George Leslie Adkin diary entry Sunday 24 August 1919

Sun. Aug. 24.

Weather mild, sky clear + no wind. Left home on horse-back to visit the Mangaharakeke fall, ravine + c on the Poruriri Ridge near Tokomaru, at 5.30 am. From Potts’ old homestead to Shannon the cuttings along the Main Road have been recently widened affording very clear sections of the sandstone

[new page]

formation. At Potts’ cutting the sandstone (not visible) is capped by more than four or five feet of stained gravel which is overlain by 10ft or so of yellow clay jointed vertically into rude columns. This is probably a high-level deposit of the Waoku Stream. Just north of the "height of road" on Ihakara’s Reserve a section of the sandstone formation shoes interbedded seams, one to 2ft thick, of light grey + bluish clay with several feet of grey sandstone on top. Further on there are thin layers of jointed sandstone interbedded with unjointed sandstone + with clayey [sic] seams. Dark laminae are conspicuous in many places, + with one exception between "height of road + intersection of Buckly Rd. At one place the laminae showed cross-bedding. Pseudo-stratification, in the form of horizontal or oblique lines, thin bands of broken lines of hy[drogen] peroxide of iron, occurs in several places. Passed Shannon rly stn [Railway Station] at 6.56 am. North of Shannon I examined the road cutting in which I previously noted greywacke pebbles imbedded in the sandstone. These occur in a narrow bed, a few inches thick, in only one place. The pebbles a [sic] small, none exceeding one inch in diameter. In the sandstone above this seam are numbers of very tiny scattered pebbles. The spot seems to mark the course of a very gently flowing stream which was depositing as the land sank to it’s [sic] minimum

[new page]

elevation in the Middle Pleistocene. Between the Mangaone Stream + Makerua rly. Stn. the Main Road runs alongside the railway, and along this stretch, spurs or promontories of the sandstone formation reach nearly to the road. The formation appears to have been truncated hereabouts (since it certainly formerly extended further west) by the Manawatu River when that mighty stream occupied + meandered on the site of the present Makurerua Swamp. Between the sandstone spurs mentioned above are the gullies of steams rising in the Tararua foothills or on the upper (easterly[?]) part of the sandstone upland. The gullies are flat-bottomed + usually swampy + increase in width as they extend westward. Off the ends of some of the sandstone spurs are isolated mounds of buttes of sandstone – isolated by the alternate lateral corrosion [?] of streams in the neighbouring gullies when they were in a more active state than at present. The swampy gully-bottoms merge into the great Makurerua Swamp which stretches for miles on the western side of the rly line. Reached Makerua rly stn at 7.27 + set aneroid at 22'. At this point the road leaves the rly. Line + runs inland across the spurs of, + gullies in, the sandstone formation. The western slope of the Poruriri Ridge is well seen

[new page]

From here – it has lateral spurs with blunted ends at its southern end but further north it presents an almost unbroken truncated face. From the foot of several of the main gullies situated in the latter section, a number of rather conspicuous fans of alluvium slope westward. From the lower margin of these fans the hill streams flow in the gullies cut in the sandstone formation. In addition to theses there is a fairly extensive swamp heading[?] in the sandstone formation, + surrounded by much gentler slopes than those that bound the gullies containing the streams from the hills – surrounded in fact by quite a mature topography. North of the junction of Victoria Road, aneroid 10', 7.45, there are dry floodplains in the gully-bottoms on the east side of road but on the west side these become swampy as they merge into the Makurerua Swamp. The flood-plain of the Mangaharakeke Stream is, however, dry + grassy for some distance west of the line of the Main Rod + this dry area extends north-west to the Tokomaru River. This area is probably a fan deposit (of fairly recent date) of the Tokomaru River, or may possibly be the lower part of the Early Pleistocene fan of the Tokomaru River. Reached Albert Road junction at 8.19 aneroid 8'. Turned up albert Road + from edge of sandstone upland overlooking gully of Mangaharakeke Stream just below the junction of its

[new page]

larger right-bank tributary took a panoramic ¼ pl[ate] photo (1+2) of the western face of Poruriri Ridge showing the Mangaharakeke ravine + Pouriri Ridge showing trig[.] Rode to end of Albert Road mapping topography as I went. At end there is the old mill which formerly cut the timber cut in upper basin of Mangaharakeke. Tied up horse near foot of the ravine stream at outlet of ravine 263° (corrected 260°) 9pm. From the foot of the ravine, the Mangaharakeke has cut a straight deep gully (in the sandstone formation) the bottom of which is extremely stony + flood-swept at foot of the hills but smoother further down. At foot of ravine are the remains of stony fans of detritus swept out of the ravine in the past + now incised + fragmentary. On the south side of the M[angaharakeke] ravine is the deepest of the minor gullies of the steep face of the Poruriri Ridge. It junctions with the M. at the lower end of the ravine – hence its greater depth than the other minor gullies. I ascended the face of Pouriri Ridge via of truncated spur + the upper part of the tributary gully to the head of the M. ravine, looking down into it from a point a few chains south-west of the main fall. The sides of the ravine right to its head are sheer + slippery, the upper limit of the precipices being a distinctly

[new page]

marked line. The main fall, as noted on my previous visit, descends the 300ft. of its height down a sheer precipice, the foaming water being divided into three leaps by very narrow rock-ledges. There is no doubt as to the very recent excavation of this ravine., its form being one of extreme youth, as shown by the precipitous slippery rocky sides + narrow ungraded bottom. The sudden spilling over of a fair-sized stream like the Mangaharakeke, liberated an enormous amount of erosive power with the result that the frontally deeply truncated spurs on either side of the ravine were shorn away longitudinally, leaving them as half-spurs, i.e. having a concave precipice on the one side + the normal form on the other. The spurs enclosing the neighbouring minor gullies do no [sic] possess a similar configuration, a fact further emphasizing the special origin of the ravine. Crest of Mangaharakeke Fall 1027' (1020') 9.34. Above the fall the M. + its small tributaries flow in narrow youthful bunches[?] incised to a depth of about 120 ft. in the western part of the former alluvial flat. Top of westernmost (+ slightly lowered) part of alluvial flat 1158' (1152') 9.50. summit of original level of old alluvial flat (almost 8 ch[ai]ns east of last) 1175' (1168') 10.pm. The alluvial flat is built up of fine stained gravels

[new page]

capped with a few feet of yellow clay. Considered as a single unit, the former + present catchment areas of the Mangaharakeke Stream have a topographic form intermediate between that of the Waireka Stream + that at "The heights". It is a bottle-necked valley with it's original outlet leading eastward to the upper Tokomaru Valley heading in the main Poruriri divide near Poruriri trig + bounded on north + south by long high lateral spurs. As shown by remaining fragments, the whole alluvial flat sloped gently eastward until by the excessive alluviation of the upper part of it's course, the Mangaharakeke escaped over the main divide, beheading itself and taking a spill-over course down the western slope of the Poruriri Ridge. The largest patch of original alluvial flat is bounded on the east by a bank about 20ft in height + east of this the old trunk drainage still drains the lower end of the bottle-necked aggrated valley. This part of the drainage has been rejuvenated – it first cut downwards to a depth of 25 ft or so, then widened to channels + formed a broad flat similar to the upper one, + finally became winding + sluggish again; this is its present state. At the lower end of the valley, however,

a deep gully appears to be working back into the second flat from the Tokomaru River + another period of rejuvenation seems to be commencing. The former M. valley is divided transversely by the boundary fence between two farms- in the upper (western) a fine flock of breeding ewes were lambing (+ dying from neglect) + in the other a large herd of well-bred steers were grazing. I ascended to the crest of the north lateral spur on which is situated a small whare, + nearby some food cattle-y[ar]ds. At cattle-yards, 1247° (1240°) 10.15. From this main lateral spur of the Pouriri Ridge, little side spurs run down to the forge of the Tokomaru River- their slope is a first fairly gentle, then there is a sort of ledge, + below this very steep slope drops into the gorge followed the lateral spur to a high knob overlooks the sharp bend in the Tokomaru River. High knob 1487° (1478°) 10.35. Took a panoramic photo (3+4) of the upper part of the bottle-necked former valley of the Mangaharakeke Stream. A good view of the upper Tokomaru Valley + the Tararua peaks is to be had from here + today the weather was very favourable. To the east I could distinguish the sub-alpine scrub-clad peaks of Arawaru, Scrub + Mairakau; to the south of the Dundas