scholarly journals Development of a multi-method chronology spanning the Last Glacial Interval from Orakei maar lake, Auckland, New Zealand

Geochronology ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 367-410
Author(s):  
Leonie Peti ◽  
Kathryn E. Fitzsimmons ◽  
Jenni L. Hopkins ◽  
Andreas Nilsson ◽  
Toshiyuki Fujioka ◽  
...  
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Large Scale ◽  
Volcanic Eruptions ◽  
Climate System ◽  
Luminescence Dating ◽  
Reference Curve ◽  
Auckland Volcanic Field ◽  
Last Glacial ◽  
Maar Lake

Abstract. Northern New Zealand is an important location for understanding Last Glacial Interval (LGI) palaeoclimate dynamics, since it is influenced by both tropical and polar climate systems which have varied in relative strength and timing. Sediments from the Auckland Volcanic Field maar lakes preserve records of such large-scale climatic influences on regional palaeo-environment changes, as well as past volcanic eruptions. The sediment sequence infilling Orakei maar lake is continuous, laminated, and rapidly deposited, and it provides a high-resolution (sedimentation rate above ∼ 1 m kyr−1) archive from which to investigate the dynamic nature of the northern New Zealand climate system over the LGI. Here we present the chronological framework for the Orakei maar sediment sequence. Our chronology was developed using Bayesian age modelling of combined radiocarbon ages, tephrochronology of known-age rhyolitic tephra marker layers, 40Ar∕39Ar-dated eruption age of a local basaltic volcano, luminescence dating (using post-infrared–infrared stimulated luminescence, or pIR-IRSL), and the timing of the Laschamp palaeomagnetic excursion. We have integrated our absolute chronology with tuning of the relative palaeo-intensity record of the Earth's magnetic field to a global reference curve (PISO-1500). The maar-forming phreatomagmatic eruption of the Orakei maar is now dated to > 132 305 years (95 % confidence range: 131 430 to 133 180 years). Our new chronology facilitates high-resolution palaeo-environmental reconstruction for northern New Zealand spanning the last ca. 130 000 years for the first time as most NZ records that span all or parts of the LGI are fragmentary, low-resolution, and poorly dated. Providing this chronological framework for LGI climate events inferred from the Orakei sequence is of paramount importance in the context of identification of leads and lags in different components of the Southern Hemisphere climate system as well as identification of Northern Hemisphere climate signals.

scholarly journals Development of a multi-method chronology spanning the Last Glacial Interval from Orakei maar lake, Auckland, New Zealand

2020 ◽  
Author(s):  
Leonie Peti ◽  
Kathryn E. Fitzsimmons ◽  
Jenni L. Hopkins ◽  
Andreas Nilsson ◽  
Toshiyuki Fujioka ◽  
...  
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Volcanic Eruptions ◽  
Climate System ◽  
Luminescence Dating ◽  
Reference Curve ◽  
Paleoenvironmental Reconstruction ◽  
Last Glacial ◽  
Relative Paleointensity ◽  
Maar Lake

Abstract. Northern New Zealand is an important site for understanding Last Glacial Interval (LGI) paleoclimate dynamics, since it is influenced by both tropical and polar climate systems which have varied in relative strength and timing of associated changes. The Auckland Volcanic Field maar lakes preserve these climatic influences on the regional paleoenvironment, as well as past volcanic eruptions, in their sedimentary infill. The sediment sequence infilling Orakei maar lake is continuous, laminated, high-resolution and provides a robust archive from which to investigate the dynamic nature of the northern New Zealand climate system over the LGI. Here we present the chronological framework for the Orakei maar sediment sequence. Our chronology was developed combining Bayesian age modelling of combined radiocarbon ages, tephrochronology of known-age rhyolitic tephra marker layers, 40Ar/39Ar-dated eruption age of a local basaltic volcano, luminescence dating (using post infrared-infrared stimulated luminescence, or pIR-IRSL), and the timing of the Laschamp paleomagnetic excursion. We also investigated the application of meteoric (cosmogenic) Beryllium-10 variability to improve the age-depth model by complementing relative paleointensity measurements. However, the results were apparently influenced by some unaccounted catchment process and unable to reach satisfactory interpretation, apart from confirming the presence of the Laschamp excursion, and therefore the 10Be data are not used in the production of the final age model. We have integrated our absolute chronology with tuning of the relative paleointensity record of the Earth’s magnetic field to a global reference curve (PISO-1500). The maar-forming phreatomagmatic eruption of the Orakei maar is now dated to > 130,120 yr (95 % confidence range 128,665 to 131,560 yr). Our new chronology facilitates high-resolution paleoenvironmental reconstruction for northern New Zealand spanning the last ca. 130,000 years for the first time as most NZ records that spall all or parts of the LGI are fragmentary, low-resolution and poorly dated. Providing this chronological framework for LGI climate events inferred from the Orakei sequence is of paramount importance in the context of identification of leads and lags in different components of the Southern Hemisphere climate system as well as identification of Northern Hemisphere climate signals.

scholarly journals Composite development and stratigraphy of the Onepoto maar lake sediment sequence (Auckland Volcanic Field, New Zealand)

2021 ◽  
Vol 29 ◽  
pp. 19-37
Author(s):  
Benjamin Läuchli ◽  
Paul Christian Augustinus ◽  
Leonie Peti ◽  
Jenni Louise Hopkins
Keyword(s):  
New Zealand ◽  
Lake Sediment ◽  
Volcanic Field ◽  
Tuff Ring ◽  
Auckland Volcanic Field ◽  
14C Dating ◽  
Quaternary Climate ◽  
Laminated Sediment ◽  
Continuous Record ◽  
Maar Lake

Abstract. The accurate and precise reconstruction of Quaternary climate as well as the events that punctuate it is an important driver of the study of lake sediment archives. However, until recently lake sediment-based palaeoclimate reconstructions have largely concentrated on Northern Hemisphere lake sequences due to a scarcity of continuous and high-resolution lake sediment sequences from the Southern Hemisphere, especially from the southern mid-latitudes. In this context, the deep maar lakes of the Auckland Volcanic Field of northern New Zealand are significant as several contain continuous and well-laminated sediment sequences. Onepoto Basin potentially contains the longest temporal lake sediment record from the Auckland Volcanic Field (AVF), spanning from Marine Isotope Stage 6e (MIS 6e) to the early Holocene when lacustrine sedimentation was terminated by marine breach of the south-western crater tuff ring associated with post-glacial sea-level rise. The Onepoto record consists of two new, overlapping cores spanning ca. 73 m combined with archive material in a complete composite stratigraphy. Tephrochronology and 14C dating provide the fundamental chronological framework for the core, with magnetic relative palaeo-intensity variability downcore, and meteoric 10Be influx into the palaeolake to refine the chronology. The µ-XRF (micro X-ray fluorescence) downcore variability for the entirety of the lake sediment sequence has been established with measurement of a range of proxies for climate currently underway. This work will produce the first continuous record of the last 200 kyr of palaeoclimate from northern New Zealand to date.

scholarly journals High-Resolution Vegetation Mapping Using eXtreme Gradient Boosting Based on Extensive Features

2019 ◽  
Vol 11 (12) ◽  
pp. 1505 ◽  
Author(s):  
Heng Zhang ◽  
Anwar Eziz ◽  
Jian Xiao ◽  
Shengli Tao ◽  
Shaopeng Wang ◽  
...  
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Large Scale ◽  
Field Survey ◽  
Terrestrial Ecosystems ◽  
Google Earth ◽  
Gradient Boosting ◽  
Global Changes ◽  
Vegetation Map ◽  
Extreme Gradient Boosting

Accurate mapping of vegetation is a premise for conserving, managing, and sustainably using vegetation resources, especially in conditions of intensive human activities and accelerating global changes. However, it is still challenging to produce high-resolution multiclass vegetation map in high accuracy, due to the incapacity of traditional mapping techniques in distinguishing mosaic vegetation classes with subtle differences and the paucity of fieldwork data. This study created a workflow by adopting a promising classifier, extreme gradient boosting (XGBoost), to produce accurate vegetation maps of two strikingly different cases (the Dzungarian Basin in China and New Zealand) based on extensive features and abundant vegetation data. For the Dzungarian Basin, a vegetation map with seven vegetation types, 17 subtypes, and 43 associations was produced with an overall accuracy of 0.907, 0.801, and 0.748, respectively. For New Zealand, a map of 10 habitats and a map of 41 vegetation classes were produced with 0.946, and 0.703 overall accuracy, respectively. The workflow incorporating simplified field survey procedures outperformed conventional field survey and remote sensing based methods in terms of accuracy and efficiency. In addition, it opens a possibility of building large-scale, high-resolution, and timely vegetation monitoring platforms for most terrestrial ecosystems worldwide with the aid of Google Earth Engine and citizen science programs.

scholarly journals Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere

2006 ◽  
Vol 2 (1) ◽  
pp. 11-19 ◽  
Author(s):  
H. Rother ◽  
J. Shulmeister
Keyword(s):  
New Zealand ◽  
Southern Hemisphere ◽  
Large Scale ◽  
Late Quaternary ◽  
Synoptic Climatology ◽  
Balance Model ◽  
Last Glacial ◽  
Regional Flow ◽  
Quaternary Glaciations ◽  
The Last Glacial

Abstract. The relative timing of late Quaternary glacial advances in mid-latitude (40-55° S) mountain belts of the Southern Hemisphere (SH) has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand (NZ) and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH) forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glaciation in the temperate and hyperhumid Southern Alps of New Zealand can be generated with moderate cooling. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1-4°C). Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM) and the Last Glacial Interglacial Transition (LGIT) occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal).

High-resolution Geomagnetic Field Records Decipher the Possible Precession links since about 340-kyr in a maar lake sediment sequence in tropical Asia

2020 ◽  
Author(s):  
Xiaoqiang Yang ◽  
Cong Chen ◽  
Zhuo Zheng
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Geomagnetic Field ◽  
Southern China ◽  
Singular Spectrum Analysis ◽  
Luminescence Dating ◽  
Large Spatial Scale ◽  
The Earth ◽  
Earth Magnetic Field ◽  
Maar Lake

<p>A series of paleomagnetic works relying on the ocean sediments present some significant astronomic periods, such as a 100 kyr quasi-period and 41 kyr obliquity signal. These studies provide the new insights unscrambling what and how the earth magnetic field changed in despite of the ongoing debating. Numerical studies of recent years also reveal the possibility of the precession drive the dynamos and influence the magnetic field. However, the less of reliable high-resolution paleomagnetic records besides of relative paleointensity reduce its credibility. Here, we present some detailed rock magnetic and paleomagnetic studies on the continuous 40-m-thick sediments in two parallel cores retrieved from Tianyang Maar lake, southern China. The new results would contribute to discuss the correlation of paleomagnetic field with the astronomical factors.</p><p>Tianyang Maar lake  is located in the southern part of the Leizhou Peninsula.  The maar lake has a surface area of ~ 7.3 km<sup>2</sup> surrounded by a 40 - 60 m high crater rim composed of basaltic breccia and tuff . Two new parallel cores, TY08 and TY15 (~ 10 m apart), were extracted from center of the crater in 2008 and 2015, respectively, using a rotary borer consisting of a stainless steel outer tube and a plastic inner tube to minimize sediment disturbances and contamination. The sediments of two cores can divided into three zones: about upper 15.59 m was composed of varying colors clay and the middle part (15.59-21.94 m), was dominated by the grey and greyish-brown fine to coarse sand with occasional gravels, embedded a thick grey clay layer; the lower part (21.94-40.0 m) shown as the dark grey and black organic-rich clay.</p><p>The paleomagnetic results show that the natural remanent magnetization (NRM) of the sediments is mainly contributed by magnetically soft minerals, and the sediments have fairly documented geomagnetic field variations. A chronology is constructed using multiple methods, including radiocarbon dating, optically stimulated luminescence dating and terrestrial-marine pollen correlation. The 340-kyr paleomagnetic inclination record displays patterns similar to those seen in regional records over a large spatial scale (> 3000 km), implying that these records may reflect large-scale core dynamics on timescales of 10<sup>4 </sup>- 10<sup>5</sup> years in this low-latitude region. The Tianyang inclination record exhibits a negligible inclination anomaly (∆I = -0.08°) and features six anomalous inclination events, which are assigned to the Laschamp, Blake, Fram Strait II/6α, Iceland Basin, Mamaku and 9α excursions respectively. The spectral and singular spectrum analysis (SSA) exhibit that the inclination does not show the significant signal of 100-kyr periodicity, however, the closed precession period is obvious in the third components of inclination (PC3). PC3 component shows nearly synchronous variations with the precession parameter while the opposite correlation appeared under the condition of eccentricity minima strong. This corresponding pattern hint us that astronomical parameters have the essential influence to the earth magnetic field, however, the different moving may forc or constrain the earth magnetic behavior.</p>

scholarly journals Synoptic climate change as a driver of late Quaternary glaciations in the mid-latitudes of the Southern Hemisphere

2005 ◽  
Vol 1 (3) ◽  
pp. 231-253 ◽  
Author(s):  
H. Rother ◽  
J. Shulmeister
Keyword(s):  
New Zealand ◽  
Southern Hemisphere ◽  
Large Scale ◽  
Late Quaternary ◽  
Synoptic Climatology ◽  
Balance Model ◽  
Last Glacial ◽  
Regional Flow ◽  
Quaternary Glaciations ◽  
The Last Glacial

Abstract. The relative timing of late Quaternary glacial advances in mid-latitude (40–55° S) mountain belts of the Southern Hemisphere (SH) has become a critical focus in the debate on global climate teleconnections. On the basis of glacial data from New Zealand and southern South America it has been argued that interhemispheric synchrony or asynchrony of Quaternary glacial events is due to Northern Hemisphere (NH) forcing of SH climate through either the ocean or atmosphere systems. Here we present a glacial snow-mass balance model that demonstrates that large scale glacial advances in the temperate and hyperhumid Southern Alps of New Zealand can be generated with very little thermal forcing. This is because the rapid conversion of precipitation from rainfall to snowfall drives massive ice accumulation at small thermal changes (1–4°C). Our model is consistent with recent paleo-environmental reconstructions showing that glacial advances in New Zealand during the Last Glacial Maximum (LGM) and the Last Glacial Interglacial Transition (LGIT) occurred under very moderate cooling. We suggest that such moderate cooling could be generated by changes in synoptic climatology, specifically through enhanced regional flow of moist westerly air masses. Our results imply that NH climate forcing may not have been the exclusive driver of Quaternary glaciations in New Zealand and that synoptic style climate variations are a better explanation for at least some Late Quaternary glacial events, in particular during the LGIT (e.g. Younger Dryas and/or Antarctic Cold Reversal).

scholarly journals Tree-Ring Based Reconstructions of Paleo-Precipitation Regimes in the Eastern Yellowstone Region

2000 ◽  
Vol 24 ◽  
pp. 144-148
Author(s):  
S. Gray ◽  
S. Jackson ◽  
K. Taylor ◽  
C. Palmer ◽  
C. Fastie
Keyword(s):  
High Resolution ◽  
Solar Radiation ◽  
Tree Ring ◽  
General Circulation ◽  
Large Scale ◽  
General Circulation Models ◽  
Climate Variation ◽  
Climate System ◽  
Precipitation Regimes ◽  
Instrumental Records

There are few other regions where the influence of climate on basic ecosystem attributes has been as well documented as the Greater Yellowstone Ecosystem (GYE). Research has shown that elk, bison, and grizzly bear populations in the GYE are tightly linked to annual climate variation (Meagher 1976, Picton 1978). Authors have shown that the distribution of vegetation types in Grand Teton and Yellowstone National Parks is influenced by the seasonality of precipitation (Despain 1987, 1990). Natural disturbances, especially fires and insect outbreaks, are also known to coincide with specific climate scenarios in this region (Knight 1987, Balling et al. 1992). Therefore, understanding how climate can vary over time is essential for the proper management of these areas (Luckman 1996). Modem instrumental records have contributed greatly to our understanding of the current GYE climate system. In particular, work by Mock (1996) and Bartlein et al. (1997) has demonstrated how local manifestations of large-scale circulation patterns produce distinct climates within the GYE. In addition, studies using modem climate records and General Circulation Models by Balling et al. (1992) and Bartlein et al. (1997) have identified trends toward increasing aridity in the GYE and the potential for these trends to continue well into the future. Late Pleistocene and Holocene (18-1 kya) climate in the GYE is known mainly from lake­sediment cores. Work by Whitlock (1993), Whitlock and Bartlein (1993), and Thompson et al. (1993) indicates that after deglaciation, increased solar radiation during summer months led to a highly seasonal climate regime. As levels of solar radiation changed through the Holocene, GYE climate became increasingly more like today until the modem regime became established around 1500-1600 AD (Whitlock 1993, Elias 1997). While existing modem and paleoecological studies reveal important aspects of the GYE climate system, there is a distinct lack of high-resolution data for most of the last millennium. Lake sediments only record climate variation at a resolution of hundreds to thousands of years, and instrumental records do not exist before the 1890s. Dendroclimatology, the study of climate using patterns of tree-ring growth (Fritts 1976) is particularly well suited to fill this gap in our knowledge of GYE climate. Tree-rings have been used successfully for climate reconstructions worldwide, offer records spanning decades to millennia, and can provide annual resolution. Therefore, we are developing a network of tree-ring sites in the western Absaroka Mountains and eastern Bighorn Basin to fill important spatial (areas east of Yellowstone NP) and temporal (high resolution for the past 700-1,000+year) gaps in our knowledge of GYE climate.

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