title: Provenance history of a Late Triassic-Jurassic Gondwana margin forearc basin, Murihiku Terrane, North Island, New Zealand: petrographic and geochemical constraints

authors: Briggs, Roger M.

subjects: Murihiku Terrane

abstract: The Murihiku Terrane in the North Island was a forearc basin adjacent to a volcanic arc along the eastern margin of Gondwana during the Mesozoic. The rocks that infill the basin are mainly volcaniclastic sandstones and mudstones, often turbiditic, with sparse shellbeds, rhyolitic tuffs, carbonaceous sandstones, plant beds, concretionary horizons, and rare thick granitoid-rich conglomerates. Petrographic studies of the rock fragments in the sandstones show that andesites are the dominant lithic type, but there is a wide range of other lithologies, including dacites, rhyolites, ignimbrites, granitoids, quartzofeldspathic mica schists, rare amphibolites, and reworked mudstones and sandstones. The sandstones are texturally and mineralogically immature and suggest deposition relatively close to a source of high relief, undergoing physical rather than chemical weathering in cool- to cold-temperate conditions. Geochemical analyses of 67 whole-rock volcaniclastic sandstones and siltstones indicate that they were derived from an active and dissected volcanic arc in a convergent margin setting built upon relatively thin continental crust. Modal petrographic data and whole-rock geochemistry both confirm that there were systematic variations with time in the composition of clastic material being supplied to the basin. From the Late Triassic to Middle Jurassic, there was a decrease in silicic volcanic material, plutonics, and metamorphics, and an increase in the supply of andesitic detritus. This was followed in the Late Jurassic by a broader range of volcanic detritus, varying from basaltic andesite to rhyolite, which may have been caused by progressive extension of the volcanic arc and thinning of the crust, a precursor to the breakup of Gondwana in the Early-Middle Cretaceous. Comparison with the Southland segment of the Murihiku Terrane in the South Island suggests that there were significant along-arc source variations, with relatively less silicic but greater andesitic and continental crust contributions in the North Island than in Southland. This may be analogous to the modern Taupo-Kermadec arc where there is a south-north along-arc transition from a continental to an oceanic arc.

text: Provenance history of a Late Triassic-Jurassic Gondwana margin forearc basin, Murihiku Terrane, North Island, New Zealand: petrographic and geochemical constraints The Murihiku Terrane in the North Island was a forearc basin adjacent to a volcanic arc along the eastern margin of Gondwana during the Mesozoic. The rocks that infill the basin are mainly volcaniclastic sandstones and mudstones, often turbiditic, with sparse shellbeds, rhyolitic tuffs, carbonaceous sandstones, plant beds, concretionary horizons, and rare thick granitoid-rich conglomerates. Petrographic studies of the rock fragments in the sandstones show that andesites are the dominant lithic type, but there is a wide range of other lithologies, including dacites, rhyolites, ignimbrites, granitoids, quartzofeldspathic mica schists, rare amphibolites, and reworked mudstones and sandstones. The sandstones are texturally and mineralogically immature and suggest deposition relatively close to a source of high relief, undergoing physical rather than chemical weathering in cool- to cold-temperate conditions. Geochemical analyses of 67 whole-rock volcaniclastic sandstones and siltstones indicate that they were derived from an active and dissected volcanic arc in a convergent margin setting built upon relatively thin continental crust. Modal petrographic data and whole-rock geochemistry both confirm that there were systematic variations with time in the composition of clastic material being supplied to the basin. From the Late Triassic to Middle Jurassic, there was a decrease in silicic volcanic material, plutonics, and metamorphics, and an increase in the supply of andesitic detritus. This was followed in the Late Jurassic by a broader range of volcanic detritus, varying from basaltic andesite to rhyolite, which may have been caused by progressive extension of the volcanic arc and thinning of the crust, a precursor to the breakup of Gondwana in the Early-Middle Cretaceous. Comparison with the Southland segment of the Murihiku Terrane in the South Island suggests that there were significant along-arc source variations, with relatively less silicic but greater andesitic and continental crust contributions in the North Island than in Southland. This may be analogous to the modern Taupo-Kermadec arc where there is a south-north along-arc transition from a continental to an oceanic arc.

year: 2004-12-01

title: Application of lidar techniques to time-of-flight range imaging

authors: Whyte, Refael

subjects: Science & Technology

abstract: Amplitude modulated continuous wave (AMCW) time-of flight (ToF) range imaging cameras measure distance by illuminating the scene with amplitude modulated light and measuring the phase difference between the transmitted and reflected modulation envelope. This method of optical range measurement suffers from errors caused by multiple propagation paths, motion, phase wrapping and non-ideal amplitude modulation. In this paper a ToF camera is modified to operate in modes analogous to continuous wave (CW) and stepped frequency continuous wave (SFCW) lidar. In CW operation the velocity of objects can be measured. CW measurement of velocity was linear with true velocity (R² = 0.9969). Qualitative analysis of a complex scene confirms that range measured by SFCW is resilient to errors caused by multiple propagation paths, phase wrapping and non-ideal amplitude modulation which plague AMCW operation. In viewing a complicated scene through a translucent sheet, quantitative comparison of AMCW with SFCW demonstrated a reduction in the median error from −1.3 m to −0.06 m with inter-quartile range of error reduced from 4.0 m to 0.18 m.

text: Application of lidar techniques to time-of-flight range imaging Amplitude modulated continuous wave (AMCW) time-of flight (ToF) range imaging cameras measure distance by illuminating the scene with amplitude modulated light and measuring the phase difference between the transmitted and reflected modulation envelope. This method of optical range measurement suffers from errors caused by multiple propagation paths, motion, phase wrapping and non-ideal amplitude modulation. In this paper a ToF camera is modified to operate in modes analogous to continuous wave (CW) and stepped frequency continuous wave (SFCW) lidar. In CW operation the velocity of objects can be measured. CW measurement of velocity was linear with true velocity (R² = 0.9969). Qualitative analysis of a complex scene confirms that range measured by SFCW is resilient to errors caused by multiple propagation paths, phase wrapping and non-ideal amplitude modulation which plague AMCW operation. In viewing a complicated scene through a translucent sheet, quantitative comparison of AMCW with SFCW demonstrated a reduction in the median error from −1.3 m to −0.06 m with inter-quartile range of error reduced from 4.0 m to 0.18 m.

year: 2015

title: Life in a clinical diploma course

authors: Paterson, Keriata

subjects: Maori

abstract: This paper focuses on the author’s experience of a Clinical Diploma programme. The author is a Maori woman who is in her second year of a three year post-graduate Clinical Diploma programme. The paper includes comment on the cultural focus of content, culture conflicts and areas where the programme might be improved for Maori students.

text: Life in a clinical diploma course This paper focuses on the author’s experience of a Clinical Diploma programme. The author is a Maori woman who is in her second year of a three year post-graduate Clinical Diploma programme. The paper includes comment on the cultural focus of content, culture conflicts and areas where the programme might be improved for Maori students.

year: 1993