title: Emplacement processes of ignimbrites in the Ongatiti Valley, southeast Te Kuiti

authors: Brink, Megan Tracy

abstract: The Mangakino volcanic centre (MVC) is the oldest rhyolitic volcano of the Taupo Volcanic Zone (TVZ) located on the westernmost boundary. Ten eruptive deposits have been derived from the MVC and this study focuses on the 1.21 ± 0.04 Ma Ongatiti Ignimbrite and the 1.20 ± 0.04 Ma Unit D fall and overlying ignimbrite deposit. The Taupo volcanic centre (TVC), located at the southern boundary of the central TVZ is currently active and is considered to be the most active and productive rhyolitic centre on Earth. There have been multiple eruptions derived from the TVC over the past 350 – 320 ka, however the most recent Taupo eruption dated at 232 AD is the only deposit studied in this research. The study area is situated within the Ongatiti Valley, 15 km SE of Te Kuiti. It is 28 km west of the Mangakino caldera rim, and is located to the west of the upstanding Mesozoic basement block of the Rangitoto Range. 

A 1:25 000 geological map of the volcanic geology exposed within the Ongatiti Valley is produced. Detailed stratigraphc logs, petrographic descriptions and quantitative analysis on the mineralogy are given for all of the exposed eruptive deposits. The geochemical composition of the Ongatiti Ignimbrite and Unit D are determined through XRF, Electron microprobe and ICPMS analyses. 

Stratigraphic sections of the Ongatiti Ignimbrite in well exposed 25 m high outcrops in the Ongatiti Valley show variations in pumice, crystal, and lithic abundance, both vertically and laterally. Two units can be distinguished within the Ongatiti Ignimbrite overlying a poorly exposed lowermost fall deposit: a lower densely to partially welded, crystal-rich, pumice-poor flow sequence, and an upper densely to partially welded pumice and crystal-rich flow sequence. The boundary between the two units is wavy and gradational, and varies in altitude over relatively short distances. This undulating boundary is considered to result from interaction of pyroclastic density currents flowing both over and around the high-standing Rangitoto Range, and then covering a highly irregular pre-ignimbrite topography in the King Country. 

In the Ongatiti Valley, Unit D consists of several phreatoplinian fall deposits, a fine-grained ignimbrite and an overlying coarser-grained ignimbrite with a combined thickness of 3 m. A stratigraphic log is presented and the characteristic textures, structure, petrography and geochemistry is described. A six stage process is suggested for the change in the conditions/styles and intensities between the different phases of the eruption. 

A 15 m high valley-ponded section of the 232 AD Taupo Ignimbrite occurs in the Waipa River Valley, that contains fossilised tree trunks in position of growth. A possible origin involving variation in dynamic pressure and subsequent destructive power of pyroclastic density currents is developed.

text: Emplacement processes of ignimbrites in the Ongatiti Valley, southeast Te Kuiti The Mangakino volcanic centre (MVC) is the oldest rhyolitic volcano of the Taupo Volcanic Zone (TVZ) located on the westernmost boundary. Ten eruptive deposits have been derived from the MVC and this study focuses on the 1.21 ± 0.04 Ma Ongatiti Ignimbrite and the 1.20 ± 0.04 Ma Unit D fall and overlying ignimbrite deposit. The Taupo volcanic centre (TVC), located at the southern boundary of the central TVZ is currently active and is considered to be the most active and productive rhyolitic centre on Earth. There have been multiple eruptions derived from the TVC over the past 350 – 320 ka, however the most recent Taupo eruption dated at 232 AD is the only deposit studied in this research. The study area is situated within the Ongatiti Valley, 15 km SE of Te Kuiti. It is 28 km west of the Mangakino caldera rim, and is located to the west of the upstanding Mesozoic basement block of the Rangitoto Range. 

A 1:25 000 geological map of the volcanic geology exposed within the Ongatiti Valley is produced. Detailed stratigraphc logs, petrographic descriptions and quantitative analysis on the mineralogy are given for all of the exposed eruptive deposits. The geochemical composition of the Ongatiti Ignimbrite and Unit D are determined through XRF, Electron microprobe and ICPMS analyses. 

Stratigraphic sections of the Ongatiti Ignimbrite in well exposed 25 m high outcrops in the Ongatiti Valley show variations in pumice, crystal, and lithic abundance, both vertically and laterally. Two units can be distinguished within the Ongatiti Ignimbrite overlying a poorly exposed lowermost fall deposit: a lower densely to partially welded, crystal-rich, pumice-poor flow sequence, and an upper densely to partially welded pumice and crystal-rich flow sequence. The boundary between the two units is wavy and gradational, and varies in altitude over relatively short distances. This undulating boundary is considered to result from interaction of pyroclastic density currents flowing both over and around the high-standing Rangitoto Range, and then covering a highly irregular pre-ignimbrite topography in the King Country. 

In the Ongatiti Valley, Unit D consists of several phreatoplinian fall deposits, a fine-grained ignimbrite and an overlying coarser-grained ignimbrite with a combined thickness of 3 m. A stratigraphic log is presented and the characteristic textures, structure, petrography and geochemistry is described. A six stage process is suggested for the change in the conditions/styles and intensities between the different phases of the eruption. 

A 15 m high valley-ponded section of the 232 AD Taupo Ignimbrite occurs in the Waipa River Valley, that contains fossilised tree trunks in position of growth. A possible origin involving variation in dynamic pressure and subsequent destructive power of pyroclastic density currents is developed.

year: 2012

title: Generating power: gender, ethnicity and empowerment in India's Narmada Valley

authors: Kurian, Priya A.

subjects: gender

abstract: Current analyses of issues relating to ethnicity and empowerment are silent about the significance of the environment in shaping and being shaped by human relations. For its part, environmental policy research, with few exceptions, has also ignored the dynamics of identity construction and cultural values that inform human relationships with the environment and thus affect environmental sustainability. I address this gap in the scholarship through an analysis of the Sardar Sarovar Project [SSP] in India. I explore the interweaving of the constructions of gender, ethnicity and empowerment and their implications for a new politics of the environment - the politics of environmental justice. I argue that discourses of modernization underpin the arguments of all those who discuss the SSP, whether in favour or against.

text: Generating power: gender, ethnicity and empowerment in India's Narmada Valley Current analyses of issues relating to ethnicity and empowerment are silent about the significance of the environment in shaping and being shaped by human relations. For its part, environmental policy research, with few exceptions, has also ignored the dynamics of identity construction and cultural values that inform human relationships with the environment and thus affect environmental sustainability. I address this gap in the scholarship through an analysis of the Sardar Sarovar Project [SSP] in India. I explore the interweaving of the constructions of gender, ethnicity and empowerment and their implications for a new politics of the environment - the politics of environmental justice. I argue that discourses of modernization underpin the arguments of all those who discuss the SSP, whether in favour or against.

year: 2000

title: Putting Sylvia in her place: Ashton-Warner as New Zealand educational theorist

authors: Middleton, Sue

subjects: Sylvia Ashton-Warner

abstract: Sylvia Ashton-Warner, a New Zealand teacher, won international acclaim in the 1950s-1950s with her novels, autobiographies, and accounts of her educational theory. Blurring genres between fiction and autobiography, much of her writing was centred on the ‘creative teaching scheme’ she developed in Maori Schools. At the heart of the scheme was the idea that literacy was best achieved when children captioned their experiences of fear and sex, the two great (Freudian) drives. In Sylvia’s infant room, these erupted to the surface by means of captions (a child’s ‘key vocabulary’). I introduce Lefebvre’s idea of ‘rhythm analysis’, applying it first to the teaching scheme, then to the ‘system’ in which Ashton-Warner taught. With reference to extracts from Ashton-Warner’s Creative Teaching Scheme and Myself, I connect the rhythms of her life with her ‘theory.’ I identify Sylvia’s own ‘key words’ (violence and war; ghosts; sex and the kiss) and their rhythmic engagements and collisions with educational ‘authorities.’

text: Putting Sylvia in her place: Ashton-Warner as New Zealand educational theorist Sylvia Ashton-Warner, a New Zealand teacher, won international acclaim in the 1950s-1950s with her novels, autobiographies, and accounts of her educational theory. Blurring genres between fiction and autobiography, much of her writing was centred on the ‘creative teaching scheme’ she developed in Maori Schools. At the heart of the scheme was the idea that literacy was best achieved when children captioned their experiences of fear and sex, the two great (Freudian) drives. In Sylvia’s infant room, these erupted to the surface by means of captions (a child’s ‘key vocabulary’). I introduce Lefebvre’s idea of ‘rhythm analysis’, applying it first to the teaching scheme, then to the ‘system’ in which Ashton-Warner taught. With reference to extracts from Ashton-Warner’s Creative Teaching Scheme and Myself, I connect the rhythms of her life with her ‘theory.’ I identify Sylvia’s own ‘key words’ (violence and war; ghosts; sex and the kiss) and their rhythmic engagements and collisions with educational ‘authorities.’

year: 2009