Electrical resistivity soundings on the Moawhango Tunnel line

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Dawson, G.B. 1976 Electrical resistivity soundings on the Moawhango Tunnel line. [s.l.]: [s.n.]. Report / Geophysics Division 110 10 p.

Abstract: Five electrical resistivity soundings were made along the Moawhango tunnel line, in April 1974. An ash overburden 3 to 10 m thick is underlain by weathered greywackes of resistivity less than 260 ohm metres which act as a near surface aquifer. Weathering decreases with depth until, at a depth of 20 to 28 m along the ridge to the north and at 90 m in the Paradise valley, a high resistivity zone of 1700 to 2500 ohm metres, most likely unweathered greywacke, is reached. Underlying the high resistivity zone at depths ranging from 115 to 165 m is a zone of lower resistivity (750 to 1000 ohm metres) which is interpreted as due to greywacke of higher permeability or to argillite. At greater depths some 260 to 500 m below the ground surface is a zone of higher resistivity, 1500 to 1650 ohm metres, almost certainly representing saturated, very low porosity, unweathered greywacke