H—34.

Another branch of the Rangitoto Fault (Fault C) diverges westwards to the north of Paeroa, and after running south-west and west-south-west crosses the Manawatu River twice and later reaches the western edge of the Waewaepa greywacke. West of Fault C come marked dip-slopes of Te Aute and Petane beds which give place to a minor syncline and anticline visible in the Manawatu in the vicinity of the Otope Road junction. As a rule the strike of the beds in the region is approximately N. 30° E. The faults are high-angle reverse faults dipping westwards, and tend generally either to follow the direction of strike of the beds or to run suddenly south-west, transverse to the strike. Stratigraphy. Mesozoic (?) Greywackes. —The greywackes of this area are usually indurated, of fine grain and always much weathered. They are cut by joint and shear planes which are covered by thin films of manganese oxides. Bands of fine red chert occur occasionally, and at one locality a thin band of softer yellow mudstones has been observed. No fossils have been found to date. Cretaceous Series. —The Cretaceous, found north and south of the Weber Road near the Mangatuna Road, is represented by chocolate shales, weathering light grey, which enclose large concretions of hard grey limestone with a honey-coloured weathering. These beds distinctly resemble the Waipawa shales. Occasional beds of glauconitic sandstone are enclosed within the beds of shale. Bortonian Series. —Adjoining the Cretaceous rocks are sandy dark-grey mudstones of a facies resembling that of the Ihungia. Pyrite nodules are abundant in some parts of the formation and bands of greensand also occur. The mudstones have yielded a Bortonian microfauna. The thickness is probably between 300 ft. and 500 ft. Ihungia Series. —In the vicinity of the Mangatuna Road junction the Bortonian mudstones pass up into yellow calcareous mudstones which somewhat resemble those of the Weber formation. Dr. Finlay, however, has found that these mudstones contain a microfauna different from that of the Weber and probably representing a special facies fauna of the Lower Ihungia. These calcareous mudstones are not more than 100 ft. or 200 ft. thick. At some localities a sandy limestone band replaces the mudstones, and where present forms a fair marker of the Bortonian-Ihungia boundary. This limestone contains a fauna of pclecypods and abundant corals, which are also to be found in the adjoining mudstones both above and below. At a slightly lower horizon than the coralline limestone there is a similar limestone band containing abundant brachiopods, but this band is less continuous. The Ihungia mudstones above the coralline marker are rather sandy, and there is a passage into the sandstones of the Tutamoe. Tutamoe Series. —The Tutamoe consists of massive soft grey sandstones. Occasional sandy limestone bands have yielded a good fauna including abundant Struthiolaria callosa. The thickness is about 1,200 ft. On the western side of the Cretaceous anticlinal " high " already mentioned a good stratigraphical contact between chocolate shales of the Cretaceous and a sandy limestone with Tutamoe fauna has been observed. The presence of Bortonian on the eastern side of the anticline not far from this contact indicates an extensive overlap of the Tutamoe formation. Mapiri Series. —It has not been possible to separate the Mapiri formation in this region. It is possible that part of the sandstones classified as Tutamoe and Opoiti are of Mapiri age. Opoiti Series. —Soft, grey sandstones resembling the Tutamoe have yielded Opoiti faunas. These sandstones are sometimes finely banded, and bands of shelly limestone occur near their base. One of these bands containing greywacke fragments has occasionally been located at the base of the formation overlying the Tutamoe sandstones. On the western side of Waewaepa Range near Otope Stream a sandy conglomeratic limestone rests in direct stratigraphic contact on the greywackes which present an erosion plane dipping westwards at approximately 20°. The Opoiti Series is usually from 1,000 ft. to 1,300 ft. thick. Te Aute Series. —At the base of the Te Aute Series there is a coarse, sandy, shelly limestone yielding, as a rule, a good fauna. The lower part of the limestone band contains abundant pebbles of sandstone, mudstone, and greywacke. Rarer pebbles of calcareous conglomeratic, worm-bored sandstone are derived from the Opoiti and are evidence of strong local erosion of that formation. The Te Aute limestone band varies from 20 ft. to 50 ft. in thickness, but is, in places, represented by less calcareous and less fossiliferous coarse, yellow sandstones. The limestone band is covered by soft, grey sandstones with an orange, weathered surface. In the eastern part of the region near Oporae the Te Aute appears to be about 1,000 ft. thick, but west of the Waewaepa Range the Te Aute Series attains an approximate thickness of 2,500 ft. and a second limestone band is strongly developed some 500 ft. above the basal limestone. Petane Series. —Petane rocks are similar to those of the Te Aute Series. East of the Waewaepa Range there are three marked limestone bands, ranging in thickness from 30 ft. to 60 ft. and separated by soft grey sandstones; the series is approximately 2,000 ft. thick. West of the Waewaepas there is only one good shelly limestone band, regarded as the base of the formation. There are also some poor local developments of shelly limestone. Between the basal limestone and the Mangatarata beds there is approximately 800 ft. of Petane beds. Mangatarata Series. —The first appearance of white pumiceous sandstones above the Petane beds is regarded as the beginning of the Mangatarata Series, which consists of grey silts and current bedded pumiceous sandstones interbedded with greywacke gravels. Pleistocene and Recent. —The gravels of the high plateau and main terrace are presumably of Pleistocene age. The later gravels of the low terraces are Recent.

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