnetic energy are transmitted into the ground, reflected from interfaces across which there are abrupt changes in dielectric properties, and are detected by a receiver. These received signals are displayed in nanoseconds two-way time and may be recorded digitally allowing subsequent processing. Some 1000 m of 2D GPR profiles were collected from a modern point bar on the Madison River, Montana USA and have been interpreted using an approach similar to seismic stratigraphic analysis. This has allowed identification of a number of radar sequences and radar facies. Radar sequence boundaries are identified by reflector terminations (onlap, downlap, toplap and erosional truncation) and represent episodes of erosion during the development of the point bar. In contrast, radar sequences and their component radar facies record phases of accretion of the point bar. Each radar sequence is linked to a discrete accretionary unit that can be mapped on the surface of the point bar. Mapping of the radar sequences and radar facies has allowed quantification of their 3D geometry.