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Volume 80, 1952
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V. Foliated Mica-schists

Distribution. A belt of rock extending with decreasing width from Taramakau Valley north-east past Crooked River through Haupiri Valley to Ahaura Valley is mapped as foliated schist. The belt adjoins the non-foliated schists on the east and is cut off on the west by the Alpine Fault. The belt was not examined in detail and the mineralogical rank of its western edge is uncertain.

Content. This belt consists of mica-schists with coarse foliation and perfect schistosity. In its upper part bedding is occasionally visible, but in its lower part the greater metamorphism has mostly obliterated it. Within this belt to the south McKay mapped sills of metamorphosed ultra basic rocks. He called them “Magnesian Rocks” or “Mineral Belt.” On his map they are shown as an extremely narrow belt offset about five miles at Taramakau River. Bell and Fraser and Morgan mapped the ultrabasics from Whitcombe River to Taramakau River. They called them the “Pounamu Series.” On their maps they showed them not as a continuous belt but as isolated lenses elongated along the strike of the beds. On the south side of the Taramakau these lenses are confined to a milewide belt which roughly corresponds in position with the narrower belt mapped by McKay. Within the mapped area Wellman (1944, p. 234b) has reported ultrabasic sills on the north side of the Taramakau Valley (Orangapuku River and Soapstone Creek). As on the south side of the river these sills strike north-east parallel to the schist. The ultra-basic sills do not line up across the Taramakau River, those on the north side being offset five miles east with respect to those on the south side. The schists that enclose the ultra-basic sills are of the same rank on both sides of the river, and this offset is almost certainly due to horizontal displacement that has taken place on the Taramakau-Hope Fault.

Ultra-basics have not been found in place immediately north of Taramakau River, but fragments are not uncommon in streams up to and just beyond Crooked River. No ultra-basic outcrops or fragments were seen between Evans River and Ahaura River. To the north, fragments are common in Nancy and Tass rivers. The most northerly ultra-basic outcrop in the alpine schist is at Mill Creek, a tributary of Maruia River (Henderson and Fyfe, Geological map of

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Fig. 1—Locality Map showing location of Fig. 2 and relation between Monotis localities and Undermass Structure.

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Fig. 2—Geological Sketch Map of Sheet S.32 (Harper Pass).

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Fig. 3—Cross Sction A-A' and Map Reference.

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Fig. 4—Map of upper Trent River showing structure and topography.

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Fig. 5—Trent River from Main Divide. Mount Monotis at extieme left of photo. Fossil locality on ridge beneath.
Fig. 6—Upper part Trent Valley from Mt. Monotis, showing glacial valley and post-glacial gorge. Trent Saddle is at the upper end of the grass flat at head of valley.

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Fig. 7— [ unclear: ] Valley from 1.000 ft. above Harper Pass, Lake Suinner is Just hidden by right hand side of valley. The depression on the line of the valley beyond Lake Summer marks the Taramakau-Hope Fault.
Fig. 8—Taramakau Valley from 1,000 ft. above Haiper Pass. Taiamakau-Hope Fault piobably follows left hand side of valley to eross spin at the bend as indicated by dashed white line. The Taramakau Fault follows down the valley.

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Fig. 9—Boulder of lower sub-schist at mouth of Warkiti River
Fig. 10—Monotis fossils from Mt. Monotis and Confirmation Rill. Plasticine mould of first fossil found.

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Rahu Survey District). The schist that encloses the ultra-basic rock appears to have about the same rank for the whole length of the ultra-basic belt.