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Title: Integrated age modelling of numerical, correlative and relative dating of a long lake sediment sequence from Orakei maar paleolake, Auckland, New Zealand
Authors: Peti, L
Augustinus, P
Woodward, C
Nilson, A
Keywords: New Zealand
Age estimation
Quaternary period
Geologic ages
Drill cores
Carbon 14
Issue Date: 10-Dec-2018
Publisher: Australiaian Quaternary Association Inc.
Citation: Peti, L., Augustinus, P., Woodward, C., & Nilson, A. (2018). Integrated age modelling of numerical, correlative and relative dating of a long lake sediment sequence from Orakei maar paleolake, Auckland, New Zealand. Paper presented at the AQUA Biennial, Canberra, 10-14 December 2018.
Abstract: Accurate and precise chronologies are fundamental for any successful Quaternary paleo-climate/- environment reconstruction. Aside from varved lake sequences, all records depend on sediment core age models developed from a limited number of dated horizons, often with large errors. Hence, it is crucial to combine every piece of available information on the depositional history of the basin with modelling tools used for chronology development such as Bacon, a Bayesian age modelling package. Whilst sediment core chronology development has progressed from linear interpolation between dated horizons to considering uncertainties and Bayesian accumulation models, these age models rarely reach the resolution and precision desired for reliable paleo-climatic interpretations, especially in pre-Holocene sequences as errors increase and radiocarbon dating is not suitable anymore. We address this issue here in the context of Orakei maar paleolake sequence, Auckland, New Zealand. This record spans ca. 120 to 10 cal ka BP and is underpinned by tephrochronology, radiocarbon dating and relative changes in paleointensity of the earth magnetic field. Pre-40 cal ka BP, the age model relies on comparison with and correlation to the global PISO-1500 paleointensity stack through dynamic time warping (DTW in R). The chronology for the time interval ca. 50 to 10 cal ka BP has been estimated in Bacon (rBacon in R) with non-normal error distribution of un-calibrated ages, variable mean accumulation rates and accounting for many “slumps” (horizons of instantaneous deposition).The Orakei maar paleo-lake age model is a work in progress but serves as an example for extended age modelling from lake sediment sequences, particularly beyond the radiocarbon age limit. Furthermore, the Orakei maar sequence offers a high-resolution and continuous record of climatic variations that span much of the last glacial cycle and is one of the few from the mid-latitudes of the Southern Hemisphere. The rarity of records of this type makes Orakei maar a crucial record for development of an improved understanding of the global climate system because of its potential to be tied directly to the polar ice core and tropical lake and speleothem records.
Gov't Doc #: 9646
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