title: Holocene vegetation and volcanic activity, Auckland Isthmus, New Zealand

authors: Newnham, Rewi M.

subjects: palynology

abstract: A 12 000 to 4000 yr BP pollen and tephra-bearing profile from Auckland, New Zealand, provides insights into the vegetation history and evidence for early Holocene volcanic activity in this area centred on the Mount Wellington basaltic volcano. Possibly 500 yr separated initial scoriaceous ash deposition (ca. 9500 yr ago) and subsequent major lava flows (ca. 9000 yr ago) from Mount Wellington. The local vegelation, topography, and drainage patterns were substantially modified during this time, and damming by the lava flows resulted in the formation of Lake Waiatarua in a shallow valley head ca. 9000 yr ago. Diatom evidence indicates that this lake was initially deep (> 5 m) but was shallowing around 4000 yr ago. In contrast to the Mount Wellington eruptions, tephra deposition resulting from distant rhyolitic volcanic activity of the central North Island and Mayor Island has had little effect on the Auckland vegetation during this time interval (12 000–4000 yr ago).
Between ca. 12 000 and 10 000 yr ago, conifer-angiosperm forest was the predominant vegetation cover on Auckland Isthmus, but during the early Holocene, forest dominated by Metrosideros expanded, probably on to fresh volcanic surfaces resulting from the Mount Wellington eruptions. At this time, swamp forest communities developed in Waiatarua valley basin, and included species indicative of moist, mild, relatively frost-free climates. Some taxa show histories consistent with other records from the northern New Zealand region, including the rise of Ascarina lucida ca. 11 000 to 9000 yr ago, and its subsequent decline, and the expansion of Agathis australis (kauri) forest communities from ca. 6000 yr ago. Taken together the history of local and regional vegetation points to a mild, moist and weakly seasonal early Holocene climate, which subsequently became drier with greater seasonal temperature extremes.

text: Holocene vegetation and volcanic activity, Auckland Isthmus, New Zealand A 12 000 to 4000 yr BP pollen and tephra-bearing profile from Auckland, New Zealand, provides insights into the vegetation history and evidence for early Holocene volcanic activity in this area centred on the Mount Wellington basaltic volcano. Possibly 500 yr separated initial scoriaceous ash deposition (ca. 9500 yr ago) and subsequent major lava flows (ca. 9000 yr ago) from Mount Wellington. The local vegelation, topography, and drainage patterns were substantially modified during this time, and damming by the lava flows resulted in the formation of Lake Waiatarua in a shallow valley head ca. 9000 yr ago. Diatom evidence indicates that this lake was initially deep (> 5 m) but was shallowing around 4000 yr ago. In contrast to the Mount Wellington eruptions, tephra deposition resulting from distant rhyolitic volcanic activity of the central North Island and Mayor Island has had little effect on the Auckland vegetation during this time interval (12 000–4000 yr ago).
Between ca. 12 000 and 10 000 yr ago, conifer-angiosperm forest was the predominant vegetation cover on Auckland Isthmus, but during the early Holocene, forest dominated by Metrosideros expanded, probably on to fresh volcanic surfaces resulting from the Mount Wellington eruptions. At this time, swamp forest communities developed in Waiatarua valley basin, and included species indicative of moist, mild, relatively frost-free climates. Some taxa show histories consistent with other records from the northern New Zealand region, including the rise of Ascarina lucida ca. 11 000 to 9000 yr ago, and its subsequent decline, and the expansion of Agathis australis (kauri) forest communities from ca. 6000 yr ago. Taken together the history of local and regional vegetation points to a mild, moist and weakly seasonal early Holocene climate, which subsequently became drier with greater seasonal temperature extremes.

year: 1991

title: The Fault in our Hill: Characterisation of the Rangitawa Tephra, and insight into tectonic influences at Hillcrest Road

authors: Gibbons, Vittoria

subjects: Tephra

abstract: This study aimed to identify deformation and characterise the Rangitawa Tephra in terms of geomechanical and geochemical properties, and relate these properties to the deformation potential/activity. It was hypothesised there is a fault present in the site at 59 Hillcrest Road, and that the Rangitawa Tephra deforms plastically and accommodates deformation thereby reducing the amount of deformation in the geological units above.  

Field analyses included stratigraphic observations, unit descriptions, structural observations and anomaly identification, sensitivity measurements, and description of soft sediment deformation structures. Laboratory analyses consisted of particle-size, mineralogy, chemistry, and microstructure analyses and geomechanical behaviour identification through Atterberg Limits and Triaxial shear testing. 

Field analyses showed the presence of soft sediment deformation in the form of offset and deformed bedding at the base of the Rangitawa Tephra unit, and in the Hamilton Ash Formation above, along with a significant offset of approximately 6 metres within the cutting at 59 Hillcrest Road. This is inferred to be a normal fault, with the surrounding deformation seismites resulting from seismic triggers in the area along this fault plane. 

Laboratory analyses were used to characterise the Rangitawa Tephra at Hillcrest Road based on geomechanical, chemical, and mineralogical properties indicated the Rangitawa is bimodal extra-fine silt and extra-fine sand with an average of medium silt texture, behaving as a low compressibility silt. The clay mineralogy present as halloysite, dehydrated in Atterberg Limits testing, but hydrated otherwise. Triaxial shear testing identified the Rangitawa Tephra at Hillcrest to be of normally consolidated material, exhibiting ductile-plastic characteristics. The properties indicated during laboratory analyses were used to provide explanations for the deformation structures observed in the exposure at 59 Hillcrest Road. Field analyses along with the laboratory characterisation of the Rangitawa Tephra confirm the presence of a fault plane at the exposure. 


The thesis concludes the Rangitawa Tephra exhibits plastic deformation characteristics, presenting the potential to exhibit cyclic softening. These findings confirm the presence of ductile displacement, and support the soft sediment deformation structures observed at the base of the Rangitawa Tephra, and in the Hamilton Ash formation, are the direct result of paleoseismic influences within the area. It can then be suggested this fault zone may be active (displacement younger than 100 ky.) (GNS, 2017). The ductile plastic characteristics of the Rangitawa Tephra suggests deformation within and above this unit could be present, masked by the atypical displacement features and reduced by the accommodated deformation by the Rangitawa Tephra, suggesting the inferred ages on other faults found within the basin may be much younger than expected.

text: The Fault in our Hill: Characterisation of the Rangitawa Tephra, and insight into tectonic influences at Hillcrest Road This study aimed to identify deformation and characterise the Rangitawa Tephra in terms of geomechanical and geochemical properties, and relate these properties to the deformation potential/activity. It was hypothesised there is a fault present in the site at 59 Hillcrest Road, and that the Rangitawa Tephra deforms plastically and accommodates deformation thereby reducing the amount of deformation in the geological units above.  

Field analyses included stratigraphic observations, unit descriptions, structural observations and anomaly identification, sensitivity measurements, and description of soft sediment deformation structures. Laboratory analyses consisted of particle-size, mineralogy, chemistry, and microstructure analyses and geomechanical behaviour identification through Atterberg Limits and Triaxial shear testing. 

Field analyses showed the presence of soft sediment deformation in the form of offset and deformed bedding at the base of the Rangitawa Tephra unit, and in the Hamilton Ash Formation above, along with a significant offset of approximately 6 metres within the cutting at 59 Hillcrest Road. This is inferred to be a normal fault, with the surrounding deformation seismites resulting from seismic triggers in the area along this fault plane. 

Laboratory analyses were used to characterise the Rangitawa Tephra at Hillcrest Road based on geomechanical, chemical, and mineralogical properties indicated the Rangitawa is bimodal extra-fine silt and extra-fine sand with an average of medium silt texture, behaving as a low compressibility silt. The clay mineralogy present as halloysite, dehydrated in Atterberg Limits testing, but hydrated otherwise. Triaxial shear testing identified the Rangitawa Tephra at Hillcrest to be of normally consolidated material, exhibiting ductile-plastic characteristics. The properties indicated during laboratory analyses were used to provide explanations for the deformation structures observed in the exposure at 59 Hillcrest Road. Field analyses along with the laboratory characterisation of the Rangitawa Tephra confirm the presence of a fault plane at the exposure. 


The thesis concludes the Rangitawa Tephra exhibits plastic deformation characteristics, presenting the potential to exhibit cyclic softening. These findings confirm the presence of ductile displacement, and support the soft sediment deformation structures observed at the base of the Rangitawa Tephra, and in the Hamilton Ash formation, are the direct result of paleoseismic influences within the area. It can then be suggested this fault zone may be active (displacement younger than 100 ky.) (GNS, 2017). The ductile plastic characteristics of the Rangitawa Tephra suggests deformation within and above this unit could be present, masked by the atypical displacement features and reduced by the accommodated deformation by the Rangitawa Tephra, suggesting the inferred ages on other faults found within the basin may be much younger than expected.

year: 2020

title: Enacting Kaitiakitanga Challenges and Complexities in the Governance and Ownership of Rongoā Research Information.

authors: Boulton, Amohia

subjects: Indigenous

abstract: This article explores the tensions one research team has faced in securing appropriate governance or stewardship (which we refer to as kaitiakitanga) of research data. Whilst ethical and regulatory frameworks exist which provide a minimum standard for researchers to meet when working with Māori, what our experience has highlighted is there is currently a “governance” gap in terms of who should hold stewardship of research data collected from Māori individuals or collectives. In the case of a project undertaken in the traditional healing space, the organisation best placed to fulfil this governance role receives no funding or support to take on such a responsibility; consequently by default, this role is being borne by the research team until such time as capacity can be built and adequate resourcing secured. In addition, we have realised that the tensions played out in this research project have implications for the broader issue of how we protect traditional knowledge in a modern intellectual property law context, and once again how we adequately support those, often community-based organisations, who work at the interface between Indigenous knowledge and the Western world.

text: Enacting Kaitiakitanga Challenges and Complexities in the Governance and Ownership of Rongoā Research Information. This article explores the tensions one research team has faced in securing appropriate governance or stewardship (which we refer to as kaitiakitanga) of research data. Whilst ethical and regulatory frameworks exist which provide a minimum standard for researchers to meet when working with Māori, what our experience has highlighted is there is currently a “governance” gap in terms of who should hold stewardship of research data collected from Māori individuals or collectives. In the case of a project undertaken in the traditional healing space, the organisation best placed to fulfil this governance role receives no funding or support to take on such a responsibility; consequently by default, this role is being borne by the research team until such time as capacity can be built and adequate resourcing secured. In addition, we have realised that the tensions played out in this research project have implications for the broader issue of how we protect traditional knowledge in a modern intellectual property law context, and once again how we adequately support those, often community-based organisations, who work at the interface between Indigenous knowledge and the Western world.

year: 2014