Micro-XRF-inferred depositional history of the Orakei maar lake sediment sequence, Auckland, New Zealand

Abstract

Lake sediment records offer insights into past climate and environmental changes. There are, however, few continuous lake sediment records from the Southern Hemisphere mid-latitudes that span the last glacial interval (LGI) and have the requisite chronological control and sampling resolution. Orakei maar paleolake in the Auckland Volcanic Field, New Zealand, is an exception, as it contains a high-resolution record of continuous lacustrine sedimentation from its formative phreatomagmatic eruption ~ 130 ka, until post-glacial sea-level rise breached the crater tuff rim and connected the lake to the sea ~ 9 ka. We used micro-XRF core scanning, dry bulk density, loss-on-ignition and visual facies descriptions to investigate the depositional history of Orakei maar lake as a response to regional and global drivers of climate change, and to erosional events in the lake catchment. The climate history of the lake was divided into six depositional phases: (I) Early warming with frequent in-wash events, followed by climate fluctuations coeval with marine isotope stages (MIS) 5e to mid-5c, (II) Warm, quiescent depositional conditions during mid-MIS 5c to 5a, (III) A colder, windier interval during MIS 4, (IV) Warmer conditions with dominantly autochthonous sedimentation during MIS 3, (V) Cold conditions followed by a slow temperature increase and the onset of sea-level rise during late MIS 2, (VI) Warm conditions that culminated in formation of a peat unit at the top of the Orakei lacustrine sediment sequence, which was terminated by an influx of massive marine muds into the basin at 9.75 ka. Comparison of the inferred climate evolution at Orakei with climate inferences from the global marine benthic MIS record during LGI shows general agreement, though inferred climate changes consistently occur earlier at Orakei than in the MIS. There is also general agreement in temperature changes inferred from the Orakei record and from other regional lake sediment records, but more detailed comparison requires additional proxy climate data such as pollen, organic geochemistry and biomarkers, to better understand discrepancies between some records. This study demonstrated the great potential of the Orakei record for paleoclimate inference and the applicability of micro-XRF core scanning data for addressing questions about paleoclimate and paleoenvironment. It also highlighted past intervals that require further study.

Holocene climate evolution and human activity as recorded by the sediment record of lake Diss Mere, England

“…Additionally, the link between depositional changes and environmental and/or climate variability is not straightforward. As a result, it is common practice to complement the XRF core scanning data with additional proxies through a multiproxy approach such as microfacies analysis, pollen and hyperspectral imaging, to ensure that informed interpretations are made (Martin-Puertas et al, 2017;Peti and Augustinus, 2022;Zander et al, 2021).…”

“…Naeher et al, 2013;Evans et al, 2019;Makri et al, 2021), ln(Fe/Ti) (e.g. Aufgebauer et al, 2012;Peti and Augustinus, 2022) and sulphur (S clr ) (e.g. Żarczyński et al, 2019).…”

Understanding Causes of Water Quality Decline in an Aotearoa New Zealand Ecosanctuary through Paleoenvironmental Analysis

“…Micro-XRF spectrometry has been used in a few paleolimnological studies in Aotearoa to determine the ecological history of lakes, both alone and with other proxies (e.g., Gregersen et al, 2022;Short et al, 2022). Detrital influx is commonly investigated by micro-XRF proxies and has generally been successful in determining changes in catchment input over time (see Evans et al, 2019;Peti & Augustinus, 2022). Additionally, incorporation of elements that co-vary has allowed for further analyses via micro-XRF spectrometry, including nutrient influx and biological processes (see Evans et al, 2019;Peti & Augustinus, 2022).…”

“…Detrital influx is commonly investigated by micro-XRF proxies and has generally been successful in determining changes in catchment input over time (see Evans et al, 2019;Peti & Augustinus, 2022). Additionally, incorporation of elements that co-vary has allowed for further analyses via micro-XRF spectrometry, including nutrient influx and biological processes (see Evans et al, 2019;Peti & Augustinus, 2022).…”