title: Characterisation and paleoclimatic signals within tephric loess deposits aged between c. 33 to 9.5 cal ka in the Rotorua area, northern New Zealand

authors: Lanigan, Kerri Miriam

subjects: tephrochronology

abstract: I studied tephric loess deposits aged between c. 33 and 9.5 cal ka in the Rotorua region, north-east central North Island. I produced a stratigraphic framework for the loess deposits and characterised them using a range of field and laboratory methods to develop a multi-proxy paleoclimatic reconstruction for the region. A number of key tephra marker layers, including Kawakawa (c. 25.4 cal ka), Te Rere (c. 25.2 cal ka), Okareka (c. 21.9 cal ka), Rerewhakaaitu (c. 17.5 cal ka), Rotorua (c. 15.6 cal ka), Waiohau (c. 13.6 cal ka) and Rotoma (c. 9.5 cal ka) tephras, were used as isochronous tie-points within the loess deposits and to provide ages within the loess. In contrast to those of previous studies, the findings from my study suggest that loess deposition continued at some sites in the Rotorua region until c. 9.5 cal ka. The average rate of loess accumulation was about 2.3 cm per century. The thickest loess sequence deposited between c. 33 and 9.5 cal ka was about 4.3 metres (tephra-free thickness) at Dansey Rd. In general, the tephric loess deposits are largely massive, silty and often yellowish brown, dull yellowish brown or dull yellow orange in colour (Munsell colour codes 10YR 5/4, 5/6, 5/8 or 6/4). Paleoclimate proxy analyses of the loess included grain size, accumulation rates, phytolith analysis, magnetic susceptibility, total carbon content, carbon isotopes and potassium content. 

The results from my study suggest that the Rotorua region underwent a change from relatively warm, wet and less windy interstadial conditions to relatively cold, dry and more windy stadial conditions (indicative of the beginning of the extended-last glacial maximum) at c. 25.4 cal ka (about the time of deposition of the Kawakawa Tephra). Between c. 25.4 and 18.4 cal ka, stadial conditions likely dominated, although climate was also variable, and results suggest that two short-lived interstadials, centred around c. 23 cal ka and c. 21 cal ka, may have occurred. Stadial conditions appear to have ended at c. 18.4 cal ka when conditions became relatively warmer, wetter and less windy (likely indicative of last glacial – interglacial transition conditions). However, during these warming conditions, between c. 13.8—12.8 cal ka, results suggest that conditions became temporarily relatively cooler and drier (indicative of the late glacial reversal). In general, there is good support from the New Zealand climate event stratigraphy (CES) (D.J. Barrell and others in preparation. “The sequence of climatic events in New Zealand over the past 30 000 years – a composite stratotype for regional correlation and comparison.” Quaternary Science Reviews [Australasian INTIMATE issue]) and other North Island paleoclimate records for these three broad changes in climate from interstadial to stadial and back to interstadial (and possibly interglacial) conditions during this time. However, the exact timing of these broad changes as well as that of the shorter-lived climatic variations are not perfectly synchronised with the timing of similar changes in the CES and other North Island records.

text: Characterisation and paleoclimatic signals within tephric loess deposits aged between c. 33 to 9.5 cal ka in the Rotorua area, northern New Zealand I studied tephric loess deposits aged between c. 33 and 9.5 cal ka in the Rotorua region, north-east central North Island. I produced a stratigraphic framework for the loess deposits and characterised them using a range of field and laboratory methods to develop a multi-proxy paleoclimatic reconstruction for the region. A number of key tephra marker layers, including Kawakawa (c. 25.4 cal ka), Te Rere (c. 25.2 cal ka), Okareka (c. 21.9 cal ka), Rerewhakaaitu (c. 17.5 cal ka), Rotorua (c. 15.6 cal ka), Waiohau (c. 13.6 cal ka) and Rotoma (c. 9.5 cal ka) tephras, were used as isochronous tie-points within the loess deposits and to provide ages within the loess. In contrast to those of previous studies, the findings from my study suggest that loess deposition continued at some sites in the Rotorua region until c. 9.5 cal ka. The average rate of loess accumulation was about 2.3 cm per century. The thickest loess sequence deposited between c. 33 and 9.5 cal ka was about 4.3 metres (tephra-free thickness) at Dansey Rd. In general, the tephric loess deposits are largely massive, silty and often yellowish brown, dull yellowish brown or dull yellow orange in colour (Munsell colour codes 10YR 5/4, 5/6, 5/8 or 6/4). Paleoclimate proxy analyses of the loess included grain size, accumulation rates, phytolith analysis, magnetic susceptibility, total carbon content, carbon isotopes and potassium content. 

The results from my study suggest that the Rotorua region underwent a change from relatively warm, wet and less windy interstadial conditions to relatively cold, dry and more windy stadial conditions (indicative of the beginning of the extended-last glacial maximum) at c. 25.4 cal ka (about the time of deposition of the Kawakawa Tephra). Between c. 25.4 and 18.4 cal ka, stadial conditions likely dominated, although climate was also variable, and results suggest that two short-lived interstadials, centred around c. 23 cal ka and c. 21 cal ka, may have occurred. Stadial conditions appear to have ended at c. 18.4 cal ka when conditions became relatively warmer, wetter and less windy (likely indicative of last glacial – interglacial transition conditions). However, during these warming conditions, between c. 13.8—12.8 cal ka, results suggest that conditions became temporarily relatively cooler and drier (indicative of the late glacial reversal). In general, there is good support from the New Zealand climate event stratigraphy (CES) (D.J. Barrell and others in preparation. “The sequence of climatic events in New Zealand over the past 30 000 years – a composite stratotype for regional correlation and comparison.” Quaternary Science Reviews [Australasian INTIMATE issue]) and other North Island paleoclimate records for these three broad changes in climate from interstadial to stadial and back to interstadial (and possibly interglacial) conditions during this time. However, the exact timing of these broad changes as well as that of the shorter-lived climatic variations are not perfectly synchronised with the timing of similar changes in the CES and other North Island records.

year: 2012

title: The change in the horizontal position of the dune toe and vegetation line on beaches within the Waikato Region

authors: Davies-Calway, Celeste Jade

subjects: dune toe

abstract: Beaches are highly variable landscapes that are constantly changing in response to a range of climatic variables. For example, local wind can cause the movement of sand across the beach and accretion, whilst storms that occur far from the beach create waves and surges which also changes the shape and morphology of the beach. The lower beach face is inundated for longer during a tidal cycle and therefore is subjected more often to wave action conversely, the upper part of the beach is inundated less often and therefore is less affected by wave energy. When storms occur, water levels are higher along the beach, waves are brought into contact with the upper beach face and erosion occurs. This erosion causes escarpment of the dune face and landward movement of the beach face, where sand is transported to offshore bars in the surf zone. Changes also occur during fair weather conditions where accretion occurs across the beach face and dune area and sand is transported back up onto the beach and sand dunes.

Beach morphology has traditionally been monitored using beach profiles, however new methods are emerging that provide more information with the potential for greater spatial and temporal data collection. In New Zealand the vegetation line and the position of the dune toe is often used as a proxy for the shoreline and setback distances are measured relative to this feature. Beach morphodynamics have been studied extensively but typical monitoring and predictive methods are not optimised to track and predict changes in the dune toe position. Beach profile surveys are the most common and reliable monitoring method used for monitoring beaches and they are used extensively throughout the world. Although beach profiles give valuable information on several different aspects of beach processes, they may not be the optimal method for tracking dune toe movement and there are other methods that might be more effective.

The aim of the research was to provide information to help optimise the monitoring and prediction of changes in the dune toe by determining: (i) the horizontal and vertical variation of the dune toe to establish how often the horizontal and vertical position of the sand dune toe changes, (ii) the alongshore variation of the dune toe along the beach length, (iii) what causes the changes in the dune toe, (iv) compare using the dune toe for beach monitoring with traditional beach monitoring methods, (v) testing different methods to measure the dune toe and vegetation line, (vi) predicting the dune toe in the future using a model. The main study sites for the research were Whangapoua Beach, Matarangi Beach, Buffalo Beach, Hot Water Beach and Tairua beach of eastern Coromandel Peninsula, and Ngarunui Beach, Raglan, where field surveys were conducted. An historical dataset of beach profiles from 20 Eastern Coromandel beaches were analysed for long term patterns. A new method for measuring dune toe using video analysis and a model for predicting the future dune toe changes was tested at Tairua Beach, Coromandel Peninsula.

The results show that, from the field survey of beach profiles, there was low variability at the dune toe compared with further down the beach. The range of distribution of the vegetation line was larger than the range of distribution for the dune toe and the dune toe was generally more seaward than the vegetation line. The vegetation line was generally not at the same location as the dune toe which has strong implications for using vegetation as a measure of dune movement. The alongshore dune toe underwent small changes throughout the survey period and there was alongshore variation of the dune toe, along with changes in the dune toe horizontal position and height of the dune toe throughout the year survey period, which was expected. Video analysis was shown to be a potential new technique for measuring the vegetation line which could be used for beach monitoring. A model was used to predict the change in the dune toe, and it predicted that there was no change in the dune toe between 1998 and 2011; however, the analysis of the imagery showed there were numerous occasions where water reached the dune toe and therefore erosion of the dune toe occurred.

text: The change in the horizontal position of the dune toe and vegetation line on beaches within the Waikato Region Beaches are highly variable landscapes that are constantly changing in response to a range of climatic variables. For example, local wind can cause the movement of sand across the beach and accretion, whilst storms that occur far from the beach create waves and surges which also changes the shape and morphology of the beach. The lower beach face is inundated for longer during a tidal cycle and therefore is subjected more often to wave action conversely, the upper part of the beach is inundated less often and therefore is less affected by wave energy. When storms occur, water levels are higher along the beach, waves are brought into contact with the upper beach face and erosion occurs. This erosion causes escarpment of the dune face and landward movement of the beach face, where sand is transported to offshore bars in the surf zone. Changes also occur during fair weather conditions where accretion occurs across the beach face and dune area and sand is transported back up onto the beach and sand dunes.

Beach morphology has traditionally been monitored using beach profiles, however new methods are emerging that provide more information with the potential for greater spatial and temporal data collection. In New Zealand the vegetation line and the position of the dune toe is often used as a proxy for the shoreline and setback distances are measured relative to this feature. Beach morphodynamics have been studied extensively but typical monitoring and predictive methods are not optimised to track and predict changes in the dune toe position. Beach profile surveys are the most common and reliable monitoring method used for monitoring beaches and they are used extensively throughout the world. Although beach profiles give valuable information on several different aspects of beach processes, they may not be the optimal method for tracking dune toe movement and there are other methods that might be more effective.

The aim of the research was to provide information to help optimise the monitoring and prediction of changes in the dune toe by determining: (i) the horizontal and vertical variation of the dune toe to establish how often the horizontal and vertical position of the sand dune toe changes, (ii) the alongshore variation of the dune toe along the beach length, (iii) what causes the changes in the dune toe, (iv) compare using the dune toe for beach monitoring with traditional beach monitoring methods, (v) testing different methods to measure the dune toe and vegetation line, (vi) predicting the dune toe in the future using a model. The main study sites for the research were Whangapoua Beach, Matarangi Beach, Buffalo Beach, Hot Water Beach and Tairua beach of eastern Coromandel Peninsula, and Ngarunui Beach, Raglan, where field surveys were conducted. An historical dataset of beach profiles from 20 Eastern Coromandel beaches were analysed for long term patterns. A new method for measuring dune toe using video analysis and a model for predicting the future dune toe changes was tested at Tairua Beach, Coromandel Peninsula.

The results show that, from the field survey of beach profiles, there was low variability at the dune toe compared with further down the beach. The range of distribution of the vegetation line was larger than the range of distribution for the dune toe and the dune toe was generally more seaward than the vegetation line. The vegetation line was generally not at the same location as the dune toe which has strong implications for using vegetation as a measure of dune movement. The alongshore dune toe underwent small changes throughout the survey period and there was alongshore variation of the dune toe, along with changes in the dune toe horizontal position and height of the dune toe throughout the year survey period, which was expected. Video analysis was shown to be a potential new technique for measuring the vegetation line which could be used for beach monitoring. A model was used to predict the change in the dune toe, and it predicted that there was no change in the dune toe between 1998 and 2011; however, the analysis of the imagery showed there were numerous occasions where water reached the dune toe and therefore erosion of the dune toe occurred.

year: 2020

title: Discussing future directions in the Maori legal environment

authors: Te Aho, Linda

abstract: The next few years are likely to be exciting in terms of law changes, parliament getting ready for the next election cycle and the end of historical claims settlements. This presentation will look at the future of the Maori legal environment

text: Discussing future directions in the Maori legal environment The next few years are likely to be exciting in terms of law changes, parliament getting ready for the next election cycle and the end of historical claims settlements. This presentation will look at the future of the Maori legal environment

year: 2016