title: Volcanology of the Raventhorpe and Pokeno West Volcanic Complexes, South Auckland Volcanic Field

authors: Taylor, Simon Nicholas

subjects: South Auckland Volcanic Field

abstract: The South Auckland volcanic field hosts at least 82 volcanic centres throughout the Pukekohe, Bombay, Tuakau, Pukekawa and Onewhero regions. The monogenetic basaltic volcanic field was active between 1.59 to 0.51 Ma, producing tuff rings, maar craters, scoria cones, and basaltic lava flows covering an area of 300 km2.

Two volcanic complexes have been studied in this thesis: the Raventhorpe volcanic complex, and the Pokeno West volcanic complex. The Raventhorpe complex hosts six interconnected and overlapping tuff rings (the Raventhorpe and five Ingram Road tuff rings) and the Rutherford Road scoria cone with several lava flows. The Pokeno West volcanic complex hosts a single tuff ring and surrounding lava flows. Each complex has been mapped and stratigraphic logs of exposed sections have been constructed. Measurements have been made of componentry (juveniles, lithics, crystals) and vesicularity of juvenile clasts. Petrography of the tuff rings, mineralogy (including selected electron microprobe analyses) and geochemistry by XRF has been undertaken to characterise the deposits. These data have been compiled and used for facies analysis, and to determine styles of eruption and their controlling factors.

The tuff ring facies of Raventhorpe include finely fragmented laminated to thinly bedded surge beds, coarse planar fall beds, and a massive magmatic block and bomb bed. The data show evidence for eruption drying out in the early stages moving to a Strombolian phase before reverting back to a phreatomagmatic style. Petrographic data indicates the Kaawa Formation aquifers were very important in the eruption dynamics, with the localisation of vents controlled by the St. Stevens Fault.
The facies of the Pokeno West tuff ring include finely fragmented laminated or thinly bedded surge beds, cross bedded surge beds, planar bedded fall beds, and massive magmatic coarse lapilli beds. The data suggest variable eruption styles occurred alternating between phreatomagmatic and Strombolian. Petrographic analysis of lithic clasts indicates the Kaawa Formation aquifers were important in the eruption dynamics and the localisation of the tuff ring could be related to the Waikato or Pukekawa faults. The presence of the Kidnappers Ignimbrite allows for a new age constraint based on stratigraphy (>1.0 Ma).

GIS analysis of the South Auckland volcanic field indicates fault location is the main control on the distribution of volcanic centres. The type of volcanism occurring is related to the hydrogeological parameters of underlying strata, which throughout the Manukau Lowlands is the Kaawa Formation. However, there are several dry magmatic volcanic centres in the Manukau Lowlands which could indicate another control by rate of magma flux which if rapid enough could prevent water-magma interaction. The distribution of age constrained centres has been statistically verified to be random.

text: Volcanology of the Raventhorpe and Pokeno West Volcanic Complexes, South Auckland Volcanic Field The South Auckland volcanic field hosts at least 82 volcanic centres throughout the Pukekohe, Bombay, Tuakau, Pukekawa and Onewhero regions. The monogenetic basaltic volcanic field was active between 1.59 to 0.51 Ma, producing tuff rings, maar craters, scoria cones, and basaltic lava flows covering an area of 300 km2.

Two volcanic complexes have been studied in this thesis: the Raventhorpe volcanic complex, and the Pokeno West volcanic complex. The Raventhorpe complex hosts six interconnected and overlapping tuff rings (the Raventhorpe and five Ingram Road tuff rings) and the Rutherford Road scoria cone with several lava flows. The Pokeno West volcanic complex hosts a single tuff ring and surrounding lava flows. Each complex has been mapped and stratigraphic logs of exposed sections have been constructed. Measurements have been made of componentry (juveniles, lithics, crystals) and vesicularity of juvenile clasts. Petrography of the tuff rings, mineralogy (including selected electron microprobe analyses) and geochemistry by XRF has been undertaken to characterise the deposits. These data have been compiled and used for facies analysis, and to determine styles of eruption and their controlling factors.

The tuff ring facies of Raventhorpe include finely fragmented laminated to thinly bedded surge beds, coarse planar fall beds, and a massive magmatic block and bomb bed. The data show evidence for eruption drying out in the early stages moving to a Strombolian phase before reverting back to a phreatomagmatic style. Petrographic data indicates the Kaawa Formation aquifers were very important in the eruption dynamics, with the localisation of vents controlled by the St. Stevens Fault.
The facies of the Pokeno West tuff ring include finely fragmented laminated or thinly bedded surge beds, cross bedded surge beds, planar bedded fall beds, and massive magmatic coarse lapilli beds. The data suggest variable eruption styles occurred alternating between phreatomagmatic and Strombolian. Petrographic analysis of lithic clasts indicates the Kaawa Formation aquifers were important in the eruption dynamics and the localisation of the tuff ring could be related to the Waikato or Pukekawa faults. The presence of the Kidnappers Ignimbrite allows for a new age constraint based on stratigraphy (>1.0 Ma).

GIS analysis of the South Auckland volcanic field indicates fault location is the main control on the distribution of volcanic centres. The type of volcanism occurring is related to the hydrogeological parameters of underlying strata, which throughout the Manukau Lowlands is the Kaawa Formation. However, there are several dry magmatic volcanic centres in the Manukau Lowlands which could indicate another control by rate of magma flux which if rapid enough could prevent water-magma interaction. The distribution of age constrained centres has been statistically verified to be random.

year: 2012

title: Threshold cointegration and the short-run dynamics of twin deficit behaviour

authors: Holmes, Mark J.

subjects: current account balance

abstract: This paper examines the relationship between the current account and budget balances by means of a threshold cointegration approach advocated by Hansen and Seo (2002). Using US data covering 1947–2009, a long-run positive cointegrating relationship is confirmed. This supports the notion of a Keynesian twin deficits relationship. The short-run dynamics are investigated through an estimated threshold vector error correction model. Depending on the regime present, it is either the external or internal balance that is responsible for error correction. This has important implications for the use of fiscal policy to control the external balance.

text: Threshold cointegration and the short-run dynamics of twin deficit behaviour This paper examines the relationship between the current account and budget balances by means of a threshold cointegration approach advocated by Hansen and Seo (2002). Using US data covering 1947–2009, a long-run positive cointegrating relationship is confirmed. This supports the notion of a Keynesian twin deficits relationship. The short-run dynamics are investigated through an estimated threshold vector error correction model. Depending on the regime present, it is either the external or internal balance that is responsible for error correction. This has important implications for the use of fiscal policy to control the external balance.

year: 2010

title: Who owns native nature? Discourses of rights to land, culture, and knowledge in New Zealand

authors: Goldsmith, Michael

subjects: indigenous cultures

abstract: Michael Brown famously asked ‘Who owns native culture?’ This paper revisits that question by analyzing what happens to culture when the culturally defined boundary between it and nature becomes salient in the context of disputes between indigenous and settler populations. My case study is the dispute between the New Zealand government and Maori tribal groupings concerning ownership of the foreshore and seabed. Having been granted the right to test their claims in court in 2003, Maori groups were enraged when the government legislated the right out of existence in 2004. Though the reasons for doing so were clearly political, contrasting cultural assumptions appeared to set Maori and Pakeha (New Zealanders of European origin) at odds. While couching ownership of part of nature as an IPR issue may seem counter-intuitive, I argue that as soon as a property claim destabilizes the nature/culture boundary, IPR discourse becomes pertinent.

text: Who owns native nature? Discourses of rights to land, culture, and knowledge in New Zealand Michael Brown famously asked ‘Who owns native culture?’ This paper revisits that question by analyzing what happens to culture when the culturally defined boundary between it and nature becomes salient in the context of disputes between indigenous and settler populations. My case study is the dispute between the New Zealand government and Maori tribal groupings concerning ownership of the foreshore and seabed. Having been granted the right to test their claims in court in 2003, Maori groups were enraged when the government legislated the right out of existence in 2004. Though the reasons for doing so were clearly political, contrasting cultural assumptions appeared to set Maori and Pakeha (New Zealanders of European origin) at odds. While couching ownership of part of nature as an IPR issue may seem counter-intuitive, I argue that as soon as a property claim destabilizes the nature/culture boundary, IPR discourse becomes pertinent.

year: 2009