Corrigendum to “Palaeohydrogeology and Transport Parameters Derived from 4He and Cl Profiles in Aquitard Pore Waters in a Large Multilayer Aquifer System, Central Australia”

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In the article titled “Palaeohydrogeology and Transport Parameters Derived from 4 He and Cl Profiles in Aquitard Pore Waters in a Large Multilayer Aquifer System, Central Australia” [1], Mr. Stanley D. Smith was missing from the authors’ list. Mr. Stanley made a significant contribution in helping with the core sampling protocol, canister leak testing, and discussing modelling methods. The corrected authors’ list is shown above

Palaeohydrogeology and Transport Parameters Derived from 4He and Cl Profiles in Aquitard Pore Waters in a Large Multilayer Aquifer System, Central Australia

A study of chloride and 4He profiles through an aquitard that separates the Great Artesian Basin from the underlying Arckaringa Basin in central Australia is presented. The aquitard separates two aquifers with long water residence times, due to low recharge rates in the arid climate. One-dimensional solute transport models were used to determine the advective flux of groundwater across the aquitard as well as establish any major changes in past hydrological conditions recorded by variations of the pore water composition. This in situ study showed that both diffusion and slow downward advection (vz=0.7 mm/yr) control solute transport. Numerical simulations show that an increase in chloride concentration in the upper part of the profile is due to a reduction in recharge in the upper aquifer for at least 3000 years. Groundwater extraction since 2008 has likely increased chloride and 4He concentrations in the lower aquifer by pulling up water from deeper layers; however, there has been insufficient time for upward solute transport into the pore water profile by diffusion against downward advection. The transport model of 4He and chloride provides insight into how the two aquifers interact through the aquitard and how climate change is being recorded in the aquitard profile

Detecting inter-aquifer leakage in areas with limited data using hydraulics and multiple environmental tracers, including He-4, Cl-36/Cl, C-14 and Sr-87/Sr-86

The investigation of regionally extensive groundwater systems in remote areas is hindered by a shortage of data due to a sparse observation network, which limits our understanding of the hydrogeological processes in arid regions. The study used a multidisciplinary approach to determine hydraulic connectivity between the Great Artesian Basin (GAB) and the underlying Arckaringa Basin in the desert region of Central Australia. In order to manage the impacts of groundwater abstraction from the Arckaringa Basin, it is vital to understand its connectivity with the GAB (upper aquifer), as the latter supports local pastoral stations and groundwater-dependent springs with unique endemic flora and fauna. The study is based on the collation of available geological information, a detailed analysis of hydraulic data, and data on environmental tracers. Enhanced inter-aquifer leakage in the centre of the study area was identified, as well as recharge to the GAB from ephemeral rivers and waterholes. Throughout the rest of the study area, inter-aquifer leakage is likely controlled by diffuse inter-aquifer leakage, but the coarse spatial resolution means that the presence of additional enhanced inter-aquifer leakage sites cannot be excluded. This study makes the case that a multi-tracer approach along with groundwater hydraulics and geology provides a tool-set to investigate enhanced inter-aquifer leakage even in a groundwater basin with a paucity of data. A particular problem encountered in this study was the ambiguous interpretation of different age tracers, which is attributed to diffusive transport across flow paths caused by low recharge rates.ISSN:1431-2174ISSN:1435-015

Ubiquitous karst hydrological control on speleothem oxygen isotope variability in a global study

Speleothem oxygen isotopic (δ18O) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem δ18O to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem δ18O values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater δ18O variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem δ18O records

δ13C and δ18O record of Stalagmite GL-S2 from the Golgotha Cave in southwest Western Australia

GolgothaCave_GLS2_stalagmite_O&C_isotopes: median depth, d18O and d13C values in VPDB. Chronology is that used for Treble et al (2022)

Age chronology based on U/Th ages, bomb pulse 14C data and year of collection (2012) of Stalagmite GL-S1 from the Golgotha Cave in southwest Western Australia

Stalagmite GL-S1 chronology in ka CE based on U/Th ages, bomb pulse 14C data and year of collection (2005). Treble et al. (2022) used 17th percentile age-depth model

Golgotha Cave stalagmite records 1 ka

Stalagmites GL-S1, GL-S2, GL-S3 and GL-S4 were collected under scientific license issued by Western Australia's Department of Biodiversity, Conservation and Attractions from Golgotha Cave (34.1°S, 115.1°E) in southwest Western Australia, with collection dates of 2005, 2005, 2008 and 2012, respectively. Cave location is rounded to nearest tenth of a degree as exact locations not disclosed for cave conservation purposes. Speleothems were collected for paleoclimate and paleohydrology studies. Golgotha Cave is located in Eucalyptus forest with dense understorey in the Leeuwin-Naturaliste National Park. The hostrock is Quaternary aeolinite and the soil thickness is variable with measurements ranging from 0.3-3 m deep. The cave entrance is 70 m above sea level. Stalagmites GL-S1 and GL-S4 are located approximately 60 m from the entrance where the limestone thickness overhead is 30 m while GL-S2 and GL-S3 are located approximately 90 m from the entrance where the limestone thickness overhead is 40 m. Mean annual site temperature is 15.6 ±0.5°C and mean annual rainfall is 1101±157 mm (1911-2018 period; Australian Bureau of Meteorology AWRA-L dataset http://www.bom.gov.au/water/landscape. Inside the cave, temperature ranges from 14.5-14.8°C, windspeed is low (≤0.03 m s-1) and relative humidity ranges from 98-100% (Treble et al 2019). Each speleothem was sectioned along the growth axis and milled using a Taig micromill to produce homogenised powders representing increments of 0.1 to 0.2 mm, depending on the speleothem growth rate. Powders were weighed to 180–220 μg and analysed for O and C isotopic values (δ18O and δ13C) using a Finnigan MAT-251 isotope ratio mass spectrometer coupled to a Kiel I carbonate device, or a Thermo MAT-253 isotope ratio mass spectrometer coupled to a Kiel IV carbonate device (using 110–130 μg samples), at the Research School of Earth Sciences, ANU. Analyses were calibrated using NBS-19 standard (δ18Ov-PDB = -2.20 ‰ and δ13Cv-PDB = 1.95 ‰). A further linear correction for δ18O measurements was carried out using the NBS-18 standard (δ18Ov-PDB = -23.0 ‰). The original delta values for NBS-19 and NBS-18 are used to maintain consistency of results through time in the RSES Stable Isotope Facility. Analytical precision for the analyses reported here (NBS-19) are ±0.04 ‰ for δ18O and ±0.02 ‰ for δ13C (N=236) for the MAT-251; and ±0.05 ‰ for δ18O and ±0.01 ‰ (N=27) for the MAT-253 instrument (±1σ standard deviation). Speleothem chronologies were determined by combining information from the date of collection, bomb pulse chronology, laminae counting of annual Sr concentration and U-series disequilibrium (see Supplementary Table 8 in Treble et al., 2022). For GL-S1, the age-depth model for 17th percentile was used in Treble et al., (2022) and the 50th percentile used for other stalagmites