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: New MRI-safe Implant Electrode Design

authors: McCabe, Steven Owen

subjects: Science & Technology

abstract: Medical implants often prevent patients having Magnetic Resonance Imaging (MRI) scans because the leads behave as antennas with respect to the RF excitation and cause hazardous heating in neural tissue. This manuscript describes an approach that virtually eliminates the risk of RF heating by means of easily-incorporated, mutually-coupled filars. The resulting leads need be neither physically larger nor significantly more costly than existing designs. Combined with thin insulation and surface roughening techniques, this manuscript represents the first complete release of recently-patented technologies. Both simulations and measurements at 128MHz are presented to confirm performance in 3-Tesla MRI machines.

text: New MRI-safe Implant Electrode Design Medical implants often prevent patients having Magnetic Resonance Imaging (MRI) scans because the leads behave as antennas with respect to the RF excitation and cause hazardous heating in neural tissue. This manuscript describes an approach that virtually eliminates the risk of RF heating by means of easily-incorporated, mutually-coupled filars. The resulting leads need be neither physically larger nor significantly more costly than existing designs. Combined with thin insulation and surface roughening techniques, this manuscript represents the first complete release of recently-patented technologies. Both simulations and measurements at 128MHz are presented to confirm performance in 3-Tesla MRI machines.

year: 2016-01-01

title: Ka moemoeā o koutou kaumatua...

authors: Whitiaua, Ropitini

subjects: Ruatāhuna

abstract: Founded by the spiritual leader and prophet Te Kooti Te Turuki Arikirangi, the Ringatū faith came into existence in the 1870s during a very turbulent time for Māori. Struggling for survival many Māori tribes and communities accepted the teachings of Te Kooti and the principles of the Ringatū church as a means of maintaining their independence, beliefs and culture. A truly syncretic religion, the Ringatū church combines traditional Māori customs and beliefs with Christian scriptures forming a religious institution that fits within Christian doctrine while maintaining many important Māori philosophies. 
Throughout the latter stages of the 19th century and into the 20th century the Ringatū faith found fertile soil in many regions and grew in popularity and strength. Areas like the Bay of Plenty and sections of the East Coast became strongholds of the church and to this present day the Ringatū faith still functions within these areas. Therefore it is not surprising that Ruatāhuna, a small and isolated community located in the centre of Te Urewera has been part of the Ringatū movement since its inception. This community sheltered Te Kooti while he was being hunted by government forces, and the people became devout followers of the Ringatū faith. Therefore the proficies of Te Kooti and the principles of the church have become central in the identity and cultural practises of Tūhoe and the community of Ruatāhuna. 
For generations the Ringatū church has been the main spiritual institution within Ruatāhuna, with its gatherings being attended by the vast majority of the community. Its influence has permeated throughout every facet of Ruatāhuna life including spirituality, politics, social controls and even cultural practise. However in the past 30 years there has been a significant decline in the influence and popularity of the Ringatū church, and its tenants are now maintained by just a few families. This decline is most evident during the monthly gatherings of the Ringatū community in Ruatāhuna on the 12 of each month, ‘tekau-mā-rua’, where there are now only about 20 regular attendees. 

This thesis explores the Ringatū faith within Ruatāhuna from its origin, its development through the decades and current position. It examines the changing dynamics of the church in recent times in order to understand why its popularity and influence has shifted. Finally this study seeks a path forward for the Ringatū church in a modern world, looking at how the faith can respond to the needs of a new generation and to find a purpose in a new age.

text: Ka moemoeā o koutou kaumatua... Founded by the spiritual leader and prophet Te Kooti Te Turuki Arikirangi, the Ringatū faith came into existence in the 1870s during a very turbulent time for Māori. Struggling for survival many Māori tribes and communities accepted the teachings of Te Kooti and the principles of the Ringatū church as a means of maintaining their independence, beliefs and culture. A truly syncretic religion, the Ringatū church combines traditional Māori customs and beliefs with Christian scriptures forming a religious institution that fits within Christian doctrine while maintaining many important Māori philosophies. 
Throughout the latter stages of the 19th century and into the 20th century the Ringatū faith found fertile soil in many regions and grew in popularity and strength. Areas like the Bay of Plenty and sections of the East Coast became strongholds of the church and to this present day the Ringatū faith still functions within these areas. Therefore it is not surprising that Ruatāhuna, a small and isolated community located in the centre of Te Urewera has been part of the Ringatū movement since its inception. This community sheltered Te Kooti while he was being hunted by government forces, and the people became devout followers of the Ringatū faith. Therefore the proficies of Te Kooti and the principles of the church have become central in the identity and cultural practises of Tūhoe and the community of Ruatāhuna. 
For generations the Ringatū church has been the main spiritual institution within Ruatāhuna, with its gatherings being attended by the vast majority of the community. Its influence has permeated throughout every facet of Ruatāhuna life including spirituality, politics, social controls and even cultural practise. However in the past 30 years there has been a significant decline in the influence and popularity of the Ringatū church, and its tenants are now maintained by just a few families. This decline is most evident during the monthly gatherings of the Ringatū community in Ruatāhuna on the 12 of each month, ‘tekau-mā-rua’, where there are now only about 20 regular attendees. 

This thesis explores the Ringatū faith within Ruatāhuna from its origin, its development through the decades and current position. It examines the changing dynamics of the church in recent times in order to understand why its popularity and influence has shifted. Finally this study seeks a path forward for the Ringatū church in a modern world, looking at how the faith can respond to the needs of a new generation and to find a purpose in a new age.

year: 2015