Overview
Sat. Oct. 11.
Left house at 5.45am on Mr Herd’s bicycle to ascend Rangitoto peak, 1977´, and High Dome (the southern end of Turiri Range) + explore the upper Maharakeke Valley. Cycled up Rangitoto Road – passed school at branch road at 6.am. The margin of the Ruataniwha Plain is here a “cut” surface, the work of the Wharehanga + Poaka Streams, which now flow in incised V-shaped channels. The upper course of the larger Maharakeke is also V-shaped but lower down its trench widens + has a flat bottom. An intricate series of narrow terraces border the Maharakeke, the course if which lies on the built part of the plain, hence the terraces are of gravel. These gravels can be conveniently examined in a gravel-pit alongside the road:- they are for the most part fine, but contain occasional boulders (greywacke and limestone) + there are also small lenticular patches of sand. The gravels are highly fossiliferous + contain Turretilla[?]. Ostria (small species), Dentalium, fragments of branching corals, +c, +c. 1/4pl[ate]. photo (4) of the junction of Maharakeke and a tributary showing terraces + topo. of stream trenches, from roadside south of gravel-pit. Half-a-mile further
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on a road cutting shows some beds of sands capped by limestone. These sands, which in general appearance, hardness +c. are remarkably like the Horowhenua coastal plain sandstones, are grey in colour, current-bedded in places. There are reddish laminae in the grey + also particles of shell. Occasional irreg[uglar] joints leading up to the surface soil and filled with calcareous matter, evidently the wash by rain water from the superjacent limestone, the outcrop of which is characterised by the usual huge blocks. At the point the Maharakeke has no gravel in the sides of its trench, but has cut down through limestone, sands + papa, the last the lowest. Made sketches of the current-bedded sands in cutting. The metalled road ends at a woolshed. The course of the Maharakeke above the woolshed has several striking meanders + here again the stream is bounded by a high gravel terrace, a remote tongue of the Ruataniwha Plain. This area of gravel was deposited (during the building of the Plain) either in a wide part of the original trench or valley of the Maharakeke or perhaps the original valley was wide + gravel-filled throughout its length, the stream since the beginning of rejuvenation having lost its way, deserted its former course in places. + there cut into the papa + other beds of the valley side. The southern end of the
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Oruawharo Ridge lies close by to the west + consists of a linear series of sugar-loaf peaks with the deep trenches of streams between. The formed part of Rangitoto Road ends on the bank of the Maharakeke Stm [Stream] ¾ mile beyond the woolshed. I left the bike here at 7.45 + proceeded on foot up the valley of the large left-bank tributary. In eastern branch of this trib. near junction I noticed a fragment of a fair-sized stalactite among the boulders in the stream bed. The extreme southern end of the Oruawharo Ridge is a very smooth-surfaced razor-backed ridge. I found some rusty-coloured boulders (weathered surfaces) of rock + these proved to be composed of a very hard blue greywacke, the rock of which the Oruawharo Ridge is evidently composed. This was a most surprising discovery. The Oruawharo Ridge is a puzzle – both topographically + lithologically it seems out of place in this Cainozoic formation of monoclinal ridges + (the shaping[?] limestones completed[?] comparatively weak strata. Possibly the rocks of this ridge are of Juna-Triassic age like those of the Ruahines. If so this inlier is at present generally unknown. West of the razor-back ridge, the west branch of the Maharakeke trib. has an incised meandering course in a deep V-shaped gully, in which the high-level narrow
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flood-plain (Ruataniwha Plain level) is quite obliterated by the rejuvenation. Took a photo (1/4pl) from the crest of the razor-back ridge (5) of the Oruawharo sugarloaf peaks. One of Mr. T.G. [?]. Wall’s musterers came up at this junction and was very pleasant giving me some information re[garding] the country +c. Followed the razorback ridge southward to a low transverse ridge, the water-parting between the Maharakeke trib + an affluent of the Waikapiro Stm which flows into the Manawatu River near Ormondville. There are numerous fissures on the hillsides hereabouts, the initial stage in the formation of slips; in one case I noticed that the ground at the lower part of the slipping area was wrinkled up into folds. From the transverse ridge I took a 1/2pl. photo (6) looking north towards the Oruawharo sugarloafs + showing on left part of the east-facing escarpment of a continuous even-crested ridge which lies between the southern end of the Oruawharo Ridge _ the Takapau-Rangitoto limestone ridge, + in foreground head of west branch of Maharakeke trib. Had a snack here at 8.45 + then climbed the unbroken escarpment. Slump topography is well developed on this face which consists of a sandy limestone or calc. [illeg] full small top[?]-shaped gastropods on the crest (dip of this bed seems to be 35° or 40° west); then the current-bedded sands + below this chalk marls (or chalky papa). I turned
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north and followed the low divide between the Waikapiro + Porangahau catchments on to the top of the Takapau or Rangitata or [illegible] Ridge. The southernmost watergap of this ridge lay just north of where I stood. At Rangitoto + for about a mile north, the heavy band of limestone forming the crest of the Takapau Ridge seems to divide into two or more parallel bands. This limestone is a shell rock composed principally of small oysters but I also found two valves of a mollusc of the cockle-type – different sizes but prob[ably]. same species. From the crest of Takapau Ridge I took a 1/2pl. photo (7) (single lens + yellow screen) of the culminating snowy peaks of the Ruahine Range showing southern margin of Ruataniwha Plain in middle distance. Reached the trig stn [station] of Rangitoto at 10.13am – on top + west side is the remains of former heavy matai bush. 1/2pl photo (8) looking north along crest of Takapau ridge showing its backslopes coinciding with dip of limestone strata (22° West), also the Oruawharo Ridge on right, Takapau + Ruataniwha Plain in distance on left, trib of Waikapiro Stm, right foreground, + remarkably even backslope of Rangitoto peak in left foreground. Also ¼ pl. photo (9) of High Dome showing scarp at west end[?], open valley with incised meanders of Waikapiro tributary in foreground. From the summit of Rangitoto a good view of the
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crest-line of the Ruahine Range is obtained. This varies considerably as regards the topography: at the end of the range the crest is somewhat notched into a series of summits of about 3000ft. altitudes, then there is a long stretch of remarkably even sky-line; Opposite Matamau there is a low gap with a surrounding cluster of bush-clad prominences. This is succeeded by a stretch of moderately high peaks with some snow, + opp.[osite] Makeretu the culminating Tumore – Tamatamokuna group of peaks of alpine form with much snow, 5000-5500ft south of Rangitoto and High Dome a topography similar to which [illegible] them continues seemingly right to the Puketois. High Dome has a massive dome-like form when viewed from the west, but structurally it is the western half of a broad anticlinal arch, + is the but slightly dissected culmination of the Turiri Range. Descended eastern face of Rangitoto to junction of head branches of Waikapiro tributary. These streams have cut in their former broad valley-bottom a deep trench characterised by incised meanders and narrowed spurs. 1/4pl. photo (10) of the trench which is cut in blue papa which in places contains patches of scattered bivalve shells, badly preserved + too fragile to extract. Luncyhed here from 10.50-11.15am. The sides of the trench are clothed with a picturesque shrubbery of kowhai, lacey bark, veronica, Panare Coleneir[?], Lance-wood, Manuka, flax,
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totara, etc. The southern end of the continuous even-crested escarpment ends in the forks of these streams. I then ascended the western face of High Dome + gained its broad undulating top which is of immense extent. High Dome was formerly covered with heavy bush (totara etc.) but only on occasional patches remain in some of the gullies – low bush (probably second-growth) clothes some of the slopes. The sources of the Maharakeke + other streams are working back by headward erosion into High Dome but the topography is still immature. On the western part of High Dome the limestone does not crop out on the summit + the rock formation appears to be the sands resting on papa – strike horizontal + the dip gentle towards the west. Further east there is a limestone cap, also a narrow outcrop on northern slope. Descended to junction of headwater streams of Maharakeke, 12.40pm.; they flow in deep Y-shaped gullies cut in blue papa as seen in the gully of the Maharakeke below the junction mentioned above. Sidled round + descended spur to bicycle, arriving at 1.15. Reached the house at 2.30pm. Later in pm. Maud, Alice and I walked to a “washout” on the Maharakeke bank at west end of Mr Herd’s farm. At this spot is the following strata :- soil 6 ins [inches], fine dark-
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brown gravels 5ft., grey to yellowish laminated[?] papa 3ft. blue papa 3ft visible about talus. In the evening Mr Herd + I had a very enjoyable game of chess.