Greywacke Structure and Petrography around Benmore Dam, North Otago.


Shu, YK


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The area investigated lies within Benmore and Hewlings Survey Districts of Otago and Canterbury respectively; covering approximately the southern end of the Waitaki Gorge. The area consists of a one and a half mile strip on either side of the Waitaki River with Black Jacks Point as the northern boundary and the main road through Otematata as the southern boundary.
Basement rocks or metagreywackes of this area are part of the Torlesse Group of the Alpine Facies. It is known to be structurally very complex and lies within the prehnite and pumpellyite metagreywacke facies. The construction of Benmore Dam has resulted in numerous road-cuts and excellent exposures around the dam site. In view of these advantages and the eventual loss of many outcrops beneath the future Lake Benmore, this project was initiated in an endeavour to elucidate the possible structure and to establish a general picture of the tectonic history.
The term "argillite" in the following pages is used to denote fine grained rocks including siltstone, mudstone and ash bed; while lithic, tuffaceous and micaceous sandstone and arkose are covered by the term "greywacke". Aerial photographic coverage of the area is given by run 2726, photographs 14 17 and run 2725, photographs 16 - 18.

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62 leaves, photos, Map (folded in pocket); 27 cm.


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POLYGON ((170.117446650668654 -44.600447943823497,170.117486953121954 -44.586157628599473,170.160538244425169 -44.578185751134484,170.170100603576685 -44.532214366775875,170.197188330471164 -44.522878812321416,170.289583906610602 -44.569414025336194,170.250309026209777 -44.610872237134764,170.260586681834724 -44.619217815328668,170.242736258554032 -44.64403587132621,170.117446650668654 -44.600447943823497))




Shu, YK, “Greywacke Structure and Petrography around Benmore Dam, North Otago.,” Otago Geology Theses, accessed May 22, 2024,

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