title: Dating Thach Lac: Cryptic CaCO₃ diagenesis in archaeological food shells and implications for ¹⁴c

authors: Petchey, Fiona

abstract: In many locations around the world, shell radiocarbon dates underpin archaeological research. The dating of shell brings the chronological relationship between the sample and target event (e.g., hunting and food preparation) into congruence, while shells are valuable geochemical proxies for understanding past climate dynamics and environments. However, this information can be lost as the shell, composites of biopolymers and carbonate minerals (mostly calcite and or aragonite), undergo diagenetic alteration. While studies into Pleistocene-age carbonates are common in the radiocarbon literature, there has been little research into the impact of alteration on Holocene-age shells used to interpret recent societal developments. The limits of our understanding of these diagenetic changes became evident when dating Placuna placenta (naturally calcitic) and Tegillarca granosa (naturally aragonitic) shells from the site of Thach Lac in Vietnam. These shells returned ages significantly younger than associated charcoal and terrestrial bone at the site, but standard tests for secondary recrystallization (XRD and staining techniques) did not indicate any alteration. Further investigation revealed that cryptic recrystallization (i.e., of the same crystal structure) had occurred in both the calcite and aragonite shells. This finding suggests recrystallization may have an undetected impact on some shell radiocarbon dates.

text: Dating Thach Lac: Cryptic CaCO₃ diagenesis in archaeological food shells and implications for ¹⁴c In many locations around the world, shell radiocarbon dates underpin archaeological research. The dating of shell brings the chronological relationship between the sample and target event (e.g., hunting and food preparation) into congruence, while shells are valuable geochemical proxies for understanding past climate dynamics and environments. However, this information can be lost as the shell, composites of biopolymers and carbonate minerals (mostly calcite and or aragonite), undergo diagenetic alteration. While studies into Pleistocene-age carbonates are common in the radiocarbon literature, there has been little research into the impact of alteration on Holocene-age shells used to interpret recent societal developments. The limits of our understanding of these diagenetic changes became evident when dating Placuna placenta (naturally calcitic) and Tegillarca granosa (naturally aragonitic) shells from the site of Thach Lac in Vietnam. These shells returned ages significantly younger than associated charcoal and terrestrial bone at the site, but standard tests for secondary recrystallization (XRD and staining techniques) did not indicate any alteration. Further investigation revealed that cryptic recrystallization (i.e., of the same crystal structure) had occurred in both the calcite and aragonite shells. This finding suggests recrystallization may have an undetected impact on some shell radiocarbon dates.

year: 2022

title: Navigating protection and presence: Trade-offs around data suppression for small Pacific populations

authors: Turner, Helen

subjects: data suppression

abstract: Introduction: Datasets, their analytics and their interpretation are key decision support tools for Pacific Island communities, with the potential to shape public policy, healthcare, and social interventions in the Pacific ‘Blue Continent’. However, in the case of numerically small island populations, privacy concerns have motivated widespread use of data suppression. While suppression safeguards privacy, it also risks erasing the visibility of these populations, leading to ‘statistical invisibility’ that obscures the social, health, and economic challenges. This study critically reviews the practice of data suppression, emphasizing its rationale in privacy protection, but also highlighting the impacts on resource allocation, advocacy, and equitable policy-making for Pacific populations.


Methods: We explored the rationale behind data suppression, and its legal and regulatory context. Using case studies including the U.S. Census Bureau, Centers for Disease Control and Behavioral Risk Factor Surveillance System, we assess the impact of suppression thresholds and privacy-preserving methods on Pacific Island communities. We present a novel analysis of data suppression impacts on ICD code suppression across different levels of geographical units in the Pacific to illustrate disproportionate impacts. We review alternative privacy-preserving methods, including data smoothing, statistical masking, and synthetic data generation, that could mitigate the effects of suppression without compromising individual privacy.


Finding and Conclusions: We recommend inclusive and transparent data practices needed to prevent data suppression compounding systemic marginalization of small Pacific populations. By critically evaluating current practices and proposing alternative strategies grounded in ‘Critical Data Theory’ and Pacific knowledge epistemology, this paper aims to inform policies that balance protection of individual privacy with the accurate representation of small, geographically dispersed populations.

text: Navigating protection and presence: Trade-offs around data suppression for small Pacific populations Introduction: Datasets, their analytics and their interpretation are key decision support tools for Pacific Island communities, with the potential to shape public policy, healthcare, and social interventions in the Pacific ‘Blue Continent’. However, in the case of numerically small island populations, privacy concerns have motivated widespread use of data suppression. While suppression safeguards privacy, it also risks erasing the visibility of these populations, leading to ‘statistical invisibility’ that obscures the social, health, and economic challenges. This study critically reviews the practice of data suppression, emphasizing its rationale in privacy protection, but also highlighting the impacts on resource allocation, advocacy, and equitable policy-making for Pacific populations.


Methods: We explored the rationale behind data suppression, and its legal and regulatory context. Using case studies including the U.S. Census Bureau, Centers for Disease Control and Behavioral Risk Factor Surveillance System, we assess the impact of suppression thresholds and privacy-preserving methods on Pacific Island communities. We present a novel analysis of data suppression impacts on ICD code suppression across different levels of geographical units in the Pacific to illustrate disproportionate impacts. We review alternative privacy-preserving methods, including data smoothing, statistical masking, and synthetic data generation, that could mitigate the effects of suppression without compromising individual privacy.


Finding and Conclusions: We recommend inclusive and transparent data practices needed to prevent data suppression compounding systemic marginalization of small Pacific populations. By critically evaluating current practices and proposing alternative strategies grounded in ‘Critical Data Theory’ and Pacific knowledge epistemology, this paper aims to inform policies that balance protection of individual privacy with the accurate representation of small, geographically dispersed populations.

year: 2025

title: Participatory design in Māori cultural contexts

authors: Bowen, Judy

subjects: computer science

abstract: The Hakituri project aims to develop practical and ethical wearable monitoring solutions for workers in hazardous industries. We identified specific challenges pertinent to our participatory design process for this project which relate to the indigenous participants, cultural expectations and data sovereignty. As we developed the ideas for our design process, further challenges became evident. In this paper we explore the challenges that unfolded and describe how we began to mitigate them and develop ideas for similar future challenges.

text: Participatory design in Māori cultural contexts The Hakituri project aims to develop practical and ethical wearable monitoring solutions for workers in hazardous industries. We identified specific challenges pertinent to our participatory design process for this project which relate to the indigenous participants, cultural expectations and data sovereignty. As we developed the ideas for our design process, further challenges became evident. In this paper we explore the challenges that unfolded and describe how we began to mitigate them and develop ideas for similar future challenges.

year: 2020