Taringatura group in the Overton's Road section, Upper Otamita stream, Southland
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Abstract:
A measured section through the Taringatura Group in the upper Otamita Valley is presented. The units recognised in the section have formed the basis of mapping in the areas north-west and south-east of the section.
The area is affected by the North Peak Flexure, and mapping confirms that the internal radius of this fold has been shortened by the northward displacement of wedge shaped blocks, with dimensions in the order of kilometres.
The Taringatura Group represents a mainly regressive sequence, with the lower part of the section dominated by deep-water turbidites, interbedded with ash, debris-flow and bottom-current deposits. Higher in the sequence shallow water deposits predominate, including some with storm-generated sedimentary structure. The depositional model proposed is that of the progradation of shelf and slope facies over a gently plunging trough axis. Two disconformities interrupt the sequence and each may represent uplift and subaerial erosion.
New Zealand mid-upper Triassic series and stages are recognised. Parts of the section may be subdivided on lithological grounds and, in addition to recognizing existing rock units, three new lithologic zones are proposed: the Mervyn Peake Flysch Zone, the Overton Silstone(Zone) and the Caroline Tuff Zone. Of these only the latter is of regional extent.
Clast composition varies from andesitic, with minor granitoid, at the base of the Taringatura Group, to rhyolitic-dacitic with abundant granite, and finally at the top of the group, a return to andesitic. Detrital quartz and alkali feldspars, rare throughout most of the section become abundant in upper Warepan and Otapirian strata.
Petrography and the abundance of air-fall ashes suggests that the site of deposition was a basin associated with and receiving detritus from an area of active arc volcanism.
The area is affected by the North Peak Flexure, and mapping confirms that the internal radius of this fold has been shortened by the northward displacement of wedge shaped blocks, with dimensions in the order of kilometres.
The Taringatura Group represents a mainly regressive sequence, with the lower part of the section dominated by deep-water turbidites, interbedded with ash, debris-flow and bottom-current deposits. Higher in the sequence shallow water deposits predominate, including some with storm-generated sedimentary structure. The depositional model proposed is that of the progradation of shelf and slope facies over a gently plunging trough axis. Two disconformities interrupt the sequence and each may represent uplift and subaerial erosion.
New Zealand mid-upper Triassic series and stages are recognised. Parts of the section may be subdivided on lithological grounds and, in addition to recognizing existing rock units, three new lithologic zones are proposed: the Mervyn Peake Flysch Zone, the Overton Silstone(Zone) and the Caroline Tuff Zone. Of these only the latter is of regional extent.
Clast composition varies from andesitic, with minor granitoid, at the base of the Taringatura Group, to rhyolitic-dacitic with abundant granite, and finally at the top of the group, a return to andesitic. Detrital quartz and alkali feldspars, rare throughout most of the section become abundant in upper Warepan and Otapirian strata.
Petrography and the abundance of air-fall ashes suggests that the site of deposition was a basin associated with and receiving detritus from an area of active arc volcanism.
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162 leaves : ill., maps ; 30 cm.
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1982Kirk
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Location (WKT, WGS84):
POLYGON ((168.670765733120959 -45.985012971000984,168.665948752760329 -46.029127473233316,168.609722735229553 -46.026739208491129,168.613902816132281 -45.982602472553701,168.670765733120959 -45.985012971000984))
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Citation
Kirk, Philip Alastair., “Taringatura group in the Overton's Road section, Upper Otamita stream, Southland,” Otago Geology Theses, accessed April 22, 2025, https://theses.otagogeology.org.nz/items/show/157.