DOI: 10.26190/unsworks/30982
title: Snowy Flat bog, ACT palaeohydrology and palaeoenvironmental data

description: The file includes raw data associated with Xiangling Zheng's (2018) PhD Thesis (The reconstruction of moisture availability in south-eastern Australia during the Holocene) which can be accessed at https://doi.org/10.26190/unsworks/21130. The file includes modern testate amoebae, the results of 3x transfer functions between testate amoebae and depth to water-table at Snowy Flat Bog and the results of several other palaeoenvironmental analyses. Aspects of this work have been published as: Zheng X., Harper B.J., Hope G. and Mooney S.D. (2019) A new preparation method for testate amoebae in minerogenic sediments. Mires and Peat 29: Article 30: 1-12. https://DOI.org/10.19189/MaP.2018.OMB.380 Zheng X., Amesbury M.J., Hope G., Martin L.F. and Mooney S.D. (2019) Testate amoebae as a hydrological proxy for reconstructing water table depth in the mires of south-eastern Australia. Ecological Indicators 96: 701-710. https://doi.org/10.1016/j.ecolind.2018.09.019
description: All methods are fully described in Xiangling Zheng's (2018) PhD Thesis (The reconstruction of moisture availability in south-eastern Australia during the Holocene) which can be accessed at https://doi.org/10.26190/unsworks/21130. Here is a summary: 1. Sampling for modern testate amoebae and water table depth (WTD) Between 9 and 12 samples were taken at each site (except at Coronet Creek, where 1 sample, was taken as the site is very small and homogenous with a constant WTD). At all other sites 3 or 4 samples were taken along 3 or 4 transects, and these transects were of less than 3 metres in length and each covered the local range of WTD, often from the top of the hummocks to the lawn or the pool of the hollow. In all cases the peat or moss surface was taken as zero depth, with negative WTD values representing a subsurface water-table and positive values standing water. Modern sediment samples were collected from 5-10 cm depth. Modern samples from Sphagnum-dominated sites are usually taken from below the uppermost living moss. The more minerogenic sites were also sampled from 5-10 cm. When sampling from within pools, the top 5cm of the sediment was kept. WTD was measured once after the water level stabilised in an open pit or as standing water in the pools. Water samples from this pit or from the pools were also taken for laboratory analysis of pH and electrical conductivity (EC). The moisture content of the modern sediment samples was measured as mass lost after 24 hours in a 105degC fan forced oven. The laboratory method for the concentration of the modern testate amoebae consisted of (1) dispersal (with detergent overnight), (2) sieving, and (3) the retained fraction was then mixed with water, acetone, sodium hydroxide (in that order) and then placed on a preheated hotplate and then sieved again. Three nested sieves (250, 215 and 20 micron) were and the material retained between the 215 and 20 μm sieves was used for subsequent preparation or for the quantification of the testate amoebae. 2. Sampling at Snowy Flat Bog Cores of more consolidated sediments were retrieved from top of a hummock (35°33'46.21"S, 148°47'1.75"E) on the 15th December 2016 with a D-section corer, covering the depths from 110 to 267 cm. To sample the uppermost material monoliths were sampled from a Sphagnum hummock approximately 1.5 m to the west of the D-section cores using a saw on the 12th February 2018. This 106 cm-long monolith was recovered in three sections covering the depths of 0-45, 35-78 and 70-106 cm. (Sub)fossil testate amoebae were quantified in both the upper material recovered in the monolith sections (0-106 cm) and from the D-section cores (110-267 cm). Within the monolith cores, 8 samples were analysed (0-10 cm, 25-30 cm, 50-52 cm, 70-72 cm, 80-82 cm, 90-92 cm, 99-101 cm and 104-106 cm). Within the D-section cored sediments, 0.5 cm wide sections were taken at a 3-cm interval from the depth of 110 cm to 221 cm. Two extra samples were processed and quantified at depths representing 210.5 cm and 213.5 cm: these were added later, to confirm preliminary findings. This resulted in a total of 48 samples analysed between a depth of 0 cm and 221 cm at Snowy Flat. Testate amoebae were prepared following the new method described for minerogenic sediments in Zheng et al. (2019 https://DOI.org/10.19189/MaP.2018.OMB.380). This consisted of a mild-alkaline-digestion (NaOH + acetone) and dispersant (sodium pyrophosphate) treatments. At least 50 individual testate amoebae were counted for each depth sample if the number of added Lycopodium spores exceeded 200, otherwise counting stopped at 200 Lycopodium spores. 3. Radiocarbon dating and age-depth modelling Samples for radiocarbon dating were taken at nine depths (110, 115.5-117.5, 153-155, 180-182, 202-204, 227-229, 235-237, 243-245, 250-252 cm) and measured by Accelerator Mass Spectrometry (AMS) by Beta Analytic Dating Laboratory and Waikato Radiocarbon Dating Laboratory. In a few cases these radiocarbon determinations were based on short-lived plant macrofossils, which were selected by dispersing the samples in RO water and careful sorting under magnification. In most cases macrofossils were not available in the sediment and so larger charcoal particles were used in the majority of 14C dates, and these were isolated by immersion in 4% sodium hypochlorite (bleach) overnight to remove extraneous organic material and then wet-sieving at 250 m. Radiocarbon analyses were undertaken using standard protocols. In addition to radiocarbon dating, the first appearance of the pollen of the exotic genus Pinus at 105 cm in the upper monoliths was used to approximate the time of European arrival. This additional chronological control represents 50 ±30 yr BP (AD 1900, with a range of AD 1870 to 1930). The SHCal13 curve was used in the calibration of these radiocarbon ages. An age-depth model was developed using ‘Bacon’ which uses a Bayesian, hierarchical model with autoregressive gamma processes. In this research, the surface sample at 0 cm was set as the sampling year with 1-year error to constrain the starting point. To overcome changes in the annual accumulation rate of the Snowy Flat Bog sediments two boundaries at 106 cm and 190 cm were added to the Bacon modelling, and model parameters (acc.mean and acc.shape) were adjusted to match. 4. Derivation of transfer functions Water table depth (WTD) reconstruction was derived from the transfer functions that were developed and tested in Zheng et al. (2019 https://doi.org/10.1016/j.ecolind.2018.09.019). That work demonstrated that an all-species model and the modern analogue technique (MAT) had the best performance, followed by weighted average with classical de-shrinking method (WA.cla). Although a Gaussian logit regression with maximum likelihood calibration (ML) model was found to provide a poorer performance, it was used for comparison. Reconstructed WTD was detrended and normalized using z-scores. 5. Loss-on-ignition One cubic centimetre (cm3) of sediments was taken from contiguous 1 cm intervals down the core. The mass of the subsamples was first determined and then they were placed in a 105°C fan forced oven for 24 hours. Their mass was re-determined to obtain the oven-dry mass (gOD/cm3). These oven-dried subsamples were then placed in a muffle furnace preheated to 550°C for 2 hours and their mass redetermined. Organic matter content was calculated gravimetrically, as the mass lost between the oven-dried and combusted material as a percentage of the oven-dry mass. 6. Charcoal concentration Charcoal was analysed using wet sieving. Contiguous volumetric subsamples were taken at 0.5 or 1 cm intervals and treated with 4% sodium hypochlorite (bleach) for 24 hours. The subsamples were then gently washed through a 250 µm sieve and the collected material transferred to petri dishes, digitally photographed and analysed using image analysis software. Charcoal concentration was expressed as an area (mm2/cm3). 7. XRF core scanning of the Snowy Flat Bog sediment core An ITRAX core scanner (Cox Analytical, Sweden) was used to measure the X-ray fluorescence (XRF) of the Snowy Flat Bog sediment core at the Mark Wainwright Analytical Centre (MWAC), at UNSW. The MWAC XRF system uses an excitation source provided by a 35 Kv Molybdenum (Mo) tube. The non-destructive scanning of geochemical elements was conducted at a 4 mm interval on each point for 20 seconds.