Geophysics of the Moutere Depression

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Anderson, H. 1980 Geophysics of the Moutere Depression. : . Report / Geophysics Division 159 41 p

Abstract: The Moutere Depression is characterised by a linear belt of positive gravity and magnetic anomalies which obscures most other anomalies. However, three gravity minima have been recognised, and those at Richmond and in Tasman Bay are most clearly related to a thick sedimentary sequence. Depths of at least 1650 m and 1900 m, respectively, are indicated. The Waimea Fault, which forms the the eastern boundary of the Moutere Depression, is a high angle reverse fault. Dips of the fault previously calculated from gravity measurements appear to be too low because the gravity effect of Brook Street Volcanics, which probably underlie the Cenozoic sequence west of the fault, has not been considered. Combined interpretation of gravity and magnetic maxima suggest that these anomalies are caused by a dense magnetic body or series of bodies within the basement. In some places, for example Ruby Bay, a basement ridge may contribute to these positive anomalies. Interpretation of several short seismic lines has suggested that the thickness of sediment near Brightwater and Golden Downs is about 1500 m. (auth)