title: Stratigraphy and sedimentology of Pliocene strata in the forearc basin (Waikoau and Waikari River catchments), northern Hawke's Bay

authors: Graafhuis, Rhys B.

subjects: Sediments

abstract: An area of over 250 km² in northern Hawke's Bay has been geologically mapped at a scale of 1:50 000, and over 1350 m of Pliocene sedimentary section described and interpreted in the Waikoau and Waikari River catchments. Two new formations and 13 members have been defined, and two formations redefined. The strata show little structural deformation
and form a shallow to moderately dipping (5°- 25°) succession on the uplifted limb of the Hawke's Bay Monocline. The rocks are of Pliocene age, ranging from Opoitian to Nukumaruan. The formations show rapid changes in thickness and lithology along strike from the southwest to the northeast, which is oblique to the depositional paleoslope.
Coarse-grained lithologies such as conglomerates and limestones typically become finergrained, less continuous and thinner towards the northeast.

In ascending order the new formations ( except where redefined) are: Titiokura Formation, Rangiora Formation, Matahorua Formation (redefined) and Waipunga Formation
(redefined). Titiokura Formation is dominated by calcareous siliciclastic sandstone and sandy limestone. The Rangiora Formation and Waipunga Formations are siliciclastic
sandstone and siltstone dominated. Matahorua Formation is dominated by siliciclastic sandstone and greywacke conglomerate.

Lithofacies analysis has been applied to the strata to establish the deposition paleoenvironments. Four lithofacies associations (siltstone, sandstone, conglomerate and
limestone) and 13 lithofacies have been identified. Interpreted bathymetric ranges for the siltstone association ranges from inner to outer shelf. The sandstone association is
characterised by massive to tabular cross-bedded sandstone interpreted to have been deposited on a shoreface to innershelf setting; storm current and tidally emplaced
tempestites and tidalities were deposited on the lower-shoreface to mid shelf; massive to horizontally bedded sandstone and silty beds were deposited on the inner-mid shelf.
Conglomerate associations are characterised by non-marine greywacke conglomerates deposited on a broad braidplain. Sandstone, siltstone and pumice conglomerate all within a
calcareous sandy matrix, are interpreted to have been deposited in tidal channels or on a beachface. The limestone association is characterised thick successions (10 - 50 m) of
sandy coquina that probably formed on the inner shelf possibly on a structural high as carbonate source areas. Thinner correlative units (50 cm - 6 m) of trough cross-bedded
sandy coquina accumulated in inner-mid shelf environments, having been reworked across the shelf from the carbonate source areas.

The successions in the four stratigraphic formations have been interpreted within a sequence stratigraphic framework and 25 sequences have been identified. Interpretation of
sequence boundaries is based on observed unconformities between lithologies, inferred unconformities between lithologies of differing paleoenvironments, and correlative
conformities.

Four typical sequence stratigraphic motifs have been interpreted from these formations. Each motif comprises three or four systems tracts: trangressive (TST), highstand (HST),
regressive (RST) and lowstand system tracts (LST). Motif 1 is representative of the Titiokura Formation, and consists of sandstone and mud drapes (TST and HST), with 
sandstone grading up into limestone (RST) having unconformable tops. Motif 2 is represent by the Rangiora Formation. This formation is comprised of thick successions
(100 m +) of interbedded sandstone and siltstone (TST), siltstone (HST), and siltstone coarsening up into sandstone (RST). The boundary on top of the RST sandstone is typically
unconformable. Motif 3 occurs in the Matahorua Formation. Siltstone or sandstone (TST), sandstone (HST), and interbedded siltstone and sandstone (RST) coarsen up into
greywacke conglomerate (LST). The sequence boundary usually lies within the top of the conglomerate between the coarse massive part and finer bedded conglomerate commonly having a heterogeneous silty-sand matrix; rarely the sequence boundary is at the vert top of the conglomerate unit. Motif 4 is represented by the Waipunga Formation. It is characterized by thin successions (10 m) of interbedded siltstone and sandstone (TST, HST) coarsening upward into sandstone (HST).

The stratigraphic evolution of each of these motifs has been interpreted within the context of an across shelf profile. Evolution of the motifs during a sea-level transgression, is
generally one of limestone deposition near the highstand shoreline. Thinly bedded tidalities, parasequences and massive sandstone with a weak backlap shellbed occur basinward in the TST. Limestone deposition near the highstand shoreline, and siltstone and thickly bedded tidalities basinward, characterise deposition during a sea-level highstand. Erosion and reworking of sediments basinwards during falling sea level conditions result in the formation of erosional sequence boundaries and the accumulation of a regressive sediment
wedge (RST). Sea-level lowstands are characterised by the deposition by greywacke conglomerate on a non-marine braidplain.

The Pliocene sedimentary succession on the western limb of the Hawke's Bay Monocline is interpreted as having been deposited in a steadily subsiding seaway (forearc basin) with uplift on its western margin. Strong storm and tidal currents reworked sediment from shallow into deeper water across a shelf. The siliciclastic sediment was sourced from
erosion in the hinterland. The compressive component within the plate boundary zone in North Island, increased around 2-3 Ma, resulting in uplift of the Axial Ranges, which
became a major sediment source. Sea-level fluctuations throughout the deposition of the sedimentary succession in the study area resulted in the development of cyclothems. The
periodicity of the cycles appears to increase from the Opoitian to the Nukumaruan, for which 6th order (41 ka) cyclicity is inferred. The bathymetric range of the cyclothems also
appears to increase from the Opoitian to Nukumaruan.

text: Stratigraphy and sedimentology of Pliocene strata in the forearc basin (Waikoau and Waikari River catchments), northern Hawke's Bay An area of over 250 km² in northern Hawke's Bay has been geologically mapped at a scale of 1:50 000, and over 1350 m of Pliocene sedimentary section described and interpreted in the Waikoau and Waikari River catchments. Two new formations and 13 members have been defined, and two formations redefined. The strata show little structural deformation
and form a shallow to moderately dipping (5°- 25°) succession on the uplifted limb of the Hawke's Bay Monocline. The rocks are of Pliocene age, ranging from Opoitian to Nukumaruan. The formations show rapid changes in thickness and lithology along strike from the southwest to the northeast, which is oblique to the depositional paleoslope.
Coarse-grained lithologies such as conglomerates and limestones typically become finergrained, less continuous and thinner towards the northeast.

In ascending order the new formations ( except where redefined) are: Titiokura Formation, Rangiora Formation, Matahorua Formation (redefined) and Waipunga Formation
(redefined). Titiokura Formation is dominated by calcareous siliciclastic sandstone and sandy limestone. The Rangiora Formation and Waipunga Formations are siliciclastic
sandstone and siltstone dominated. Matahorua Formation is dominated by siliciclastic sandstone and greywacke conglomerate.

Lithofacies analysis has been applied to the strata to establish the deposition paleoenvironments. Four lithofacies associations (siltstone, sandstone, conglomerate and
limestone) and 13 lithofacies have been identified. Interpreted bathymetric ranges for the siltstone association ranges from inner to outer shelf. The sandstone association is
characterised by massive to tabular cross-bedded sandstone interpreted to have been deposited on a shoreface to innershelf setting; storm current and tidally emplaced
tempestites and tidalities were deposited on the lower-shoreface to mid shelf; massive to horizontally bedded sandstone and silty beds were deposited on the inner-mid shelf.
Conglomerate associations are characterised by non-marine greywacke conglomerates deposited on a broad braidplain. Sandstone, siltstone and pumice conglomerate all within a
calcareous sandy matrix, are interpreted to have been deposited in tidal channels or on a beachface. The limestone association is characterised thick successions (10 - 50 m) of
sandy coquina that probably formed on the inner shelf possibly on a structural high as carbonate source areas. Thinner correlative units (50 cm - 6 m) of trough cross-bedded
sandy coquina accumulated in inner-mid shelf environments, having been reworked across the shelf from the carbonate source areas.

The successions in the four stratigraphic formations have been interpreted within a sequence stratigraphic framework and 25 sequences have been identified. Interpretation of
sequence boundaries is based on observed unconformities between lithologies, inferred unconformities between lithologies of differing paleoenvironments, and correlative
conformities.

Four typical sequence stratigraphic motifs have been interpreted from these formations. Each motif comprises three or four systems tracts: trangressive (TST), highstand (HST),
regressive (RST) and lowstand system tracts (LST). Motif 1 is representative of the Titiokura Formation, and consists of sandstone and mud drapes (TST and HST), with 
sandstone grading up into limestone (RST) having unconformable tops. Motif 2 is represent by the Rangiora Formation. This formation is comprised of thick successions
(100 m +) of interbedded sandstone and siltstone (TST), siltstone (HST), and siltstone coarsening up into sandstone (RST). The boundary on top of the RST sandstone is typically
unconformable. Motif 3 occurs in the Matahorua Formation. Siltstone or sandstone (TST), sandstone (HST), and interbedded siltstone and sandstone (RST) coarsen up into
greywacke conglomerate (LST). The sequence boundary usually lies within the top of the conglomerate between the coarse massive part and finer bedded conglomerate commonly having a heterogeneous silty-sand matrix; rarely the sequence boundary is at the vert top of the conglomerate unit. Motif 4 is represented by the Waipunga Formation. It is characterized by thin successions (10 m) of interbedded siltstone and sandstone (TST, HST) coarsening upward into sandstone (HST).

The stratigraphic evolution of each of these motifs has been interpreted within the context of an across shelf profile. Evolution of the motifs during a sea-level transgression, is
generally one of limestone deposition near the highstand shoreline. Thinly bedded tidalities, parasequences and massive sandstone with a weak backlap shellbed occur basinward in the TST. Limestone deposition near the highstand shoreline, and siltstone and thickly bedded tidalities basinward, characterise deposition during a sea-level highstand. Erosion and reworking of sediments basinwards during falling sea level conditions result in the formation of erosional sequence boundaries and the accumulation of a regressive sediment
wedge (RST). Sea-level lowstands are characterised by the deposition by greywacke conglomerate on a non-marine braidplain.

The Pliocene sedimentary succession on the western limb of the Hawke's Bay Monocline is interpreted as having been deposited in a steadily subsiding seaway (forearc basin) with uplift on its western margin. Strong storm and tidal currents reworked sediment from shallow into deeper water across a shelf. The siliciclastic sediment was sourced from
erosion in the hinterland. The compressive component within the plate boundary zone in North Island, increased around 2-3 Ma, resulting in uplift of the Axial Ranges, which
became a major sediment source. Sea-level fluctuations throughout the deposition of the sedimentary succession in the study area resulted in the development of cyclothems. The
periodicity of the cycles appears to increase from the Opoitian to the Nukumaruan, for which 6th order (41 ka) cyclicity is inferred. The bathymetric range of the cyclothems also
appears to increase from the Opoitian to Nukumaruan.

year: 2001

title: Dynamic Electroporation Modelling

authors: Talele, Sadhana

subjects: electroporation

abstract: In this thesis, modelling and simulation of the effects of electric fields on a single spherical cell are undertaken. Of interest is the effect that different electric field waveforms have on the induced transmembrane potential of the cell and by consequence the electropermeabilization of the cell membrane in terms of pore density or the fraction of the cell area that the pores occupy. Conventional biotechnology processes of electroporation make use of unipolar electric field pulses, which are known to generate undesirable conditions such as asymmetrical electropermeabilization. These electrical protocols also contribute to lower efficiencies in electroporation based applications (in terms of uptake of molecules in the cell) by being sensitive to cell radii.

Until recently, theoretical models of electroporation have lagged behind the experimental research. In order to optimize the efficiency of electroporation, it is important to consider as many biological and physical aspects as possible and it is a necessity that a variety of electric pulse parameters be tested. Thus a comprehensive model which can predict electropermeabilization as a result of any form of applied electric field and other important electroporation parameters is necessary. None of the existing theoretical modelling studies present simulations of dynamic electroporation modelling as a cell response to bipolar electric field wave-shapes. Developing such a model is the aim of this thesis.

In this thesis two numerical models are developed. These models consider electroporation as a dynamic process and include the non-linear dynamic effects of membrane electropermeabilization. The first model assumes all pores are identical and small (0.76~nm radius) and is capable of simulating transmembrane potential and pore density temporally and spatially, given any form of applied electric field and other important electroporation system parameters such as external medium, membrane, and cytoplasm complex dielectric properties. The piece-wise step response model presented here is used to simulate cell response to several different applied electric field wave-shape pulses.% including a unipolar square wave, bipolar square wave, bipolar sine wave, bipolar rectangular wave (rectangular pulse train), and a bipolar triangular wave.

Additional results from the first model demonstrate how the efficiency of electroporation related applications can be significantly improved by appropriately adjusting the parameters of the applied electric field and the  extracellular conductivity. Emphasis is given on the normalization of the degree of electroporation (in terms of pore density) for  two  cell radii (7.5~$\mu$m and 15~$\mu$m).

Although, these results gave a fair indication of the extent of electroporation in terms of pore density, the approximation that all pores have the same size, and do not change with time, may not be  appropriate. There is a need to model electroporation so as to reflect the growth or shrinkage of pores with time, as well as efficiently handle arbitrary waveshapes of electric fields. The additional information about pore radius evolution  gives a more realistic picture of the extent of electroporation, especially if one is to model for longer time (longer than 1~$\mu$s) or if an application necessarily required existence of larger pores (radius lager than 1~nm) rather than just the total pore area. Pore radius and pore numbers  affect the transmembrane potential, which in turn  affects pore density and pore radius.
Literature includes information on spatial and temporal aspects of pore radius evolution. However, the electric fields used in these models were limited to unipolar DC pulses and details of temporal and spatial evolution of transmembrane potential and pore radius have not been reported.
 
The second model developed in this thesis   simulates  spatial and temporal aspects of pore radius as an effect of  any given form  of applied electric field (including unipolar or bipolar), and other important electroporation system parameters.   The transmembrane potential and pore radii as function of time and angular position about the cell membrane   are presented. The results show that pore  radii    tend to be more normalized when an AC (bipolar)    field is used when compared to a  DC (unipolar) field (pore radii ranging from 1~nm to 8~nm for DC protocol compared with 1~nm to 3.4~nm for AC protocol when  the pulse amplitude used in both  cases is such as to give a similar fractional pore area at the end of 2~$\mu$s).
 
Additional simulation results from this model are  used to  compare the extent of electroporation   in response to sinusoidal AC (bipolar) electric field pulses of two different frequencies in a range of extracellular conductivity for two different cell radii (7.5~$\mu$m and 15~$\mu$m). 
It is   observed that  a higher frequency (1~MHz) bipolar sinusoidal applied electric field pulse reduces the relative difference in fractional pore area   for the two cell sizes compared to a lower frequency  (100~kHz) pulse. Nevertheless for the high frequency, a significantly higher amplitude is required to create the same level of average fractional pore area. Asymmetry of fractional pore area between the two hemispheres of the cell is observed for both field protocols.

text: Dynamic Electroporation Modelling In this thesis, modelling and simulation of the effects of electric fields on a single spherical cell are undertaken. Of interest is the effect that different electric field waveforms have on the induced transmembrane potential of the cell and by consequence the electropermeabilization of the cell membrane in terms of pore density or the fraction of the cell area that the pores occupy. Conventional biotechnology processes of electroporation make use of unipolar electric field pulses, which are known to generate undesirable conditions such as asymmetrical electropermeabilization. These electrical protocols also contribute to lower efficiencies in electroporation based applications (in terms of uptake of molecules in the cell) by being sensitive to cell radii.

Until recently, theoretical models of electroporation have lagged behind the experimental research. In order to optimize the efficiency of electroporation, it is important to consider as many biological and physical aspects as possible and it is a necessity that a variety of electric pulse parameters be tested. Thus a comprehensive model which can predict electropermeabilization as a result of any form of applied electric field and other important electroporation parameters is necessary. None of the existing theoretical modelling studies present simulations of dynamic electroporation modelling as a cell response to bipolar electric field wave-shapes. Developing such a model is the aim of this thesis.

In this thesis two numerical models are developed. These models consider electroporation as a dynamic process and include the non-linear dynamic effects of membrane electropermeabilization. The first model assumes all pores are identical and small (0.76~nm radius) and is capable of simulating transmembrane potential and pore density temporally and spatially, given any form of applied electric field and other important electroporation system parameters such as external medium, membrane, and cytoplasm complex dielectric properties. The piece-wise step response model presented here is used to simulate cell response to several different applied electric field wave-shape pulses.% including a unipolar square wave, bipolar square wave, bipolar sine wave, bipolar rectangular wave (rectangular pulse train), and a bipolar triangular wave.

Additional results from the first model demonstrate how the efficiency of electroporation related applications can be significantly improved by appropriately adjusting the parameters of the applied electric field and the  extracellular conductivity. Emphasis is given on the normalization of the degree of electroporation (in terms of pore density) for  two  cell radii (7.5~$\mu$m and 15~$\mu$m).

Although, these results gave a fair indication of the extent of electroporation in terms of pore density, the approximation that all pores have the same size, and do not change with time, may not be  appropriate. There is a need to model electroporation so as to reflect the growth or shrinkage of pores with time, as well as efficiently handle arbitrary waveshapes of electric fields. The additional information about pore radius evolution  gives a more realistic picture of the extent of electroporation, especially if one is to model for longer time (longer than 1~$\mu$s) or if an application necessarily required existence of larger pores (radius lager than 1~nm) rather than just the total pore area. Pore radius and pore numbers  affect the transmembrane potential, which in turn  affects pore density and pore radius.
Literature includes information on spatial and temporal aspects of pore radius evolution. However, the electric fields used in these models were limited to unipolar DC pulses and details of temporal and spatial evolution of transmembrane potential and pore radius have not been reported.
 
The second model developed in this thesis   simulates  spatial and temporal aspects of pore radius as an effect of  any given form  of applied electric field (including unipolar or bipolar), and other important electroporation system parameters.   The transmembrane potential and pore radii as function of time and angular position about the cell membrane   are presented. The results show that pore  radii    tend to be more normalized when an AC (bipolar)    field is used when compared to a  DC (unipolar) field (pore radii ranging from 1~nm to 8~nm for DC protocol compared with 1~nm to 3.4~nm for AC protocol when  the pulse amplitude used in both  cases is such as to give a similar fractional pore area at the end of 2~$\mu$s).
 
Additional simulation results from this model are  used to  compare the extent of electroporation   in response to sinusoidal AC (bipolar) electric field pulses of two different frequencies in a range of extracellular conductivity for two different cell radii (7.5~$\mu$m and 15~$\mu$m). 
It is   observed that  a higher frequency (1~MHz) bipolar sinusoidal applied electric field pulse reduces the relative difference in fractional pore area   for the two cell sizes compared to a lower frequency  (100~kHz) pulse. Nevertheless for the high frequency, a significantly higher amplitude is required to create the same level of average fractional pore area. Asymmetry of fractional pore area between the two hemispheres of the cell is observed for both field protocols.

year: 2009

title: La gouvernance des rivières en Nouvelle-Zélande : une solution élégante ?

authors: Te Aho, Linda

subjects: Water governance,

abstract: Governance of Water in New Zealand: An Elegant Solution? This chapter is grounded in the context of Aotearoa New Zealand while drawing on larger references, such as the United Nations Declaration on the Rights of Indigenous peoples, the Rio+20 Declaration and constitutional provisions for Rights of Nature. The chapter analyses a proposed new model for the contentious issue of freshwater governance in New Zealand based on responsible use which also addresses the complex world of state-Māori relations.

text: La gouvernance des rivières en Nouvelle-Zélande : une solution élégante ? Governance of Water in New Zealand: An Elegant Solution? This chapter is grounded in the context of Aotearoa New Zealand while drawing on larger references, such as the United Nations Declaration on the Rights of Indigenous peoples, the Rio+20 Declaration and constitutional provisions for Rights of Nature. The chapter analyses a proposed new model for the contentious issue of freshwater governance in New Zealand based on responsible use which also addresses the complex world of state-Māori relations.

year: 2018