Integrated age modelling of numerical, correlative and relative dating of a long lake sediment sequence from Orakei maar palaeolake, Auckland, New Zealand
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Date
2019-04-11
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Copernicus GmbH
Abstract
Accurate and precise chronologies are fundamental for successful Quaternary palaeo-climate/environment
reconstruction and correlation with global climatic events. Aside from varved lake sequences, chronologies for
sediment archives typically depend on age models developed from a limited number of dated horizons, often with
large associated errors, age reversals, or minimum/maximum age constraints. Whilst the approach to generating
chronologies for sediment cores has moved on from linear interpolation to considering age uncertainties and
developing more nuanced accumulation models, these age models rarely reach the resolution and precision desired
for millennial-scale palaeo-climatic correlations, particularly beyond the limits of the more precise radiocarbon
method. Bayesian modelling offers the opportunity to optimise age models by combining all available information
on the depositional history of the basin.
Here we address this issue for the Orakei maar palaeolake sequence from Auckland, New Zealand. The Orakei
maar sequence offers a high-resolution and continuous record of climatic variations spanning much of the last
glacial cycle and is one of the few from the southern hemisphere mid-latitudes. The Orakei sequence spans ca.
120 to 10 ky; our chronology is derived from tephrochronology, radiocarbon dating, post-IR IRSL luminescence
dating, relative palaeomagnetic intensity changes and meteoric Beryllium-10 flux. Prior to 40 ka, our age model
relies on comparison with the global PISO-1500 palaeointensity stack and 10Be-flux. We generate our age
model for the time interval ca. 50 to 10 ky using Bacon (rBacon in R), using non-normal error distribution
of un-calibrated ages when necessary, facies-dependent variable mean accumulation rates and accounting for
thick horizons of instantaneous deposition (i.e. tephra and mass movement deposits). This approach allows us to
generate a high-resolution age model suitable for correlation of millennial-scale oscillations in our record, based
on environmental magnetism and meteoric 10Be flux, with global records of past climate such as polar ice core,
tropical lake and speleothem archives.
© Author(s) 2018. CC Attribution 4.0 license.
Description
Keywords
Simulation, Caves, Lakes, New Zealand, Climates, Environment, Sediments, Glaciers, Carbon 14, Beryllium 10
Citation
Peti, L., Augustinus, P. C., Fink, D., Fujioka, T., Mifsud, C., Nilsson, A., Muscheler, R., Fitzsimmons, K. E., & Hopkins, J. L. (2019). Integrated age modelling of numerical, correlative and relative dating of a long lake sediment sequence from Orakei maar palaeolake, Auckland, New Zealand. Paper presented to the EGU General Assembly 2019, Vienna, Austria, 7-12 April 2019. In Geophysical Research Abstracts, Vol. 21, EGU2019-274. Retrieved from: https://meetingorganizer.copernicus.org/EGU2019/EGU2019-274.pdf