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    The distribution and properties of soils in relation to erosion in a selected catchment of the southern Ruahine Range, North Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Soil Science at Massey University
    (Massey University, 1978) Hubbard, Carolyn
    The soils of a selected subcatchment of the Southern Ruahine Range have been mapped at a scale of 1:5,000. The soil mapping units have been further characterised by measurement of a number of soil physical and chemical properties, together with an investigation of their sand and clay mineralogies. The erosion history since 20,000 yrs B.P. when the Aokautere Ash was deposited in the West Tamaki River catchment, has been partially reconstructed for this catchment. It is one of erosive periods and resulting aggradational gravel deposits, alternating with more stable periods with soil development and vegetation growth. Studies of a histosol (organic soil) on the summit plateau of the Southern Ruahine Range, at the head of the catchment, suggests that this soil is approximately 4600 years old, and prior to this time the summit plateau was stripped by erosion. Present erosion occurs predominantly: (1) on convex creep slopes, just below the summit plateau, and (2) on the steep valley-sides. In the former zone, where Takapari hill soils exist, deep-seated creep and mass movements occur. In the latter zone, where Ruahine steepland soils exist, superficial soil and rock slips are more common. An investigation of the soil-water relationships for each soil mapping unit indicates that a number of factors render the Takapari hill soils and Ruahine steepland soils particularly susceptible to erosion. A comparison of soil properties which affect the erosion susceptibilities of each soil mapping unit has enabled an ordering of the units with respect to erosion risk. Thus, areas of high, medium and low risk to erosion in the West Tamaki River catchment have been delineated. Many of the deep-seated erosion surfaces occur in The high risk area. Thus, if stabilisation of these sites is possible, by intensive revegetation programmes, the result will be a decrease in the amount of gravels carried out of the mountainland by rivers onto the surrounding fertile floodplains.
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    Determination of procedures to establish priorities for erosion control as determined in the southern Ruahine ranges, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Masterate in Agricultural Science in Soil Science at Massey University
    (Massey University, 1975) Stephens, Peter Robert
    The aim of this study was to investigate several methods of potential usefulness in identifying some of the factors causing erosion in two catchments 'typical' of the southern Ruahine Ranges. The condition of the southern Ruahine Ranges, in the headwaters of the Manawatu River catchment, is deteriorating. The state of equilibrium which has periodically existed between rock, soil, slope, vegetation, and climate has recently been upset, and the area is now in a state of decline. Unless remedial action is taken promptly, farm land will go out of production, public water supplies could be ruined, communications by rail, road, and telephone severely hindered, and the benefits of both the Pohangina-Oroua and Lower Manawatu Flood Control and Drainage Schemes could be lost. This study attempts to establish a basis from which positive steps to rectify the situation can be implemented. Methodology involved the use of aerial photography and on-the-ground observations and measurements. Colour and colour infrared film types were compared with standard black-and-white panchromatic film to establish which was the most suitable to use in determining priorities for erosion control. Sequential panchromatic aerial photographs were taken in 1946, 1961, 1966, and 1974. In this mountainous area, aerial photographs are essential tools for determining the extent of eroded surfaces and erosion types. Between 1946 and 1974 there has been a 120 percent increase in area of eroded slopes in the study area. The worst erosion in 1946, at which time herbivorous mammals had had little effect on vegetation, and in 1974, occurred in the 700 to 900 m altitudinal zone. This zone has the highest fault density in the study area, which consists of densely faulted and mélange-like rocks. This area has also undergone the most dramatic vegetation changes since 1946. Herbivorous mammals are considered to be only partly responsible for such changes. As a corollary, the highest percent increase in erosion has occurred in the altitudinal zone with the most intact vegetative canopy. A positive relationship between the frequency of medium-sized earthquakes and increase of eroded areas has been tentatively established. Further, most erosion has occurred during and following intense rainstorms. These two factors are considered to be the main ones causing erosion in the area. Once factors causing erosion had been established, colour, colour infrared, and panchromatic film types were compared. Photographs used in this comparison were taken periodically throughout 1975 using a 35 mm camera. An assessment was made of the capabilities of each film type to show the following features: alignments, eroded surfaces, erosion types, vegetation types and condition, rock types, pug zones, seepage areas, and drainage pattern. Colour infrared was found to be the most suitable to use when determining priorities for erosion control. A number of salient procedures that should be undertaken to determine priorities for erosion control are outlined. These include aquisition of all sequential photographs, photography using colour infrared, or preferably, using colour infrared and panchromatic film, a sound knowledge of ground conditions, and collation of relevant erosion, geological, botanical, and animal ecological data. A system that enables priority for erosion control of subcatchments to be established, using a rating value for factors causing erosion, is outlined.
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    Late Holocene environmental record and geological history of the Lake Colenso area, north-western Ruahine Range, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Quaternary Science, Soil and Earth Sciences, Institute of Natural Resources, Massey University, Palmerston North, New Zealand
    (Massey University, 2011) MacDonald-Creevey, Amanda Mallory; MacDonald-Creevey, Amanda Mallory
    Sediment cores from a landslide-dammed lake, Lake Colenso (North Island, New Zealand), contain a decadal- to centennial-scale record of changing climate spanning the past 1800 years. A multi-proxy approach has been used to obtain a high-resolution record of variability from the Lake Colenso catchment, and tephra horizons combined with radiocarbon ages provide chronological constraints. Since the lake is located within a mountainous forested catchment of the northern Ruahine Range, it has remained pristine and isolated from human disturbance. Additionally, pollen analysis indicates minimal human influence in the lake catchment; hence the site offers a rare opportunity to investigate natural environmental change during a period in which anthropogenic impact has tended to obscure natural variability in many records from elsewhere in New Zealand (Wilmshurst et al., 1997). Sedimentology and elemental geochemistry reflect periods of rapid sediment influx into the lake, here interpreted as storm events which are preserved at an average of 1 every 150 years. This record, supported by stable isotope records from ostracods, shows distinct periods of increased storminess, and is related to the interaction between regional atmospheric circulation systems, El Niño-Southern Oscillation, Southern Annular Mode and the Pacific Decadal Oscillation. Furthermore, the association with other regional records of climate over the late Holocene highlights the effect of regional climatic forcing. A combination of findings is characterised by broad changes that correlate to the regionally distinctive Medieval Warm Period and Little Ice Age periods, providing further evidence for a climatically variable Holocene (Mayewski et al., 2004). The multi-proxy record presented here is a valuable contribution to existing paleoenvironmental knowledge of the late Holocene in New Zealand. The geology of the study area is characterised by alternating periods of subsidence and uplift throughout the Plio-Pleistocene which resulted in the deposition of Wanganui Basin sediments in the region. Historic earthquake records from nearby major faults are commensurate with ages obtained for landslides at Lake Colenso, which allow a further understanding into landscape evolution and the development of present-day Lake Colenso.
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    Geology and its relationship to erosion in the Southern Ruahine Range, North Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North
    (Massey University, 1984) Marden, Michael
    The structure and lithology of a sequence of Mesozoic greywackes comprising the Torlesse terrane within the southern Ruahine Range has been mapped. At a scale of 1:25 000 the sequence was subdivided into informal lithozones with one or more lithozones constituting a higher order lithostratigraphic unit here referred to as a Lithotype. Each of three recognised Lithotypes occupies a consistent stratigraphic position throughout a 40 km long mapped area. From east to west the three Lithotypes are: (1) the Tamaki Lithotype; (2) the Wharite Lithotype; and (3) the Western Lithotype. The easternmost Tamaki Lithotype and the westernmost Western Lithotype consist of a relatively undeformed flysch-type sequence of distal turbidites. The centrally located wharite Lithotype structurally underlies the Tamaki Lithotype but overlies the Western Lithotype. It comprises a complex sequence of predominantly flysch-type sedimentary rocks, together with lithologically diverse, argillite-dominated, clast-bearing debris flow deposits; large sheet-like bodies of massive volcanics (and associated cherts) that have been emplaced by gravitational sliding; and intact pillow lava accumulations and horizons of red and green argillite of syndepositional origin. Major and trace element analyses of volcanic lithologies indicate that most samples were erupted in a mid-ocean ridge or intraplate setting. None appear to have been derived from an island arc setting. The bulk of the clastic sediments consist of reworked materials derived by the erosion of a mixed volcano-plutonic source and redeposited in a distal deep-water submarine fan environment. Blocks of allochthonous fossiliferous shallow-water lithologies indicate that the source terrane, in part, comprised rocks of Late Triassic age. Autochthonous fossils indicate that sedimentation continued until at least Late Jurassic time. Part of the stratigraphic sequence was severely deformed along a low angle thrust zone in Early Cretaceous time at the onset of the Rangitata Orogeny. An early phase of ductile deformation resulted in plastically and permanently deformed rocks. Ductile deformation is restricted to strata comprising the Wharite Lithotype which, with its allochthonous debris, in part, constitutes an olistostrome that has undergone tectonic deformation and hence also constitutes a melange. Thus it may be regarded as a tectonised olistostrome. Ductile deformation was succeeded by the development of shear fractures during subsequent phases of brittle deformation that affected strata comprising all three Lithotypes. Brittle deformation occurred in conjunction with episodes of faulting and folding during the second orogeny - the Kaikoura Orogeny in Pliocene to Recent times. Active faults that were initiated during the early phase of ductile deformation continued to be sites of active fault displacement throughout Quaternary and Holocene time. Late Quaternary tectonic features along these major active faults have been mapped. Minimum rates of vertical fault displacements since Ohakean time approximate 1 mm/yr in this area. Several phases of folding were recognised, including: (1) an early phase of syndepositional, highly asymmetric folds with well developed axial plane cleavage; and (2) three post-lithification phases of folding - e.g. (a) steeply plunging isoclinal folds; (b) subhorizontal, open asymmetric folds; and (c) steeply plunging open folds. Contacts between the three Lithotypes are not thought to be major tectonic breaks but are instead of primary depositional origin and have become sites of subsequent fault movement in Quaternary time. The three Lithotypes may therefore represent a near complete eastward dipping, westward younging overturned stratigraphic sequence. They are not fault-bound terranes. Metamorphism to prehnite pumpellyite grade, folding and rotation of the strata to its present steep attitude predates Late Cretaceous sedimentation. The westward rotation and imbrication of thrust sheets that are internally westward younging but form part of a regionally eastward younging succession of thrust sheets was the result of underthrusting at a convergent plate margin. The relationship between structural and lithological characteristics of the Torlesse bedrock and the magnitude of valley slope erosion in the southern Ruahine Range is investigated. Comparison of aerial photographs spanning a 28 year period between 1946 and 1974 indicate that erosion has increased by 91%. The greatest proportion of this eroded area occurs on the steeper north- and west-facing slopes. Saturation of colluvium during major storm events is the prime triggering mechanism for the majority of shallow translational slope movements. Debris slides and debris avalanches predominate and result from failure at less than 1m depth at the colluvium-bedrock contact. Rock slides are few in number and are structurally controlled, failing along bedding plane surfaces at greater than 1m depth. Rock falls and rock topples are least numerous and only involve small quantities of material. An erosion rate of 1215m3/ha/yr for the southern Ruahine Range is of the same order of magnitude as other New Zealand and overseas studies and although considered to be severe it is not unduly excessive. Much of the forest deterioration in this area is due to the opening of the canopy by the successive removal of large tracts of forest vegetation through mass movement processes during episodes of increased rainfall. Large-scale rotational and translational mass movement features including rock slumps, earth slumps, earth slides and ridge-top features (involving bedrock only), have been documented from 109 localities. A relationship between the incidence of rock slumps and major fault breccia zones has been established in this area. The majority of large-scale mass movement features failed in pre-historic time but two failed in historic time. The consequences of future mass movements upon lowland areas adjacent to the base of the Range is discussed. A map showing the relative stability of slopes and the predominant forms of slope movement most likely to occur under the present seismic, climatic, physiographic and human conditions is presented