Taratu formation in North east Otago.

Author:

Aitchison, J. C. (Jonathan Clement)

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Abstract:

The Taratu Formation sediments, as seen in north east Otago are described. The name Taratu is previously unused in this area but should apply to all the lithologically and stratigraphically equivalent non-marine quartzose conglomerates of (at last) the Otago area.
Thirteen depositional facies are recognised with their interpretation being that of either fluvial or littoral origin. Textural study allows the description of five textural facies based on grain-size analysis. One textural facies dominates that of sandy gravel, and typical exposures contain a predominance of coarse over fine-grained sediments.
Scanning Electron Microscopy allows the recognition of two end member quartz types (milky and clear quartz) with a gradation between. Authigenic precipitation of kaolinite and quartz is also seen. A macroflora from Livingstone is described and the discovery of the only fossil insect (an impression of a beetle larvae) at present known in the New Zealand fossil record is reported.
The Taratu Formation is of possibly significant economic importance being a large scale low grade placer gold deposit. Coal is also found in localised lenses.
Facies model interpretation of the Taratu Formation, in the light of existing outcrop, is that of a pediplainlike deposit which formed with deposition in braided rivers which flowed on top of a peneplain surface of deeply chemically weathered Haast Schist. Analogy with contemporary savanna areas is made.
The age of the Taratu Formation in north east Otago ranges from late Cretaceous to Eocene.

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Thesis description:

178 p. : ill., maps (one fold.) ; 30 cm.

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OU geology Identifier:

1981Aitchison

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Location (WKT, WGS84):

POLYGON ((170.428746754662313 -44.842294723752573,171.119558137669628 -44.853204961981376,171.109598765110547 -45.156715010878827,170.865931306430184 -45.146465864218058,170.869255284259197 -45.057213242496026,170.424035849035192 -44.891610974549195,170.428746754662313 -44.842294723752573))

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http://download.otagogeology.org.nz/temp/Abstracts/1981Aitchison.pdf

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Citation

Aitchison, J. C. (Jonathan Clement), “Taratu formation in North east Otago.,” Otago Geology Theses, accessed May 22, 2024, https://theses.otagogeology.org.nz/items/show/140.

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