title: Using paleoseismology and tephrochronology to reconstruct fault rupturing and hydrothermal activity since c. 40 ka in Taupo Rift, New Zealand

authors: Loame, Remedy C.

subjects: Science & Technology

abstract: The Taupo Volcanic Zone (TVZ) in North Island, New Zealand, is the on-land continuation of the Tonga-Kermadec arc formed in the Quaternary at the obliquely convergent boundary of the Pacific and Australian tectonic plates. The central TVZ is a region of intense silicic volcanism and active rifting with a very high heat flux. Within this zone is a dynamic landscape affected by a dense, active fault network, the Taupo Rift. In this rift, the Ngakuru graben hosts fossil hydrothermal systems in an area parallel to numerous active faults including the east strand of Whirinaki Fault that forms a major structure. Using various geoscientific techniques including mapping, stratigraphy, paleoseismic trenching, and tephrostratigraphy, in conjunction with LiDAR-derived DEMs, we reconstruct and date the fault's rupture history along with hydrothermal activity (including silica-sinter development) since c. 40,000 calendar years ago (40 cal. ka) at a site near Hossack Road called “Meade”. Ages for Kawakawa (c. 25.4 cal. ka), Okareka (c. 21.8 cal. ka), Rotorua (c.15.6 cal. ka), Rotoma (c. 9.4 cal. ka), and Taupo (c. 1.7 cal. ka) tephras enabled us to date five identified fault rupture events using the Meade trench excavation. Slip rates of 2.66 ± 0.77 mm/yr (pre-Kawakawa tephra), 0.28 ± 0.04 mm/yr (between c. 25.4 ka and Taupo) and 0.51 ± 0.19 mm/yr (post-Taupo), and the recurrence interval of ∼5500 cal. yr during the last c. 25.4 cal. kyr, all correlate with events of similar ages determined from studies on other trenches on Whirinaki Fault. Intercalated with Tahuna tephra (c. 39.3 cal. ka) and additionally dated at c. 38.9 cal. ka using radiocarbon, the hydrothermal sinter began developing at the Meade site at c. 39 cal. ka and ceased by c. 21.8 cal. ka (marked by Okareka tephra). We examine the causative relationship between fault activity and the development of sinter by comparing the chronology of volcanic eruptions and fault rupturing events with that of sinter formation as recorded in three neighbouring sites, Mangatete, Matthews, and Fitzpatrick. The findings improve understanding of the complex rupture behaviour of faulting and provide evidence for relationships between tectonic and hydrothermal activities, which were additionally influenced by the impacts of climatic change and geomorphic processes on landscape evolution, within the late Quaternary period. The study also exemplifies the unique value of tephrochronology in helping to disentangle complex geological deposits and events in an extremely dynamic part of the Earth's surface (the Taupo Rift).

text: Using paleoseismology and tephrochronology to reconstruct fault rupturing and hydrothermal activity since c. 40 ka in Taupo Rift, New Zealand The Taupo Volcanic Zone (TVZ) in North Island, New Zealand, is the on-land continuation of the Tonga-Kermadec arc formed in the Quaternary at the obliquely convergent boundary of the Pacific and Australian tectonic plates. The central TVZ is a region of intense silicic volcanism and active rifting with a very high heat flux. Within this zone is a dynamic landscape affected by a dense, active fault network, the Taupo Rift. In this rift, the Ngakuru graben hosts fossil hydrothermal systems in an area parallel to numerous active faults including the east strand of Whirinaki Fault that forms a major structure. Using various geoscientific techniques including mapping, stratigraphy, paleoseismic trenching, and tephrostratigraphy, in conjunction with LiDAR-derived DEMs, we reconstruct and date the fault's rupture history along with hydrothermal activity (including silica-sinter development) since c. 40,000 calendar years ago (40 cal. ka) at a site near Hossack Road called “Meade”. Ages for Kawakawa (c. 25.4 cal. ka), Okareka (c. 21.8 cal. ka), Rotorua (c.15.6 cal. ka), Rotoma (c. 9.4 cal. ka), and Taupo (c. 1.7 cal. ka) tephras enabled us to date five identified fault rupture events using the Meade trench excavation. Slip rates of 2.66 ± 0.77 mm/yr (pre-Kawakawa tephra), 0.28 ± 0.04 mm/yr (between c. 25.4 ka and Taupo) and 0.51 ± 0.19 mm/yr (post-Taupo), and the recurrence interval of ∼5500 cal. yr during the last c. 25.4 cal. kyr, all correlate with events of similar ages determined from studies on other trenches on Whirinaki Fault. Intercalated with Tahuna tephra (c. 39.3 cal. ka) and additionally dated at c. 38.9 cal. ka using radiocarbon, the hydrothermal sinter began developing at the Meade site at c. 39 cal. ka and ceased by c. 21.8 cal. ka (marked by Okareka tephra). We examine the causative relationship between fault activity and the development of sinter by comparing the chronology of volcanic eruptions and fault rupturing events with that of sinter formation as recorded in three neighbouring sites, Mangatete, Matthews, and Fitzpatrick. The findings improve understanding of the complex rupture behaviour of faulting and provide evidence for relationships between tectonic and hydrothermal activities, which were additionally influenced by the impacts of climatic change and geomorphic processes on landscape evolution, within the late Quaternary period. The study also exemplifies the unique value of tephrochronology in helping to disentangle complex geological deposits and events in an extremely dynamic part of the Earth's surface (the Taupo Rift).

year: 2019

title: Effects of cortisol on female-to-male sex change in a wrasse

authors: Goikoetxea, Alexander

abstract: Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.

text: Effects of cortisol on female-to-male sex change in a wrasse Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.

year: 2022

title: "That's the price we pay": Kaupapa Māori Programme stakeholder experiences of external evaluation

authors: Masters-Awatere, Bridgette

subjects: Evaluation

abstract: This thesis takes a critical approach to the evaluation of Māori social and health service provision progammes through an in-depth exploration of the dynamics, impacts and politics of such exercises within Māori communities, and upon relationships between Māori and the Crown, and its agents. Since the mid 1980s, New Zealand government devolved responsibilities that heralded a change in economic focus and provided a pathway for targeted service provision, such as social and health programmes, amongst communities. The combined shift to Neoliberal economics and the virtual hegemony enjoyed by right wing economic commentators, policy-makers and business leaders meant that newly anointed Māori service providers were not fully prepared for the subsequent rise in demand for narrowly defined accountability requirements that did not reflect Māori aspirations or values.

This study sought to critically engage with the experiences of stakeholders affected by an external evaluation of “By Māori, for Māori” services. Qualitative data capturing stakeholder narratives, demonstrated the complex relationships and range of emotions experienced by programme stakeholders. Four case studies contain stories that highlight: service provider relationships built on betrayal that contributed to programme tensions and influenced the design of the evaluation; different stakeholder information needs that shaped their expectation of an evaluation; service provider vulnerability when implementing cultural values with their funder, who then seeks financial gain from that knowledge, and; the close links of Kaupapa Māori programmes and their evaluations to socio-cultural and political agendas.

The cases highlight ways Māori evaluators operated from a reflexive approach that recognised two worldviews (Mātauranga Māori and the dominant models of Western social science) and sought to facilitate engaged evaluation relationships with different stakeholders. A proposed Cultural Confluent Evaluation model lays out the dynamics and tensions in an attempt to make visible the underlying agendas, but also the glossed ideologies of power and control attached to conventional evaluations. As existing programmes continue to be examined for their cultural responsiveness, and as new culturally-centred programmes are proposed, the need for culturally embedded evaluation is even more evident.

text: "That's the price we pay": Kaupapa Māori Programme stakeholder experiences of external evaluation This thesis takes a critical approach to the evaluation of Māori social and health service provision progammes through an in-depth exploration of the dynamics, impacts and politics of such exercises within Māori communities, and upon relationships between Māori and the Crown, and its agents. Since the mid 1980s, New Zealand government devolved responsibilities that heralded a change in economic focus and provided a pathway for targeted service provision, such as social and health programmes, amongst communities. The combined shift to Neoliberal economics and the virtual hegemony enjoyed by right wing economic commentators, policy-makers and business leaders meant that newly anointed Māori service providers were not fully prepared for the subsequent rise in demand for narrowly defined accountability requirements that did not reflect Māori aspirations or values.

This study sought to critically engage with the experiences of stakeholders affected by an external evaluation of “By Māori, for Māori” services. Qualitative data capturing stakeholder narratives, demonstrated the complex relationships and range of emotions experienced by programme stakeholders. Four case studies contain stories that highlight: service provider relationships built on betrayal that contributed to programme tensions and influenced the design of the evaluation; different stakeholder information needs that shaped their expectation of an evaluation; service provider vulnerability when implementing cultural values with their funder, who then seeks financial gain from that knowledge, and; the close links of Kaupapa Māori programmes and their evaluations to socio-cultural and political agendas.

The cases highlight ways Māori evaluators operated from a reflexive approach that recognised two worldviews (Mātauranga Māori and the dominant models of Western social science) and sought to facilitate engaged evaluation relationships with different stakeholders. A proposed Cultural Confluent Evaluation model lays out the dynamics and tensions in an attempt to make visible the underlying agendas, but also the glossed ideologies of power and control attached to conventional evaluations. As existing programmes continue to be examined for their cultural responsiveness, and as new culturally-centred programmes are proposed, the need for culturally embedded evaluation is even more evident.

year: 2015