DAVIS, J.L. and ANNAN, A.P. 1989. Ground-penetrating radar for high-resolution mapping of soil and rock stratigraphy. Geophysical Prospecting 37, 531-551.Ground-penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions. The need to better understanding overburden conditions for activities such as geochemical sampling, geotechnical investigations, and placer exploration, as well as the factors controlling groundwater flow, has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible.The areas of application for ground-penetrating radar are diverse. The method has been used successfully to map ice thickness, water depth in lakes, bedrock depth, soil stratigraphy, and water table depth. It is also used to delineate rock fabric, detect voids and identify karst features. The effective application of the radar for the high-resolution definition of soil stratigraphy and fractures in bedrock is highlighted.The basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories. One example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m. Two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine. Another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination. The corroboration of the radar results by borehole investigations demonstrates the power and utility of the high-resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes. With the advent of new instrumentation and field procedures, the routine application of the radar method is becoming economically viable and the method will see expanded use in the future.

A VHF impulse radar system operating on the ground is a viable technique for mapping the near‐surface geological structure and electrical properties of permafrost. A fixed antenna configuration transported over the surface yields a reconnaissance map of two‐way travel times for subsurface reflectors. Wide‐angle reflection and refraction (WARR) sounding determines propagation velocity versus depth when performed in layered areas. To obtain a WARR sounding, one measures travel time versus antenna separation. These techniques were field tested in the Tuktoyaktuk region of the Mackenzie River delta, N.W.T. Data recording was on a graphic display for initial field analysis and on analog magnetic tape for subsequent processing. Reconnaissance surveying has mapped structural features at various depths between 3 and 30 m. The electrical loss of the soils at a site limits the penetration depth. Clays and silts attenuate the radar signal more than sands and gravels. WARR soundings have determined dielectric constant versus depth in layered areas. While impulse radar is useful in delineating geological structure, core drilling is required to determine the geological composition.

The “Spanish Flu” killed over 40 million people worldwide in 1918. Archival records helped us identify seven men who died of influenza in 1918 and were interred in Longyearbyen. Svalbard, Norway, 1300 km from the North Pole. Ground Penetrating Radar (GPR) was used successfully, in a high-resolution field survey mode, to locate a large excavation with seven coffins, near the existing seven grave markers. The GPR indicated that the ground was disturbed to 2 m depth and was frozen below 1 m. Subsequent excavation showed that: a) the GPR located the position of the graves accurately, b) the coffins were buried less than 1 m deep, and c) that the frozen ground was 1.2 m deep where the coffins were located. The GPR assisted in planning the exhumation, safely and economically, under the high degree of containment required. Virologic and bacteriologic investigations on recovered tissues may give us an opportunity to isolate and identify the micro-organisms involved in the 1918 influenza and expand our knowledge on the pathogenesis of influenza.

Dry salt has a very low electrical conductivity which permits radio signals to be transmitted through substantial thicknesses of salt with little attenuation. Radar sounding experiments conducted in several potash mines in Saskatchewan, Canada, confirm that radar is an effective method for probing salt environments. The experiments had two main objectives: namely, to assess the utility of impulse radar for mapping stratigraphy in the salt beds above, below, and beside mining tunnels and to determine the electrical character of the potash beds in situ, since little information was available on the radio‐frequency properties of potash ore. The experiments were conducted with an impulse radar system using antennas which radiated pulses having center frequencies between 100 and 1000 MHz. The higher frequency antennas detected thin clay beds and stress‐relief cracks to depths of several meters. Sounding for deeper structure known to exist at ranges of several tens of meters was not always successful. The lower frequency antenna systems were found most useful for deeper sounding; in some instances known geologic horizons were detected at depths of up to 20 m. Deeper structure was frequently masked by shallow, high‐reflectivity stress‐relief cracks. The potash deposits were found to have a bulk dielectric constant in the range 5 to 6. In many areas, the evaporites have a significant clay content which governed the signal attenuation. Depth of penetration of the radar was generally greater in areas of lower clay content.

Field trials with a VHF impulse radar have been undertaken in the Tuktoyaktuk, N.W.T. area during the summer of 1973 and the spring seasons of 1974 and 1975. The radar transmits a wavelet with a centre frequency of 110 MHz and a pulse duration of 18 ns. Separate transmitter and receiver antennas were used.Preliminary interpretation of the data obtained at the Involuted Hill test site indicates that ice/sand interfaces were detected to ranges greater than 30 m. In icy sand, ice lenses separated by 3 m were resolved. Clay-till/ice interfaces were not detected at ranges greater than about 3 m. At other sites near the village of Tuktoyaktuk, sand/clay-till interfaces were detected at ranges greater than 5 m.Wide angle reflection and refraction sounding yields estimates of reflector depths and propagation velocities. Radar has proven useful in delineating geologic structure, but bore-hole control is required for identification of the geological composition of the structure.