Tertiary geology of the Wairaki station area, Mid-Waiau valley, Southland, New Zealand.
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Abstract:
The upper Eocene to lower Oligocene sediments along the eastern margin of the mid-Waiau Valley, Southland, record a change from fluvial-lacustrine and marginal marine (Nightcaps Group) conditions to deeper marine calcareous muds (Waicoe Mudstone).
The Runungan age Beaumont Formation was derived from the Fiordland Complex to the west and deposited in distal to proximal sandy braided stream environments and locally in flood plain and lacustrine environments. The sudden late Eocene transition from terrestrial Beaumont Formation to marginal marine Orauea Mudstone resulted from a combination of basin subsidence and a eustatic rise in sea-level.
Whaingaroan age sediments are missing in the study area due to 1500 + meters of normal movement on the westward dipping Waicoe Fault. Displacement on the Waicoe Fault probably occurred during the Whaingaroan (lower Oligocene) stage and is inferred to represent a major basin margin fault.
Deep-water restricted benthonic Foraminifera in the upper Oligocene-lower Miocene Waicoe Mudstone indicate that basin subsidence had largely occurred by this time. The introduction of redeposited shelf debris during the Otaian and early Altonian suggest renewed basin margin tectonism.
The occurrence of a lower Miocene diatomaceous ooze suggests local upwelling of nutrient rich water along the eastern basin margin.
The Runungan age Beaumont Formation was derived from the Fiordland Complex to the west and deposited in distal to proximal sandy braided stream environments and locally in flood plain and lacustrine environments. The sudden late Eocene transition from terrestrial Beaumont Formation to marginal marine Orauea Mudstone resulted from a combination of basin subsidence and a eustatic rise in sea-level.
Whaingaroan age sediments are missing in the study area due to 1500 + meters of normal movement on the westward dipping Waicoe Fault. Displacement on the Waicoe Fault probably occurred during the Whaingaroan (lower Oligocene) stage and is inferred to represent a major basin margin fault.
Deep-water restricted benthonic Foraminifera in the upper Oligocene-lower Miocene Waicoe Mudstone indicate that basin subsidence had largely occurred by this time. The introduction of redeposited shelf debris during the Otaian and early Altonian suggest renewed basin margin tectonism.
The occurrence of a lower Miocene diatomaceous ooze suggests local upwelling of nutrient rich water along the eastern basin margin.
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100 leaves : ill. (some col.), maps ; 30 cm.
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1983Griffith
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POLYGON ((167.659741277376696 -45.789419166762961,167.78465853065677 -45.796991925653607,167.776436710499667 -45.944519274527046,167.646059374155953 -45.937039298934728,167.659741277376696 -45.789419166762961))
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Citation
Griffith, Roger Clinton., “Tertiary geology of the Wairaki station area, Mid-Waiau valley, Southland, New Zealand.,” Otago Geology Theses, accessed April 23, 2025, https://theses.otagogeology.org.nz/items/show/164.