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    Late Quaternary evolution of Matakana Island, Bay of Plenty, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Geography at Massey University
    (Massey University, 1996) Betts, Harley David
    Matakana Island consists of two main parts - an area of mainly Pleistocene materials to the southwest and a c.24 km long Holocene barrier to the northeast. Together with the tombolo systems of Bowentown Heads and Mount Maunganui, Matakana Island encloses the c.200 km² Tauranga Harbour. This study establishes the late Quaternary geomorphological history of Matakana Island, focussing primarily on the evolution of the Holocene barrier. The barrier consists largely of relict foredunes, with relict parabolic dunes, lakes/wetland areas, washover deposits and estuarine flats also present. A detailed geomorphological map provides a foundation for palaeoenvironmental reconstructions. The landform information is supplemented with details of the sedimentology, tephrochronology, pedology, archaeology and palynology of the barrier in order to identify and describe past environmental changes. The Pleistocene part of the island contains remnants of at least three late Pleistocene terraces, mantled by thick beds of tephra and ignimbrite. The lowest terrace, which retains some coastal landforms, originated as a relict foredune plain which probably formed during the Last Interglacial maximum (c.125 000 years ago). The older, higher terraces are likely to have originated during earlier interglacial periods. The barrier consists primarily of moderately well sorted to well sorted medium to fine sand. The dominance of quartz, feldspar and hypersthene indicate that much of the sediment was originally derived from the active Taupo Volcanic Zone. Following the end of the Postglacial Marine Transgression c.7 000 cal BP, deposits of these materials on the continental shelf were reworked and transported shoreward to form the Holocene barrier. Barrier formation commenced by around c.6 000 cal BP. The barrier initially formed in at least two separate parts, separated by a tidal inlet at present-day Blue Gum Bay. The entrance migrated southeastward as the barrier prograded and was closed off c.3 750 cal BP. Following the closure of the entrance, foredunes became larger and more irregular, suggesting a major change to the coastal sediment budget. Progradation rates, calculated from shoreline ages determined by airfall tephra deposits, radiocarbon ages and sea-rafted pumice deposits, generally decreased with time, from about 0.46 metres/year initially to about 0.18 metres/year over the last c.650 years. Significant erosion of the southeastern end of the barrier culminated shortly after the Kaharoa eruption (c.650 cal BP), at which time the barrier was approximately 83 percent of its present length. Subsequently, both ends of the barrier extended rapidly. The coarse texture of sand comprising the barrier ends and anomalously old radiocarbon ages of incorporated shells suggests that, as the entrances narrowed, sediment from adjacent ebb-tidal deltas was reworked to form the barrier ends. The barrier also underwent considerable change following the first arrival of humans on Matakana Island sometime after the Kaharoa eruption. Widespread vegetation clearance and soil disturbance are likely to have contributed to dune instability. Matakana Island appears to have developed in a similar fashion to many Holocene barrier systems of southeastern Australia in terms of a predominant shelf sediment source, onshore sediment transport following the end of the Postglacial Marine Transgression and decreasing progradation rates through time.
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    Are the Northland rivers of New Zealand in synchrony with global Holocene climate change? : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Geography at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Richardson, Jane
    Climate during the Holocene has not been stable, and with predictions of human induced climate change it has become increasingly important to understand the underlying ‘natural’ dynamics of the global climate system. Fluvial systems are sensitive respondents to and recorders of environmental change (including climate). This research integrates meta-data analysis of a New Zealand fluvial radiocarbon (14C) database with targeted research in catchments across the Northland region to determine the influence of Holocene climate change on river behaviour in New Zealand, and to assess whether or not Northland rivers are in synchrony with global climate change. The research incorporates 14C dating and meta-analysis techniques, sedimentology, geophysics, ground survey (RTK-dGPS) and Geographic Information Systems analysis to investigate the response of New Zealand and Northland rivers to Holocene climate and anthropogenic change. The emerging pattern of Holocene river behaviour in New Zealand is one of increased river activity in southern regions (South Island) in response to enhanced westerly atmospheric circulation (promoted by negative Southern Annular Mode [SAM]-like circulation), while in northern regions (North Island) river activity is enhanced by meridional atmospheric circulation (promoted by La Niña-like and positive SAM-like circulation). In Northland, Holocene floodplain development reflects the interplay between valley configuration and accommodation space, sediment supply, fluctuation in climate and anthropogenic factors in the last several hundred years. Evidence from Northland rivers suggests that a globally extensive abrupt climate change signal can promote a synchronous fluvial response, overprinting complex regional patterns of Holocene river behaviour. The research demonstrates that at the centennial-scale, regional atmospheric circulation change is a key driver of river behaviour, with anthropogenic catchment disturbance responsible for enhanced river activity and floodplain aggradation in the last ~ 500 years. It is therefore likely that any future climate change involving a shift in the atmospheric circulation regime will have an impact on river behaviour in New Zealand. However, at the catchment- or reach-scale, river response will be largely determined by local controls such as sediment supply and accommodation space, with these factors largely moderated by the post-settlement fluvial history.
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    Late holocene changes in the vegetation of Western Taranaki investigated by soil palynology : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1987) Lees, Cynthia M
    The study area in western Taranaki is dominated by the andesitic volcano, Mount Egmont.Palynological study of 22 fossil pollen sites from a vide range of sediments has produced evidence of change in vegetation over last 4000 years.The resilience of the indigenous vegetation ensured survival of temperate lowland forests until the arrival of European settlers about 150 years ago.Within this period,deforestation of the lowlands has been almost complete.Surviving forest is protected within Egmont National Park. There is little evidence of pre-European deforestation,but indications of earlier fires are thought to be due to an increase in the Maori diet of Pteridium rhizomes,dictated by a change of climate about 400yr B.P. Information has been gained in general terms about the effects of older tephras and in detail about damage and recovery after tephras deposited within the last 400 years.A revised tephrochronology for the last 400 years is offered. Palynological evidence suggests that an equable climate existed between 4000-1400yr B.P. A decline of Ascarina from very high values at this time to low values at 400yr B.P. has been interpreted as due to a prevalence of droughts.Since 400yr B.P. the climate has been wetter and cooler.This, together with the availability of newly exposed sites due to volcanic activity,has resulted in a dominance of Weinmannia in the Mount Egmont forests. Such dominance is not seen in pollen profiles of older sites over the last 4000 years.
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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.