Geology of the Mt. Hyde - Fortification Peak area.


Gunn, Peter Robin.


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The area is situated approximately 10 kilometres north of Outram, (Fig. 1 :1) a small town on the Taieri Plains of east Otago. It has a basement of schist with isolated patches of Cretaceous quartz-rich sands and conglomerates, which are in part overlain by an olivine basanite extrusion.
The lithology, structure and mineralogy of the schist was studied. It was concluded that the schist belonged to the biotite-garnet zone of the greenschist facies. Structurally, four phases of deformation were recognised. Recent faulting is expressed in two regimes, NE/SW and the later NW/SE faulting.
Cretaceous quartz-rich terrestrial sediments were deposited in a time of marine transgression upon a peneplained surface. The quartz-rich sediments were subdivided into four units depending on the inferred paleo-environment.
The volcanic sequence is a peripheral outlier of the central Dunedin Volcano. It includes an assemblage of lherzolite xenoliths, clinopyroxene xenoliths, megacrysts and accidental xenoliths which are all described in detail. It is concluded that lherzolite and clinopyroxene xenoliths are genetically related and that megacryst phases have formed directly from the melt. Accidental xenoliths provide some rare and interesting mineral assemblages in their contact aureoles.

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84 leaves : illus. (part col.) map (in pocket) ; 30 cm.


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POLYGON ((170.073478889939111 -45.677264202929592,170.214733638598091 -45.680500446403315,170.311044012089326 -45.779856623564669,170.309239939476612 -45.817322757988649,170.148571711092217 -45.812232469351464,170.07150703259137 -45.715020671130993,170.073478889939111 -45.677264202929592))




Gunn, Peter Robin., “Geology of the Mt. Hyde - Fortification Peak area.,” Otago Geology Theses, accessed May 22, 2024,

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