The utility of conductivity surveying and resistivity sounding in evaluating sand and gravel deposits and mapping drift sequences in northeast Scotland

Abstract

Two types of ground geophysical survey, using portable equipment capable of one-man operation, have been used with the aim of elucidating the thickness and extent of sources of potentially workable sand and gravel in northeast Scotland. Vertical resistivity soundings have provided point data that allow extrapolation of the drift succession between exposures, boreholes and trial pits. Lateral profiling of ground conductivity using a non-contacting electromagnetic conductivity meter has proved to be of little use as an aid to conventional geological mapping in determining the position and extent of surface spreads of sand and gravel. Resistivity sounding, using Offset Wenner apparatus in particular, represents a rapid, low-cost method applicable by industry to the preliminary investigation of the thickness of sand and gravel at proposed extraction sites, especially in areas where modern geological maps are not available, or where ground disturbance has to be minimised.