1,721,224 research outputs found
Using Pollen Records from New Zealand and Southern Chile to Reconstruct New Zealand Climate Variability over the Last 14,000 years
No full textClimate variability in New Zealand (34-47°S), a long, narrow continental strip straddling the mid-latitudes of the Southern Hemisphere, results largely from the interplay between sub-tropical and sub-Antarctic atmospheric and oceanic circulation systems. Despite their importance to present-day New Zealand climate, these hemispheric-wide systems have only recently come under the spotlight of paleo-climate investigations with most attention having traditionally been centred on reconstructing climate trends. This PhD adopts a broader approach to climate reconstruction, by developing and comparing two new pollen-climate reconstructions from New Zealand (38-42°S) and one from Patagonia, Southern Chile (43°S). At each site, paleo-climate interpretations are based on the changes in climate-sensitive plant indicators. The influence of hemispheric atmospheric circulation on New Zealand climate history is assessed by: (1) comparing New Zealand climate/vegetation trends with published proxies from low- and high-latitudes, and (2) comparing New Zealand reconstructions with the Patagonian record. Finally, a multi-millennial pattern of Southern Hemisphere circulation over the last 14,000 cal yr BP (calendar years before AD 1950) is outlined.
The first record presented is a 16,000-year temperature reconstruction from a small alpine lake in South Island, New Zealand (41°S), based on pollen and plant macrofossils. Climate variations are interpreted from the relative abundance of lowland and highland vegetation. The results include a lifting of the altitudinal forest limits attributed to warming pulses between 13,000-10,000 cal yr BP and between 7000-6000 cal yr BP, and a decline of lowland relative to upland forest taxa interpreted as cooling trends between 10,000-7000 cal yr BP and over the last 3000 years.
The second record gives 15,000-year temperature and precipitation reconstructions from a peatbog in northern New Zealand (38°S), based on pollen and charcoal analysis. Temperature changes are assessed based on two quantitate reconstructions, whereas precipitation trends are inferred from variations in arboreal taxa with different drought tolerances. A long-term warming is inferred between 14,600-10,000 cal yr BP. Persistent dry conditions are recorded between 12,000-10,000 cal yr BP, followed by a long-term wet period between 10,000-6000 cal yr BP. The last 7000 years feature a long-term drying trend that culminates with persistent drier conditions over the last 3000 years.
The third record provides a 16,000-year reconstruction from a small lake in Northwestern Patagonia (43°S), based on pollen and charcoal analysis. Climate conditions are inferred from the relative variations of pollen types with distinctive climate tolerances and complemented with changes in fire activity. These variations are in turn interpreted as resulting from changes in the position and/or strength of the Southern Westerly Winds (SWW). Cold and moist conditions attributable to stronger/northward-shifted SWW winds are observed between 16,000-13,600 cal yr BP. In contrast, warm and dry conditions suggestive of weaker/southward-shifted SWW are detected between 12,000-10,000 cal yr BP. The last 6000 years shows a trend towards colder conditions and increasing precipitation variability, suggesting a highly variable westerly flow over Patagonia.
A comparison between the New Zealand and the Patagonia records suggest: (1) weakened/southward-shifted westerly flow over the southern mid-latitudes between 13,000-10,000 cal yr BP caused rapid warming and peak temperatures in New Zealand, as well as dry conditions in Northern New Zealand, (2) Enhanced/northward-shifted SWW over the southern mid-latitudes between 9000-4000 cal yr BP caused decreasing temperatures in the South Island and increasing precipitation in Northern New Zealand and (3) Overall weakened/southward-shifted SWW after 4000 cal yr BP caused a decrease in temperature in the southern New Zealand site. Drier conditions in Northern New Zealand and the overall increase in climate instability at all sites may have resulted from more frequent El Niño events along with an increase in sub-tropical climate variability
Investigations of plant subfossil cuticles at a Holocene raised bog complex, northern New Zealand
No full textSubfossil plant cuticles, the very resistant waxy layer covering vascular land plants, are a neglected source of information in peat studies, despite their high preservation and identification potential. A lack of standardised methods and reference material are major contributing factors. In this thesis, a new method is introduced to test if subfossil plant cuticles from Moanatuatua Bog in the northern North Island of New Zealand can give a robust reconstruction of local bog surface vegetation changes during the Holocene. The method was successfully established and applied at coarse sampling resolution to show vegetation changes across the full length of the core and at fine sampling resolution around charcoal layers to reconstruct the post-fire response pattern of the main plant species on the bog. Additionally, bulk density and organic matter analyses were carried out to provide further insight into these changes. At the core site, towards the southern margins of Moanatuatua Bog, swamp forest had developed by 15000 cal yr BP. Until ca. 10500 cal yr BP, the vegetation assemblage was sedge-dominated, indicating swamp and/or fen conditions. A significant increase in macroscopic charcoal particles coincided with the transition to a more diversified vegetation composition. At around 4500 cal yr BP, the vegetation became restiad-dominated, indicating full raised bog conditions. The coarse resolution cuticle results were further compared to a pollen record from the same sequence, which was established independently. This comparison showed that plant subfossil cuticles can provide additional information to pollen analysis in cases where pollen is hard to identify or poorly preserved. Specifically, restiad pollen is hard to differentiate, yet cuticles of Empodisma and Sporadanthus have very distinct features. Also, Cyperaceae pollen is very poorly preserved at Moanatuatua Bog and the Cyperaceae pollen curve shows a poor match with the Cyperaceae cuticle record. It is suggested therefore that Cyperaceae pollen at this site – and potentially other peat sites – is a less reliable indicator of local sedge communities than a Cyperaceae cuticle record. At fine resolution, results were blurred across a time interval that was marginal for reconstructing response patterns due to the constraints imposed by sampling resolution and peat accumulation rate of Moanatuatua Bog. Nevertheless, two out of three charcoal layers recorded a local fire on the bog surface, with one layer displaying the expected vegetation response. After the fire, Empodisma, as a mid-successional species, re-established on the bog surface before Sporadanthus, a late-successional species. The other layer was dominated by sedges and showed no response pattern, as is to be expected due to the very fast recovery of sedges. In general, sample preparation for cuticle analysis proved to be fast with relatively little equipment or chemicals needed. With detailed reference material, identification to species level is possible due to distinctive and pronounced cuticle features. Plant cuticle analysis is therefore proposed to be a reliable tool to reconstruct long-term and short-term vegetation changes from peat sequences
The Last Glacial Maximum and Deglaciation in Southern New Zealand: New Pollen-Climate Reconstructions
No full textThe project builds upon existing knowledge of late Quaternary
palaeoenvironmenta change and tests the recently developed New Zealand
INTIMATE (Integration of Ice Marine and Terrestrial archive) climate event
stratigraphy (NZ-I CES; 30-8 ka). Four pollen and sediment records from three
climatically contrasting regions in the South Island provide a vegetation and
climate history for this area between 38-4 ka. In this study, the Last Glacial Cold
Period (LGCP; c. 31.4-18.9 ka) is characterised by a two step cooling, with the
coldest conditions, reaching possibly >5.3°C cooling, occurring between 21-19 ka,
marking the Last Glacial Maximum. A new precipitation proxy using macrophyte
pollen concentrations at an eastern South Island site suggests dominantly dry
conditions prevailed during the LGCP except for two periods of wetter climate
around 26-24 ka and 21 ka. The dry periods correspond with evidence of glacial
advance, colder environments and possibly increased intensity of the southern
westerlies. Conversely, the wet periods coincide with reduced glacial activity,
milder climates and decreased westerly wind intensity. Deglaciation began
between 18.9-18.4 ka followed by rapid climate amelioration culminating with
Dacrydium cuppressinum-dominant lowland forest at western sites as early as
11.9 ka, indicative of the start of the Holocene. A disturbance in forest
development occurs between 13.4-11.9 ka in one record and may be indicative of
a minor cooling within the timeframe of a late glacial climate reversal recognised in
the NZI-CES.
Overall the project results (timing and pattern of climate change) broadly align with
the NZ-I CES. However, there are some disparities, in particular during the LGCP,
which this study suggests began at least 3-4 ka earlier than concluded in the NZ-I
CES. The NZ-I CES oversimplifies the complexity of the LGCP which contains
evidence of significant climate variability that may be important for an
understanding of the possible forcing factors on climate change. The chronology
derived from the current study supports recent evidence that points towards a
younger, refined age of 25.4 ka for the Kawakawa/Oruanui Tephra, a key
chronostratigraphic marker for the LGCP. Pollen-climate models and
Environmental Lapse Rates were used to quantify changes in mean annual
temperatures with sometimes conflicting results. This research reveals some
limitations of the current New Zealand pollen-climate transfer function when
applied to reconstruction of cold climate periods in particular. These include a lack
of limitations with modern analogues and a number of wide-ranging pollen taxa
that encompass a broad climate envelope. The current research also highlights
the potential of regional climate regimes and spatial differences in vegetation and
inferred climate reconstructions. These differences pose a major limitation for a
New Zealand-wide composite. While the NZ-I CES provides a valuable framework
of climate change during a period of large climate variability, results of this study
highlight aspects that need further consideration and revision
Paleo-environmental reconstruction of a Late Quaternary organic-rich section preserved near Ohakune, central North Island, New Zealand
No full textA 6m thick section of organic-rich sediment, exposed at Karioi, near Ohakune, central North Island (672m above sea level), presents an opportunity to form a detailed palynological record of Late Quaternary vegetation and climate change. The organic-rich sequence at Karioi lies beneath a 3.29m thick cover-bed sequence that contains towards its base the c. 25.4 ka cal BP Kawakawa/Oruanui Tephra, a key chronostratigraphic marker for the Last Glacial Maximum (LGM) throughout New Zealand. A previous palynological investigation of the underlying organic sediments suggested they extended back from the LGM (Marine isotope stage 2) to the previous interglacial (MIS 5). Such apparently continuous terrestrial records spanning this age range and located at this altitude are rare.
A key feature of the Karioi organic sequence is the occurrence of numerous millimetre- to decimetre- thick tephra, derived from a variety of North Island eruptive sources. The possibility that volcanic processes have influenced vegetation change makes climate inferences at this important site potentially problematic. In this new study of the Karioi section, centimetre-scale palynological and diatom sampling conducted above and below three selected tephra (here named ‘Big Lower Lapilli’, ’Unknown’ tephra, and ‘Little’ tephra) at Karioi, were used to assess the influence of these volcanic events on the vegetation and local hydrology. Loss-on-ignition and magnetic susceptibility were used, alongside pollen and diatom analysis, to infer changes in local hydrology and depositional processes in relation to environmental stability. Together, these analyses helped determine the volcanic impacts on vegetation assemblages gained from the pollen record at the site and allowed these to be disassociated from larger scale climate influences of interest.
The results of this study indicate a discernible volcanic impact on vegetation and hydrology following just one of the three volcanic events targeted in the record. High-resolution (0.5cm) pollen analysis above and below the largest of the three tephra layers, the 22cm thick ‘Big Lower Lapilli’ showed a notable change in vegetation assemblage immediately following tephra deposition. The most significant of these changes was the marked increase in herbs. This was an unexpected result thought to be due to the proximity of the site to sub-alpine and alpine herbaceous communities, which in turn were closer to the source of volcanism than other vegetation communities depicted in the pollen record. The changes to the pollen spectra are estimated to have taken 300 years to return to pre-eruption assemblages.
Magnetic susceptibility and loss-on-ignition results further add to this research by indicating the comparative stability of the depositional environment around the time of deposition of the ‘Big Lower Lapilli’. Statistical analysis further identified a change in vegetation communities associated with tephra deposition, coinciding with an increase in diatom species abundance, which signified an increase in water volume and depth at the site. This was most clearly seen by the marked increase in Aulacoseira ambigua, which is almost exclusively found in water bodies of at least 2 metres depth.
These results have major implications for pollen-based climate reconstructions from sequences with interbedded tephra layers. First, such investigations should include fine resolution analyses around prominent tephra layers to test for possible volcanic disturbance that may be a confounding factor in any paleoclimatic reconstructions applied. In this study, for example, vegetation assemblages may have taken up to 300 years to return to pre-eruption levels, but this recovery phase was well within the c. 1000 year inter-sample period of the original coarse (10cm) resolution record. Without the fine resolution study conducted here, the decline of shrubs and increase in grasses, with no obvious changes to trees following deposition of the ‘Big Lower Lapilli’ could have been inferred as a short-term cooling interval. Beyond this restricted zone of volcanic disturbance, greater confidence in the paleoclimatic interpretation of the Karioi pollen record has been achieved as a result of this finer resolution ‘test’ for volcanic disturbance. Second, the volcanic disturbance indicated following the ‘big lower lapilli’ has shed light on pollen taphonomic sources and pathways at this site and in turn, on spatial patterns of vegetation communities. In this case, the increase in tree pollen relative to non-arboreal pollen is interpreted as originating from more distant forest stands that have been comparatively less affected by the deposition of tephra than locally growing vegetation
Climate change since the Last Interglacial in northern New Zealand inferred from pollen and chironomid records of the Auckland Maars
No full textIn light of contemporary climate change it is more important than ever to understand past shifts in climate, especially past warm phases, and their effects on ecosystems and societies. From compilations of global climate reconstructions, several periods have been identified that might have been warmer than today, the two most recent of which are the Holocene Thermal Maximum (~11 – 5 kyr BP) and the Last Interglacial (~129 – 116 kyr BP). However, spatio-temporal complexities are typically smoothed out in global climate reconstructions and we do not have a good understanding of the regional differences in past climate. The southern mid-latitudes especially are underrepresented in palaeoclimate research.
For this thesis I analyse the sediments from two maars within the Auckland Volcanic Field: Orakei Basin, which erupted ~126.0 kyr BP and accumulated sediments until ~9 – 8.5 kyr BP; and Lake Pupuke, which still contains a lake today and therefore covers the Holocene. Quantitative climate reconstructions are necessary to put the Orakei Basin and Lake Pupuke records in a broad context and to enable comparisons of past and future climates. For this study I focus on biological proxies preserved by lake sediments, namely pollen, which primarily responds to mean annual air temperatures (MAAT), and chironomids, a surrogate for summer air temperatures (SmT). Together, MAAT and SmT reconstructions from the same site can provide insight into changing seasonality over time, an underexplored dimension of proxy-based reconstructions. The chironomid record covers just the last ~14 cal kyr BP however, because of low head capsule abundances in older sediment sections.
The Orakei Basin pollen record and associated MAAT reconstruction cover ~85 to 9 cal kyr BP and show five distinct phases comparable to Marine Isotope Stages (MIS) 5 to 1. This association is confirmed by the preliminary tephrochronology of the core. The broad similarity of the Orakei MAAT trend to the MIS and other records from New Zealand implies all were driven by northern high-latitude summer insolation, consistent with the Milankovitch orbital forcing hypothesis. Several patterns superimposed on the general trend stand out: first, MIS 4 is a brief cool period, which is inconsistent with the observation that glacier advances equivalent to those of the late last glacial maximum occurred ~65 kyr BP in the Southern Alps, possibly due to the seasonal distribution of energy from solar insolation. Second, MIS 3 displays an earlier warm phase followed by a progressive cooling trend which might be correlated to decreasing local summer insolation intensity. Third, glacial conditions of MIS 2 appear consistent with the early onset of the last glacial maximum in the southern mid latitudes, which was likely driven by regional insolation intensity.
The Lake Pupuke pollen and chironomid records, covering the last ~14 cal kyr BP, show no evidence of a past warm period equivalent to the Holocene Thermal Maximum. MAAT is stable throughout the Holocene, whereas SmT increases between 10 and 3 cal kyr BP. The latter shows a strong relationship with integrated local summer insolation. The temperature reconstructions lead to the conclusion, first, that seasonality was low during the Early Holocene (12 to 9.3 cal kyr BP), and second, that during mid-to-late Holocene (after ~7 cal kyr BP) summers were hot and dry, allowing the tall conifer kauri to expand throughout northern New Zealand.
The Lake Pupuke chironomid-SmT reconstruction highlighted an issue with the transfer function model, namely, that it was not able to reconstruct values close to modern day (18.9°C). Therefore, I explore an extended training set which encompasses a longer temperature gradient. New models are fitted using both traditional techniques and modern machine learning methods. The new model improves the SmT reconstruction from Lake Pupuke, in the sense that reconstructed temperatures now reach modern day values. However, the SmT trend is the same as the original trend, substantiating the previously drawn conclusions.
During the course of this research, I discovered that density separation during pollen preparation can lead to varying relative abundances, depending on the specific gravity used. After some experimentation I found that using a low specific gravity (2.0; recommended value in the literature) can result in the overrepresentation of buoyant pollen grains, leading to erroneous interpretations.
Together, these results point out the importance of considering regional-to-local drivers of climate changes superimposed on global reconstructions. Multi-proxy records can help disentangle the different aspects of the climate system, where especially chironomids can be helpful to elucidate the role of SmT and local summer insolation. Finally, this thesis shows the importance of questioning the appropriateness of conventional methodologies and where possible, addressing their limitations
Late Holocene Sediment Deposition in Lake Wairarapa
No full textLake Wairarapa is a highly modified lacustrine system at the southern end of the North Island, New Zealand. Not only is it situated in a region that is affected by catchment altering natural phenomena such as earthquakes, storms and fire, but both the catchment and hydrology of the lake have also been significantly altered by humans. Polynesian settlers arrived in the area approximately 700BP and proceeded to deforest the lowlands. European settlers began arriving from 1844AD onwards, completing deforestation of the lowlands and Eastern Uplands. In 1964 the Lower Wairarapa Valley Development Scheme was commissioned in an effort to alleviate flooding. This scheme significantly altered the hydrological regime of the lake.
Interest in the condition of the lake and associated wetlands, and the realization that it has important recreational, cultural and ecological value, began to develop in the 1990's. This has led to a desire to see the lake restored to a more natural condition while still maintaining its flood protection capabilities. However, the lake has only been monitored over the last several decades. Any evidence of the lakes condition prior to this time is anecdotal and little is known of its natural tendencies and functions.
This research has investigated and quantified morphological changes to Lake Wairarapa at the decadal and millenial scale using a combination of aerial photograph analysis, bathymetric survey comparison and lakebed core analysis. Study at these diverse scales has allowed the observed changes to be related to human environmental modification, while also being juxtaposed against natural trajectories of change. It is hoped that this can inform lake management and restoration efforts and provide a benchmark for measuring future changes to the lake, while also addressing wider issues concerning natural versus anthropogenic landscape change at the local and regional scale.
The results of this project suggest that the lake has been steadily infilling over the last 6000BP – particularly along the eastern shore. For the two decades after significant hydrological changes to the lake associated with the Lower Wairarapa Valley Development Scheme, the rate of infilling on the eastern shore increased more than tenfold. However, this was accompanied by deepening in other parts of the lake. Today infilling along the eastern shore appears to have returned to natural rates and overall the lake in 2010 is only slightly smaller in volume than in 1975.
Longer term anthropogenic influence on the lake and catchment was also evident. In particular Polynesian settlement and subsequent deforestation by fire was apparent in the lakebed cores. This result not only addresses the immediate issue of anthropogenic influence on this particular lacustrine system, but also informs the debate surrounding the dating of Polynesian arrival in New Zealand
Utility of the MBT/CBT paleotemperature proxy in lake sediments: Spatial variation in bacteria and bacterial lipid distribution in two New Zealand lake catchments
No full textBranched glycerol dialkyl glycerol tetraethers (GDGTs), produced by unidentified bacteria, have been found ubiquitously in terrestrial and marine environments. The methylation and cyclisation of branched GDGTs is known to change in soils due to mean annual air temperature and pH, respectively. The identification of branched GDGTs produced within the water column and sediments of lakes indicates strong potential for the development of a temperature proxy for lake environments. In order to help develop the applicability of using branched bacterial GDGT lipids as a temperature proxy in lacustrine environments, this research set out to determine the distribution and provenance of bacterial communities and their corresponding GDGT lipids present in lake sediments in two small New Zealand lakes, the Karori Upper Dam and Lake Pounui. The Karori Upper Dam is a small lake, directly fed by two tributaries. Lake Pounui, in comparison, is much larger and fed by tributaries which are buffered by swamps.
Water and sediment samples from Lake Pounui and its catchment indicate a predominantly autochthonous production of branched GDGTs. However, the lake calibrated MBT/CBT paleotemperature proxy is not applicable to sites similar to that of the Karori Upper Dam which have a strong terrestrial branched GDGT signature. This research concluded that it can be expected that a terrestrial GDGT signature of some extent will be present in all lacustrine sites; however, only some sites will display a strong authochthonous lacustrine GDGT signal suitable for the application of the MBT/CBT paleotemperature proxy. Through the use of ARISA DNA analysis this research identified bacterial species which statistically explain a significant portion of variance in branched GDGT abundances. Based on the seasonal fluctuations of measured environmental controls it can be assumed that species abundance will also fluctuate. Future work will need to be undertaken in order to further understand this relationship as the sample size for this research was too small to determine the seasonal pattern of these bacteria
Gold Mining and Estuarine Evolution: A Study of the Accelerated Sedimentation of Parapara Inlet, Golden Bay, New Zealand
No full textEstuaries are depositional environments formed within drowned river embayments which receive sediment from both marine and terrestrial sources. In many cases a beach-barrier sequence forms subaerially at the mouth of the flooded embayment and the area behind it is termed a barrier estuary. Such estuary types are found around the New Zealand coast especially in areas of relative tectonic stability and their sediments are often used to reconstruct Holocene sea level. Infill of these estuaries is initially dominated by marine flood tide delta sediments, with later infill occurring through fluvial processes. The final stages of infill within these estuaries is poorly understood. Parapara Inlet in Golden Bay, New Zealand, is a Holocene barrier estuary influenced by hydraulic sluice mining within its river catchment. A study of Parapara Inlet was undertaken to discover how human disturbance within a river catchment can affect the evolution of a barrier estuary, by comparing previous models of barrier estuary evolution to the stratigraphy record within Parapara Inlet. 18 vibracores were sampled from Parapara Inlet in November 2009. Radiocarbon dating (AMS) within these cores provided a maximum age of 7090-6910 Cal BP. Deposition within the estuary has occurred in three stages; the first in Pre-Holocene marsh or lake environments; the second after inundation 6500-7500 years Cal BP, as fluvial sediments dominate the centre of the estuary; and thirdly in a series of quartz dominated gravels and sands within 1m of the surface. These units vary from the traditional models of evolution as the topography of the estuary has influenced the extent of deposition within the central mud basin. Mining sediment forced Parapara Inlet into a late stage of evolution, however the amount of sediment provided through sluice mining was not large enough to force the estuary into a supratidal stage
Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki
No full textA multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology.
Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context.
Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon.
Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness.
The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time
Stratigraphy, age and correlation of two widespread Late Holocene tephras preserved within Lake Kutubu, Southern Highlands Province, Papua New Guinea
No full textSediment cores were retrieved from Lake Kutubu, the largest upland lake in Papua New Guinea, to assess palaeoenvironmental baselines. Two prominent tephra layers were encountered within the cores. Using a combination of core stratigraphy, sediment properties and geochemical characterization (electron microprobe and laser ablation inductively coupled-plasma mass spectrometry techniques) we were able to correlate these tephras with Tibito and Olgaboli tephras, both previously described at adjacent distal localities. Glass shard compositional data of Tibito tephra from Lake Kutubu, Kuk swamp and from proximal volcaniclastic successions from Long Island are indistinguishable and this similarity strongly supports Long Island as the eruptive source. For Olgaboli tephra, the location of its eruptive source is less certain but the glass shard compositional data indicate a Karkar Island source. The occurrence of Tibito and Olgaboli tephras in Lake Kubutu sediments extends their known distributions further south-west into the southern Highlands region and affirms their importance as inter-regional stratigraphic markers, of late Holocene age, that have considerable potential for use in future palaeoenvironmental, archaeological and volcanic hazard and/or impact studies. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd
- …
