title: Subsurface stratigraphy and petrology of a cool-water carbonate fracture reservoir - the mid-tertiary Tikorangi Formation, Taranaki Basin, New Zealand

authors: Hood, Steven D.

abstract: The totally subsurface Oligocene-Early Miocene Tikorangi Formation in Taranaki Basin is New Zealand’s only commercially-producing fractured-carbonate reservoir, but is poorly understood in a stratigraphic-sedimentological-diagenetic context. Based on correlation between laboratory and geophysical well log data a carbonate facies-based lithostratigraphy has been established for the first time for the entire formation. Petrogenesis of this complex siliciclastic-carbonate-dominated sequence, (re)deposited as a mix of retrogradational, progradational, and aggradational sedimentary sequences across a range of shallow-shelfal, foredeep and basinal settings, has been controlled by proximity to a rapidly evolving convergent Australian-Pacific plate boundary, to changes in relative sea level within an overall transgressive regime, to foredeep trough accommodation, to location within a cool-water temperate latitude setting, and to the changing availability and sources of carbonate and siliciclastic supply. 

The history and nature of burial diagenesis have been instrumental in the creation and subsequent modification of fracture porosity within the Tikorangi Formation by producing a tight, low porosity/permeability rock; burial replacive dolomitisation with no associated secondary porosity development; intense fracturing, thrusting, and folding in association with compression at the Australian-Pacific plate boundary; and precipitation of a complex suite of ferroan calcite, baroque dolomite, celestite, and quartzine minerals within fracture systems. Petrographic, trace element, stable isotope (δ¹⁸O and δ¹³C), and fluid inclusion data record a complex history of changing pore fluid chemistry and heating during burial, punctuated by relative changes in the input of downward circulating meteoric and upwelling basinal fluids. Precursory hydrocarbon-bearing fluids from Eocene terrestrial source rocks have migrated along with aqueous fluids after about 8 Ma, with major hydrocarbon emplacement within the fracture systems since the Early Pliocene. 

The Tikorangi Formation’s mixed siliciclastic-carbonate nature, heterozoan biotic carbonate make-up, low-Mg calcite mineralogy of skeletons and cements, and delayed deep burial diagenetic history are key features of current cool-water carbonate models. However, these evolving models of temperate carbonate sedimentation generally remain to incorporate several features exemplified by the Tikorangi Formation deposits, including: the recognition of a full spectrum of shelf-slope-basin facies and not simply shallow platform carbonates; the importance of mass emplacement events in producing complex mixed shelfal and deeper water skeletal assemblages; the textural diversity of deposits in which mudstones, wackestones and packstones are more common than grainstones; the ubiquitous occurrence of late diagenetic dolomite in the deposits; and the fact that cool-water carbonate facies can form economically important fracture reservoir rocks. While this study has provided new insights into the subsurface stratigraphy, petrology and diagenesis of the cool-water Tikorangi Formation carbonate fracture reservoir, an important research focus for the future is to further our understanding of temperate carbonate-dominated depositional and diagenetic systems as a whole, thereby enabling more concise assessment of their potential economic significance.

text: Subsurface stratigraphy and petrology of a cool-water carbonate fracture reservoir - the mid-tertiary Tikorangi Formation, Taranaki Basin, New Zealand The totally subsurface Oligocene-Early Miocene Tikorangi Formation in Taranaki Basin is New Zealand’s only commercially-producing fractured-carbonate reservoir, but is poorly understood in a stratigraphic-sedimentological-diagenetic context. Based on correlation between laboratory and geophysical well log data a carbonate facies-based lithostratigraphy has been established for the first time for the entire formation. Petrogenesis of this complex siliciclastic-carbonate-dominated sequence, (re)deposited as a mix of retrogradational, progradational, and aggradational sedimentary sequences across a range of shallow-shelfal, foredeep and basinal settings, has been controlled by proximity to a rapidly evolving convergent Australian-Pacific plate boundary, to changes in relative sea level within an overall transgressive regime, to foredeep trough accommodation, to location within a cool-water temperate latitude setting, and to the changing availability and sources of carbonate and siliciclastic supply. 

The history and nature of burial diagenesis have been instrumental in the creation and subsequent modification of fracture porosity within the Tikorangi Formation by producing a tight, low porosity/permeability rock; burial replacive dolomitisation with no associated secondary porosity development; intense fracturing, thrusting, and folding in association with compression at the Australian-Pacific plate boundary; and precipitation of a complex suite of ferroan calcite, baroque dolomite, celestite, and quartzine minerals within fracture systems. Petrographic, trace element, stable isotope (δ¹⁸O and δ¹³C), and fluid inclusion data record a complex history of changing pore fluid chemistry and heating during burial, punctuated by relative changes in the input of downward circulating meteoric and upwelling basinal fluids. Precursory hydrocarbon-bearing fluids from Eocene terrestrial source rocks have migrated along with aqueous fluids after about 8 Ma, with major hydrocarbon emplacement within the fracture systems since the Early Pliocene. 

The Tikorangi Formation’s mixed siliciclastic-carbonate nature, heterozoan biotic carbonate make-up, low-Mg calcite mineralogy of skeletons and cements, and delayed deep burial diagenetic history are key features of current cool-water carbonate models. However, these evolving models of temperate carbonate sedimentation generally remain to incorporate several features exemplified by the Tikorangi Formation deposits, including: the recognition of a full spectrum of shelf-slope-basin facies and not simply shallow platform carbonates; the importance of mass emplacement events in producing complex mixed shelfal and deeper water skeletal assemblages; the textural diversity of deposits in which mudstones, wackestones and packstones are more common than grainstones; the ubiquitous occurrence of late diagenetic dolomite in the deposits; and the fact that cool-water carbonate facies can form economically important fracture reservoir rocks. While this study has provided new insights into the subsurface stratigraphy, petrology and diagenesis of the cool-water Tikorangi Formation carbonate fracture reservoir, an important research focus for the future is to further our understanding of temperate carbonate-dominated depositional and diagenetic systems as a whole, thereby enabling more concise assessment of their potential economic significance.

year: 2000

title: Exploiting web 2.0 forallknowledge-based information retrieval

authors: Milne, David N.

subjects: computer science

abstract: This paper describes ongoing research into obtaining and using knowledge bases to assist information retrieval. These structures are prohibitively expensive to obtain manually, yet automatic approaches have been researched for decades with limited success. This research investigates a potential shortcut: a way to provide knowledge bases automatically, without expecting computers to replace expert human indexers. Instead we aim to replace the professionals with thousands or even millions of amateurs: with the growing community of contributors who form the core of Web 2.0. Specifically we focus on Wikipedia, which represents a rich tapestry of topics and semantics and a huge investment of human effort and judgment. We show how this can be directly exploited to provide manually-defined yet inexpensive knowledge-bases that are specifically tailored to expose the topics, terminology and semantics of individual document collections. We are also concerned with how best to make these structures available to users, and aim to produce a complete knowledge-based retrieval system-both the knowledge base and the tools to apply it-that can be evaluated by how well it assists real users in performing realistic and practical information retrieval tasks. To this end we have developed Koru, a new search engine that offers concrete evidence of the effectiveness of our Web 2.0 based techniques for assisting information retrieval.

text: Exploiting web 2.0 forallknowledge-based information retrieval This paper describes ongoing research into obtaining and using knowledge bases to assist information retrieval. These structures are prohibitively expensive to obtain manually, yet automatic approaches have been researched for decades with limited success. This research investigates a potential shortcut: a way to provide knowledge bases automatically, without expecting computers to replace expert human indexers. Instead we aim to replace the professionals with thousands or even millions of amateurs: with the growing community of contributors who form the core of Web 2.0. Specifically we focus on Wikipedia, which represents a rich tapestry of topics and semantics and a huge investment of human effort and judgment. We show how this can be directly exploited to provide manually-defined yet inexpensive knowledge-bases that are specifically tailored to expose the topics, terminology and semantics of individual document collections. We are also concerned with how best to make these structures available to users, and aim to produce a complete knowledge-based retrieval system-both the knowledge base and the tools to apply it-that can be evaluated by how well it assists real users in performing realistic and practical information retrieval tasks. To this end we have developed Koru, a new search engine that offers concrete evidence of the effectiveness of our Web 2.0 based techniques for assisting information retrieval.

year: 2007

title: Problematic reasoning under the guise of anti-Māori talk: A case study of the Three Waters tweets

authors: Tan, Kyle K. H.

abstract: Drawing from a subset of Twitter/X quotes (or tweets) on the politically controversial Three Waters Reform, this study identified forms of anti-Māori discourse through a deductive analysis. A complementary analysis was conducted to unpack how problematic reasoning fueled racism against Māori. Our results revealed distinct and interconnected themes—“resources,” “culture,” “stirrer,” “privilege,” and “one people”—that portrayed Māori as undeserving, lacking expertise, threatening, and unworthy of equitable treatment, as New Zealand citizens are entitled to enjoy liberal democratic values. Anti-Māori speakers employed problematic reasoning tactics to obstruct the public from understanding the truth or to encourage others to form ill-informed opinions through emotions, supposed authority, and conspiracy. Exemplar tweets were provided to illustrate the myriad instances of false information related to patterns of anti-Māori discourse. Evidence from this study makes the case for addressing racism on social media and creating interventions to expand media literacy amongst the public to discern problematic reasonings.

text: Problematic reasoning under the guise of anti-Māori talk: A case study of the Three Waters tweets Drawing from a subset of Twitter/X quotes (or tweets) on the politically controversial Three Waters Reform, this study identified forms of anti-Māori discourse through a deductive analysis. A complementary analysis was conducted to unpack how problematic reasoning fueled racism against Māori. Our results revealed distinct and interconnected themes—“resources,” “culture,” “stirrer,” “privilege,” and “one people”—that portrayed Māori as undeserving, lacking expertise, threatening, and unworthy of equitable treatment, as New Zealand citizens are entitled to enjoy liberal democratic values. Anti-Māori speakers employed problematic reasoning tactics to obstruct the public from understanding the truth or to encourage others to form ill-informed opinions through emotions, supposed authority, and conspiracy. Exemplar tweets were provided to illustrate the myriad instances of false information related to patterns of anti-Māori discourse. Evidence from this study makes the case for addressing racism on social media and creating interventions to expand media literacy amongst the public to discern problematic reasonings.

year: 2025