Integrating chronological uncertainties for annually laminated lake sediments using layer counting, independent chronologies and Bayesian age modelling (Lake Ohau, South Island, New Zealand)

Vandergoes, Marcus J.; Howarth, Jamie; Dunbar, Gavin B.; Turnbull, J. C.; Roop, H. A.; Levy, R. H.; Li, Xun; Prior, Christine; Norris, Margaret; Keller, Elizabeth D.; Baisden, W. T.; Ditchburn, R.G.; Fitzsimons, Sean J.; Ramsey, Christopher Bronk

doi:10.1016/j.quascirev.2018.03.015

Cited by 14 publications

(14 citation statements)

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“…The age models for both cores provides for annually resolvable accumulation. Age model development included (1) generating a single density-depth profile from CT scans of the core, (2) normalizing the density-depth profile to remove the effects of compaction, and (3) picking annual layers based on the density amplitude, spacing, and gradient while incorporating age independent age constraints, including 137 Cs profiles, biostratigraphic horizons and 14 C ages (Vandergoes et al, 2018). Further details on the age model generation are included in Supplemental Text.…”

Section: Lake Ohau Sediment Cores and Age Modelsmentioning

confidence: 99%

Toward a novel multi-century archive of tree mast using pollen from lake sediments

et al. 2022

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Mast seeding – the pronounced inter-annual variability and synchrony in seed production – can have profound local ecological impacts. We explore the potential for generating long (centuries to millennia) proxy records of tree mast seeding, from pollen deposited in lake sediments. This proxy record uses pollen recovered from annually-banded (varved) sediments from a core collected from Lake Ohau, South Island, New Zealand to reconstruct masting events for two genera of Southern Beech, Fuscospora spp. and Lophozonia spp. We find average mast frequencies inferred from Fuscospora pollen from a 43-year sediment core collected from Lake Ohau comparable to seed fall expected for the catchment using a differential-temperature (ΔT) statistical model for the period 1974–2016. In contrast, Lophozonia pollen mast frequency in the 1974–2016 timeseries was consistently lower than that predicted by the ΔT model, although the patterns of variability were broadly similar. We explore this approach in a second 32-year pollen timeseries from Lake Ohau, spanning the pre-instrumental period 1833–1864. During this interval, average air temperature was ~1°C cooler than the late 20th century, and interannual variability of air temperature was subdued, such that mast frequency predicted by the Δ T model is the lowest in 200 years. We find mast frequency in our pollen records reflects this pattern for Fuscospora, with a minima of mast frequency from 1850, compared to the 1974–2016 record, but not for Lophozonia. This paper demonstrates that a centuries-long pollen record from the Lake Ohau sedimentary sequence has the potential to form a valuable proxy for Fuscospora masting that would supplement existing seedfall records. Long records of this type could significantly enhance our understanding of the environmental drivers of mast seeding.

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Section: Lake Ohau Sediment Cores and Age Modelsmentioning

confidence: 99%

Toward a novel multi-century archive of tree mast using pollen from lake sediments

et al. 2022

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“…A) Model based only on radiocarbon dates. B) This parameter-based varve integration method introduced by Vandergoes et al (2018) compares several varve integration techniques for sediments from Lake Ohau (New Zealand) using both OxCal and Bacon. Here, we select the integration approach with Bacon, where the "varve counts function" is the source for the prior-parameter of mean accumulation rate.…”

Section: Bayesian Age-depth Modellingmentioning

confidence: 99%

“…Here we select three different methods to integrate varve and radiometric dating and apply it to the Holzmaar data. We concentrate on approaches using the Bacon package for the R statistical programming software (Blaauw and Christen, 2011), whereas literature also provides comparable methods for alternative Bayesian age-depth modelling software, such as OxCal (Martin-Puertas et al, 2021;Ramsey, 2008;Vandergoes et al, 2018), which was also used to integrate varve counting and radiometric dating for the Holocene sediment record HZM96-4a,4b from Holzmaar (Prasad and Baier, 2014).…”

Section: Introductionmentioning

confidence: 99%

Bayesian age-depth modelling applied to varve and radiometric dating to optimize the transfer of an existing high-resolution chronology to a new composite sediment profile from Holzmaar (West-Eifel Volcanic Field, Germany)

Birlo

Tylmann²,

Zolitschka

2022

Preprint

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Abstract. This study gives an overview of different varve integration methods with Bacon. These techniques will become important for the future as technologies evolve with more sites being revisited for the application of new and high-resolution scanning methods. Thus, the transfer of existing chronologies will become necessary, because the recounting of varves will be too time consuming and expensive to be funded. We introduce new sediment cores from Holzmaar (West-Eifel Volcanic Field, Germany), a volcanic maar lake with a well-studied varved record. Four different age-depth models (A-D) have been calculated for the new composite sediment profile (HZM19) using Bayesian statistics with Bacon. All models incorporate new Pb-210 and Cs-137 dates for the top of the record, the latest calibration curve (IntCal20) for radiocarbon ages as well as the new age estimation for the Laacher See Tephra. Model A is based on previously published radiocarbon measurements only, while Models B-D integrate the previously published varve chronology (VT-99) with different approaches. Model B rests upon radiocarbon data, while parameter settings are obtained from sedimentation rates derived from VT-99. Model C is based on radiocarbon dates and on VT-99 as several normal-distributed tie-points, while Model D is segmented into four sections: Sections 1 and 3 are based on VT-99 only, whereas Sections 2 and 4 rely on Bacon age-depth models including additional information from VT-99. In terms of accuracy, the parameter-based integration Model B shows little improvement over the non-integrated approach, whereas the tie point-based integration Model C reflects the complex accumulation history of Holzmaar much better. Only the segmented and parameter-based age-integration approach of Model D adapts and improves VT-99 by replacing sections of higher counting errors with Bayesian modelling of radiocarbon ages and thus efficiently makes available the best possible and precise age-depth model for HZM19. This approach will value all ongoing and high-resolution investigations for a better understanding of decadal-scale Holocene environmental and climatic variations.

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“…Radiocarbon ( 14 C) dating is widely used to constrain timing of deposition of sediment, peats, swamp material and other terrestrial archives. Applications include paleoclimate reconstructions (Vandergoes et al 2013b(Vandergoes et al , 2018, past earthquake and tsunami events (Clark et al 2015;Howarth et al 2016;Cochran et al 2017) and archaeology (McWethy et al 2010;Maxwell et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Pretreatment of Terrestrial Macrofossils

et al. 2020

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Acid-alkali-acid (AAA) pretreatment is widely used to clean terrestrial plant macrofossil samples for radiocarbon (14C) dating. There is wide variation amongst laboratories in the AAA method details and less rigorous AAA pretreatment is often used on fragile or small samples. Yet there is little evidence as to the efficacy of the different methods and whether the use of less rigorous methods is justified. We investigated four variations of AAA pretreatment: acid only (no alkali wash); room temperature AAA; “standard” AAA at 85°C; and “aggressive” AAA at 85°C with alkali washes repeated until no discoloration was detected. We tested six different terrestrial macrofossils from four different locations and ranging in age from mid-Holocene to the Last Glacial Maximum. Our results demonstrate that while acid only is not always sufficient to remove young material, there is no difference in 14C age of samples pretreated by any of the AAA variants. We also observed mass loss of 85–90% in the standard and aggressive AAA pretreatments, and much more modest mass loss in the room temperature AAA pretreatment. Therefore, we conclude that room temperature AAA pretreatment is optimal to remove contaminating material from fragile terrestrial macrofossils while retaining the majority of the authentic sample material.

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Integrating chronological uncertainties for annually laminated lake sediments using layer counting, independent chronologies and Bayesian age modelling (Lake Ohau, South Island, New Zealand)

Cited by 14 publications

References 64 publications

Toward a novel multi-century archive of tree mast using pollen from lake sediments

Toward a novel multi-century archive of tree mast using pollen from lake sediments

Bayesian age-depth modelling applied to varve and radiometric dating to optimize the transfer of an existing high-resolution chronology to a new composite sediment profile from Holzmaar (West-Eifel Volcanic Field, Germany)

Pretreatment of Terrestrial Macrofossils

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