title: Sub-millennial eruptive recurrence in the silicic Mangaone Subgroup tephra sequence, New Zealand, from Bayesian modelling of zircon double-dating and radiocarbon ages

authors: Danišík, Martin

subjects: Zircon double-dating

abstract: Accurate dating of young (<1 Ma) volcanic eruptions has long been a challenge for modern geochronology given the scarcity of datable mineral phases and low quantities of radiogenic daughter products. Combined U-Th-Pb and (U-Th)/He dating of zircon (i.e., zircon double-dating, ZDD) is a relatively new dating approach that offers a viable option for dating zircon-bearing volcanic and pyroclastic deposits as young as ca. 3 ka, and has a great potential for application in many fields within the Quaternary sciences, including volcanology, palaeoclimatology, and archaeology. In our study, a stratigraphically and spatially well-defined sequence of 13 rhyodacitic to rhyolitic tephra beds e the Mangaone Subgroup (MSg) erupted from the Okataina Volcanic Centre (OVC), is used as a natural laboratory to conduct a crossvalidation experiment in which the ZDD eruption ages are compared with published and new radiocarbon (¹⁴C) eruption ages. These ZDD and ¹⁴C ages are then used together to underpin a Bayesian age model developed (using ChronoModel) to provide new ages for the entire MSg sequence. New ZDDeruption ages of 36.1 ± 4.4, 31.5 ± 5.2, 30.9 ± 5.6, 31.2 ± 4.4 ka BP for four MSg tephras (Units D, I, J, and K, respectively) are statistically indistinguishable from ¹⁴C-based eruption ages. These results validate the feasibility of ZDD to date late Quaternary eruptions accurately. The Bayesian age sequence model provides provides an eruptive geochronology eruptive geochronology for all 13 MSg tephra beds for the first time (and for the stratigraphically-interbedded Taupo-volcano-derived Tahuna tephra, 38.4 ⁺¹.⁷ ₋₁.₄ ka BP), and constrains the beginning of the MSg eruption period to 42.7 ⁺³.⁷₋₃.₅ ka BP (Unit A) and the end to 30.6 ⁺⁰.⁶₋₁.₅ ka BP (Unit L). Thus, the entire MSg sequence was emplaced in ~12,100 years, representing an eruption frequency of one event per ~930 years on average. Our study demonstrates the efficacy of ZDD to yield accurate eruption ages on pyroclastic deposits, highlighting its potential for dating young (<1 Ma) magmatic and eruption events that are difficult to date by other geochronological methods, and also shows that ZDD dates can be integrated with ¹⁴C ages using Bayesian modelling to develop new age models for long sequences of tephra beds, in this case those of the MSg tephras that were deposited during MIS 3. In addition, the U-Th zircon crystallization data revealed distinct U-Th model age spectra for older and younger MSg tephras, providing geochronological evidence for decreasing degree of interconnectedness within the OVC magma reservoir during the MSg eruption period that followed caldera collapse associated with the pre-MSg Rotoiti (Rotoehu) eruption at ca. 45 ka BP.

text: Sub-millennial eruptive recurrence in the silicic Mangaone Subgroup tephra sequence, New Zealand, from Bayesian modelling of zircon double-dating and radiocarbon ages Accurate dating of young (<1 Ma) volcanic eruptions has long been a challenge for modern geochronology given the scarcity of datable mineral phases and low quantities of radiogenic daughter products. Combined U-Th-Pb and (U-Th)/He dating of zircon (i.e., zircon double-dating, ZDD) is a relatively new dating approach that offers a viable option for dating zircon-bearing volcanic and pyroclastic deposits as young as ca. 3 ka, and has a great potential for application in many fields within the Quaternary sciences, including volcanology, palaeoclimatology, and archaeology. In our study, a stratigraphically and spatially well-defined sequence of 13 rhyodacitic to rhyolitic tephra beds e the Mangaone Subgroup (MSg) erupted from the Okataina Volcanic Centre (OVC), is used as a natural laboratory to conduct a crossvalidation experiment in which the ZDD eruption ages are compared with published and new radiocarbon (¹⁴C) eruption ages. These ZDD and ¹⁴C ages are then used together to underpin a Bayesian age model developed (using ChronoModel) to provide new ages for the entire MSg sequence. New ZDDeruption ages of 36.1 ± 4.4, 31.5 ± 5.2, 30.9 ± 5.6, 31.2 ± 4.4 ka BP for four MSg tephras (Units D, I, J, and K, respectively) are statistically indistinguishable from ¹⁴C-based eruption ages. These results validate the feasibility of ZDD to date late Quaternary eruptions accurately. The Bayesian age sequence model provides provides an eruptive geochronology eruptive geochronology for all 13 MSg tephra beds for the first time (and for the stratigraphically-interbedded Taupo-volcano-derived Tahuna tephra, 38.4 ⁺¹.⁷ ₋₁.₄ ka BP), and constrains the beginning of the MSg eruption period to 42.7 ⁺³.⁷₋₃.₅ ka BP (Unit A) and the end to 30.6 ⁺⁰.⁶₋₁.₅ ka BP (Unit L). Thus, the entire MSg sequence was emplaced in ~12,100 years, representing an eruption frequency of one event per ~930 years on average. Our study demonstrates the efficacy of ZDD to yield accurate eruption ages on pyroclastic deposits, highlighting its potential for dating young (<1 Ma) magmatic and eruption events that are difficult to date by other geochronological methods, and also shows that ZDD dates can be integrated with ¹⁴C ages using Bayesian modelling to develop new age models for long sequences of tephra beds, in this case those of the MSg tephras that were deposited during MIS 3. In addition, the U-Th zircon crystallization data revealed distinct U-Th model age spectra for older and younger MSg tephras, providing geochronological evidence for decreasing degree of interconnectedness within the OVC magma reservoir during the MSg eruption period that followed caldera collapse associated with the pre-MSg Rotoiti (Rotoehu) eruption at ca. 45 ka BP.

year: 2020

title: A comparison of methods for estimating prediction intervals in NIR spectroscopy: Size matters

authors: Bouckaert, Remco R.

subjects: NIR

abstract: In this article we demonstrate that, when evaluating a method for determining prediction intervals, interval size matters more than coverage because the latter can be fixed at a chosen confidence level with good reliability. To achieve the desired coverage, we employ a simple non-parametric method to compute prediction intervals by calibrating estimated prediction errors, and we extend the basic method with a continuum correction to deal with small data sets. In our experiments on a collection of several NIR data sets, we evaluate several existing methods of computing prediction intervals for partial least-squares (PLS) regression. Our results show that, when coverage is fixed at a chosen confidence level, and the number of PLS components is selected to minimize squared error of point estimates, interval estimation based on the classic ordinary least-squares method produces the narrowest intervals, outperforming the U-deviation method and linearization, regardless of the confidence level that is chosen.

text: A comparison of methods for estimating prediction intervals in NIR spectroscopy: Size matters In this article we demonstrate that, when evaluating a method for determining prediction intervals, interval size matters more than coverage because the latter can be fixed at a chosen confidence level with good reliability. To achieve the desired coverage, we employ a simple non-parametric method to compute prediction intervals by calibrating estimated prediction errors, and we extend the basic method with a continuum correction to deal with small data sets. In our experiments on a collection of several NIR data sets, we evaluate several existing methods of computing prediction intervals for partial least-squares (PLS) regression. Our results show that, when coverage is fixed at a chosen confidence level, and the number of PLS components is selected to minimize squared error of point estimates, interval estimation based on the classic ordinary least-squares method produces the narrowest intervals, outperforming the U-deviation method and linearization, regardless of the confidence level that is chosen.

year: 2011

title: Restoring the flow: Challenging the existing management frameworks to integrate Mātauranga Māori

authors: Hall, Tredegar Rangiātea

subjects: tangata whenua water management

abstract: Within the context of the current regimes of fresh water management in Aotearoa, this thesis is an exploration of the significance of freshwater to Māori; our rangatiratanga, Treaty rights and ownership. The Māori world view and the way this relates to fresh water is described and contrasted with the principles and practices of water management in the contemporary neo-liberal governance structures of this country. The impacts of the commodification of water through ownership rights, the limited monitoring capacity and the inability to provide a governance structure that will work across diverse environments are seen to threaten the sustainability of a critical part of our environment. The primary focus of on this research is on the relationship between the exclusion of tangata whenua from decision making in resource management and the degradation of the environment.
 
The thesis comments on the development of resource management legislation and actions of the state in Aotearoa, and uses post-colonial theory as a starting point to document the subordinate relationship of Māori within contemporary governance. This has privileged mono-cultural and neoliberal forms of water management that has scarred Papatūānuku and threatens human sustainability into the future.
    
The recent co-management agreement for the Waikato River is the specific case study against which a recent effort to reduce the alienation of Māori is viewed. A kaupapa Māori methodology is used to acquire and understand the importance of mātauranga Māori/ Traditional Ecological Knowledge (TEK) and what is required for these principles to enhance water management practices within the case study area. The original contribution of the work is drawn from interviews conducted with Māori and others who are involved in or informed by the commitment to explore co-management sustainable management options. These views are woven into a substantial and interpretative commentary on the role of Māori in future water governance.

The thesis argues that the best way to enhance water management and environmental protection is by inducing a planning paradigm shift where tangata whenua are given greater influence in environmental decision making that resembles an equal Treaty of Waitangi partnership, where the ethic of kaitiakitanga is empowered. Such a strategy would allow decision making regarding water and environmental management to be more focused on what is best for the resource and its survival rather than what most cost effective for some owners of water rights. Encouraging the acceptance of mātauranga Māori and incorporating more efficient and sustainable innovative technologies can restore the mauri of water in our place.

text: Restoring the flow: Challenging the existing management frameworks to integrate Mātauranga Māori Within the context of the current regimes of fresh water management in Aotearoa, this thesis is an exploration of the significance of freshwater to Māori; our rangatiratanga, Treaty rights and ownership. The Māori world view and the way this relates to fresh water is described and contrasted with the principles and practices of water management in the contemporary neo-liberal governance structures of this country. The impacts of the commodification of water through ownership rights, the limited monitoring capacity and the inability to provide a governance structure that will work across diverse environments are seen to threaten the sustainability of a critical part of our environment. The primary focus of on this research is on the relationship between the exclusion of tangata whenua from decision making in resource management and the degradation of the environment.
 
The thesis comments on the development of resource management legislation and actions of the state in Aotearoa, and uses post-colonial theory as a starting point to document the subordinate relationship of Māori within contemporary governance. This has privileged mono-cultural and neoliberal forms of water management that has scarred Papatūānuku and threatens human sustainability into the future.
    
The recent co-management agreement for the Waikato River is the specific case study against which a recent effort to reduce the alienation of Māori is viewed. A kaupapa Māori methodology is used to acquire and understand the importance of mātauranga Māori/ Traditional Ecological Knowledge (TEK) and what is required for these principles to enhance water management practices within the case study area. The original contribution of the work is drawn from interviews conducted with Māori and others who are involved in or informed by the commitment to explore co-management sustainable management options. These views are woven into a substantial and interpretative commentary on the role of Māori in future water governance.

The thesis argues that the best way to enhance water management and environmental protection is by inducing a planning paradigm shift where tangata whenua are given greater influence in environmental decision making that resembles an equal Treaty of Waitangi partnership, where the ethic of kaitiakitanga is empowered. Such a strategy would allow decision making regarding water and environmental management to be more focused on what is best for the resource and its survival rather than what most cost effective for some owners of water rights. Encouraging the acceptance of mātauranga Māori and incorporating more efficient and sustainable innovative technologies can restore the mauri of water in our place.

year: 2012