Inch Clutha gravity and magnetic survey

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Whiteford, C.M.; Reilly, W.I. 1971 Inch Clutha gravity and magnetic survey. [s.l.]: [s.n.]. Report / Geophysics Division 58 11 p.

Abstract: A detailed gravity and magnetic survey in the Inch Clutha area, South Otago, has defined more precisely an anomaly which appears to arise from an intrusion of igneous rock of density contrast > 0.3 Mg/cubic m with respect to the surrounding greywackes. This anomaly is an extension of the positive gravity (and magnetic) anomaly zone which coincides with the lower Permian Tuapeka Group in eastern Southland and Otago, but at Inch Clutha is displaced southwards over the stratigraphically higher middle Permian Waipahi Group. The upper surface of the source body appears to dip northwards at about 20 degrees, and its cross-section is of the order of 25 sq. km. It probably approaches within a few hundred metres of the surface near the outcrop of the Otanomomo igneous complex, which may represent a sill associated with the main intrusion. An analysis of the direction of magnetisation of the source body suggests that the vector has been rotated southwards from the present direction of the field, in the tilting of the Permian strata. (auth)