title: Non-orthogonally transitive G₂ spike solution

authors: Lim, Woei Chet

subjects: Science & Technology

abstract: We generalize the orthogonally transitive (OT) G₂ spike solution to the non-OT G₂ case. This is achieved by applying Geroch's transformation on a Kasner seed. The new solution contains two more parameters than the OT G₂ spike solution. Unlike the OT G₂ spike solution, the new solution always resolves its spike.

text: Non-orthogonally transitive G₂ spike solution We generalize the orthogonally transitive (OT) G₂ spike solution to the non-OT G₂ case. This is achieved by applying Geroch's transformation on a Kasner seed. The new solution contains two more parameters than the OT G₂ spike solution. Unlike the OT G₂ spike solution, the new solution always resolves its spike.

year: 2015

title: Late Holocene mud sedimentation and diagenesis in the Firth of Thames: Bentonites in the making

authors: Naish, Timothy R.

abstract: Late Holocene mud sedimentation in the southern Firth of Thames has been described from analysis of a number of shallow marine sediment cores. Three distinct lithofacies are distinguished on the basis of sediment texture and mineralogy. A laterally extensive greenish grey mud, typically bioturbated and massive, with sporadic uncorrelatable interbedded shell layers is termed the Firth of Thames mud facies. Nearer shore sediments are usually coarser and are subdivided into two facies: a siliciclastic sand facies (river mouth sand facies) comprising more prominent interbeds of sand in mud and associated with sedimentation at the mouth of the Waihou River; and a mixed terrigenous-carbonate gravel facies (delta fan gravel facies) associated with deposition on small delta fans adjacent to streams draining the Coromandel Range. The areal distribution of all three facies over the late Holocene has been controlled largely by northward progradation of the coastal Hauraki Lowland associated with the rapid sediment infilling of the Firth of Thames since sea level reached its present height 6500 y B.P. From seismic evidence the Holocene muds are up to 10m thick. The cores in this study penetrated only to 5.5m sub-bottom depth and yielded an oldest radiocarbon age of 5000 y B.P. The age data indicate an average rate of offshore vertical sediment accumulation of 1.5 mm/y. 

Up to 15 km of progradation of the southern shoreline of the coastal Hauraki Lowland has occurred over the late Holocene at an average rate of up to 2.5 m/y, notably from 3500 y B.P to 1200 y B.P. Progradation is evidenced by the occurrence of coarsening-upward sequences in nearer shore cores of the Firth of Thames, as well as their changing faunal composition, particularly the upward increase in abundance of the foraminifer Ammonia beccarri, a good indicator of brackish water conditions, which suggests a gradual seaward encroachment of the freshwater influence of the Waihou River over the late Holocene. Basal muds which are similar in composition to marine sediments of the Firth of Thames are overlain by peat dated at 6025 y B.P in a peat core from Kopouatai Peat Bog, and suggest that marine conditions existed in this inland region of the Hauraki Depression prior to 6025 y B.P. 

Muds range from silty clays to clayey silts and consist principally of volcanic glass, smectite and halloysite, with smaller amounts of other volcanic-derived siliciclasts and allophane and illite, as well as skeletal carbonate (mainly aragonite) and organic matter. A contemporaneous decrease in the abundance of volcanic glass (55-15 wt % down-core) and an increase in smectite concentration (8-45 wt % down-core) occurs with sub-bottom depth. Specific mineralogical analyses (XRD and IR) and evidence from scanning electron microscopy suggest the smectite is montmorillonitic in composition and authigenic in nature. Moreover, the absence of smectite in the bottom sediments of rivers draining the Hauraki Lowland precludes a detrital origin.

The diagenetic transformation of volcanic glass to smectite in sediments of the Firth of Thames is described by a sequential kinetic model which involves a parabolic dissolution coupled with a first order precipitation of smectite via the formation of an intermediate hydrated glass phase. The rate constant calculated from the sequential kinetic model is 3.35 x 10⁻⁴y⁻¹. The half-life of the glass is 1475 y, implying rapid early diagenetic alteration of volcanic glass to smectite to form late Holocene bentonitic deposits. Thermodynamic stability considerations imply that the first order precipitaion of smectite may be favoured by conditions of pH and Na⁺ activity typical of interstitial fluids having sea water salinity under mildly anoxic conditions.

text: Late Holocene mud sedimentation and diagenesis in the Firth of Thames: Bentonites in the making Late Holocene mud sedimentation in the southern Firth of Thames has been described from analysis of a number of shallow marine sediment cores. Three distinct lithofacies are distinguished on the basis of sediment texture and mineralogy. A laterally extensive greenish grey mud, typically bioturbated and massive, with sporadic uncorrelatable interbedded shell layers is termed the Firth of Thames mud facies. Nearer shore sediments are usually coarser and are subdivided into two facies: a siliciclastic sand facies (river mouth sand facies) comprising more prominent interbeds of sand in mud and associated with sedimentation at the mouth of the Waihou River; and a mixed terrigenous-carbonate gravel facies (delta fan gravel facies) associated with deposition on small delta fans adjacent to streams draining the Coromandel Range. The areal distribution of all three facies over the late Holocene has been controlled largely by northward progradation of the coastal Hauraki Lowland associated with the rapid sediment infilling of the Firth of Thames since sea level reached its present height 6500 y B.P. From seismic evidence the Holocene muds are up to 10m thick. The cores in this study penetrated only to 5.5m sub-bottom depth and yielded an oldest radiocarbon age of 5000 y B.P. The age data indicate an average rate of offshore vertical sediment accumulation of 1.5 mm/y. 

Up to 15 km of progradation of the southern shoreline of the coastal Hauraki Lowland has occurred over the late Holocene at an average rate of up to 2.5 m/y, notably from 3500 y B.P to 1200 y B.P. Progradation is evidenced by the occurrence of coarsening-upward sequences in nearer shore cores of the Firth of Thames, as well as their changing faunal composition, particularly the upward increase in abundance of the foraminifer Ammonia beccarri, a good indicator of brackish water conditions, which suggests a gradual seaward encroachment of the freshwater influence of the Waihou River over the late Holocene. Basal muds which are similar in composition to marine sediments of the Firth of Thames are overlain by peat dated at 6025 y B.P in a peat core from Kopouatai Peat Bog, and suggest that marine conditions existed in this inland region of the Hauraki Depression prior to 6025 y B.P. 

Muds range from silty clays to clayey silts and consist principally of volcanic glass, smectite and halloysite, with smaller amounts of other volcanic-derived siliciclasts and allophane and illite, as well as skeletal carbonate (mainly aragonite) and organic matter. A contemporaneous decrease in the abundance of volcanic glass (55-15 wt % down-core) and an increase in smectite concentration (8-45 wt % down-core) occurs with sub-bottom depth. Specific mineralogical analyses (XRD and IR) and evidence from scanning electron microscopy suggest the smectite is montmorillonitic in composition and authigenic in nature. Moreover, the absence of smectite in the bottom sediments of rivers draining the Hauraki Lowland precludes a detrital origin.

The diagenetic transformation of volcanic glass to smectite in sediments of the Firth of Thames is described by a sequential kinetic model which involves a parabolic dissolution coupled with a first order precipitation of smectite via the formation of an intermediate hydrated glass phase. The rate constant calculated from the sequential kinetic model is 3.35 x 10⁻⁴y⁻¹. The half-life of the glass is 1475 y, implying rapid early diagenetic alteration of volcanic glass to smectite to form late Holocene bentonitic deposits. Thermodynamic stability considerations imply that the first order precipitaion of smectite may be favoured by conditions of pH and Na⁺ activity typical of interstitial fluids having sea water salinity under mildly anoxic conditions.

year: 1990

title: Te ahunga atu ki ngā ōhanga oranga Māori: Towards Māori economies of wellbeing - Ngā whānau i te pokapū o te oranga

authors: Spiller, Chellie

abstract: Nau mai ki tēnei kohinga o ngā whakaaro me ngā tikanga e pā ana ki te oranga ohaoha Māori. Ko tō mātou kaupapa matua ko te whānau; e hiahia ana mātou ki te whakaatu i ngā huarahi ki te ora pai mō te whānau i roto i ngā horopaki ohaoha. Ko te ao Māori tō mātou tūāpapa. E whakakao ana tēnei pukapuka i te huhua o ngā reo me ngā tirohanga nō te ao Māori, me ētahi atu wheako e hāngai ana. Kua kotahi mātou ki raro i te taumarumaru o te kaupapa tūturu kotahi: arā, te oranga pai mō ngā whānau. Ko te tūmanako ka tautoko, ka whakaohooho anō hoki tēnei pukapuka i ngā tāngata kia hōhonu atu tā rātou hono ki tēnei kaupapa whaitake, kia whai māramatanga whaihua hoki rātou.

Welcome to this collection of thoughts and practices related to Māori economic life. Our primary focus is the whānau; we want to show ways to live well for the whānau in economic contexts. Our foundation is te ao Māori. This book brings together many voices and perspectives from the Māori world and other relevant experiences. We are united in one true purpose: the good livelihood of whānau. We hope this book will support and inspire people to connect more deeply with this critical topic and gain valuable insights.

text: Te ahunga atu ki ngā ōhanga oranga Māori: Towards Māori economies of wellbeing - Ngā whānau i te pokapū o te oranga Nau mai ki tēnei kohinga o ngā whakaaro me ngā tikanga e pā ana ki te oranga ohaoha Māori. Ko tō mātou kaupapa matua ko te whānau; e hiahia ana mātou ki te whakaatu i ngā huarahi ki te ora pai mō te whānau i roto i ngā horopaki ohaoha. Ko te ao Māori tō mātou tūāpapa. E whakakao ana tēnei pukapuka i te huhua o ngā reo me ngā tirohanga nō te ao Māori, me ētahi atu wheako e hāngai ana. Kua kotahi mātou ki raro i te taumarumaru o te kaupapa tūturu kotahi: arā, te oranga pai mō ngā whānau. Ko te tūmanako ka tautoko, ka whakaohooho anō hoki tēnei pukapuka i ngā tāngata kia hōhonu atu tā rātou hono ki tēnei kaupapa whaitake, kia whai māramatanga whaihua hoki rātou.

Welcome to this collection of thoughts and practices related to Māori economic life. Our primary focus is the whānau; we want to show ways to live well for the whānau in economic contexts. Our foundation is te ao Māori. This book brings together many voices and perspectives from the Māori world and other relevant experiences. We are united in one true purpose: the good livelihood of whānau. We hope this book will support and inspire people to connect more deeply with this critical topic and gain valuable insights.

year: 2025