A gravity survey of the Wharekauhau Thrust, Palliser Bay, New Zealand

Abstract

A gravity survey undertaken at Wharekauhau, Palliser Bay, New Zealand, determines the geometry of the Wharekauhau Thrust. Gravity observations made along two profile lines perpendicular to the strike of the fault, enable two-dimensional models of the thrust and Miocene-Quaternary basin sediments to be constructed. Observed gravity is best modelled by a thrust dipping 25 ± 10° to the northwest over the depth interval 0–1 km. A second fault of steeper but unresolvable dip is modelled in the region of the Wharepapa River, across which Miocene-Quaternary sediments are downthrown c. 100 m to the east. The basin sediments produce a 25 mgal residual gravity low relative to the surrounding greywacke basement rock, which suggests a thickness of 1800 ± 500 m, similar to previously published estimates. © 2000 Taylor & Francis Group, LLC.