Geophysics of the Te Anau and Waiau depressions, western Southland

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Anderson, H.J. 1980 Geophysics of the Te Anau and Waiau depressions, western Southland. [s.l.]: [s.n.]. Report / Geophysics Division 180 52 p.

Abstract: All available geophysical data for the Te Anau and Waiau depressions have been collated and interpreted. The central Te Anau depression is marked by a gravity minimum which represents a thickness of about 900m of Pliocene-Quaternary sediments. Pre-Pliocene rocks have relatively high densities which in some areas have ranges overlapping those of the basement rocks. In places, however, accumulations of less dense pre-Pliocene sediments produce an appreciable negative anomaly (70 micron/kg in the Haydocks area). Interpretation of magnetic anomalies suggests that basement is close to the surface near Centre Island in Lake Te Anau and the fault or fault zone defining the eastern edge of Fiordland probably occurs to the east of the island. Combined seismic, gravity and magnetic interpretations indicate that the Waiau depression contains a maximum sediment thickness of about 3000m near the Lillburn Valley. Basement rocks are interpreted to occur within 800m of the surface in Te Waewae Bay. Magnetic data indicate that rocks related to the Longwood complex probably underlie the depression as far west as Sand Hill Point. The Waiau depression is separated from the Solander basin by the Hump Ridge-Midbay High