the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Subaqueous speleothems as archives of groundwater recharge on Australia’s southern arid margin
Abstract. As anthropogenic climate change enhances aridity across vast regions of the globe, understanding drivers of aridification is more important than ever before. Unfortunately, arid regions globally tend to exhibit a paucity of palaeoclimate records, and the archives that are available typically comprise unconsolidated sediments prone to reworking, large dating uncertainties, and ambiguous climatic interpretations. This is certainly true of Australia’s vast continental interior, which is dominated by harsh, arid conditions. Mairs Cave, in the southern Ikara-Flinders Ranges (South Australia), is located on the southern margin of the arid zone. In the present day the cave is largely dry and there is limited evidence of active speleothem growth. However, historical records and observations throughout the cave indicate that it has been periodically flooded, suggesting the local water balance was once much more positive than it is today. The cave contains a curtain of hanging speleothems known as pendulites, which grow subaqueously when submerged in water that is saturated with respect to calcite. Geochemical evidence, including trace element concentrations, uranium isotope ratios, and Dead Carbon Fractions, all indicate that rising of the local groundwater during periods of enhanced groundwater recharge is the cause of the cave flooding events that trigger pendulite growth. Uranium-thorium dating of a pendulite retrieved from Mairs Cave has revealed two multi-millennial growth phases (68.5 to 65.4 kyr and 51.2 to 42.3 kyr) and two short bursts of growth (18.9 kyr and 16.4 kyr) during the Last Glacial Period. The absence of subsequent pendulite growth suggests that strong water deficits under warm Holocene interglacial conditions give rise to episodic, rather than persistent, cave flooding.
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Status: open (until 16 Sep 2024)
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RC1: 'Comment on egusphere-2024-1959', Anonymous Referee #1, 11 Aug 2024
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This paper presented detailed studies of a subaqueous speleothem from Mairs Cave in South Australia. By systematically analyzing the trace element concentrations, uranium isotope ratios, and Dead Carbon Fractions, the authors suggested that the enhanced groundwater recharge was the cause of the cave flooding events that trigger the pendulite growth. They indicated two multi-millennial growth phases (68.5 to 65.4 kyr and 51.2 to 42.3 kyr) and two short bursts of growth (18.9 kyr and 16.4 kyr) during the Last Glacial Period in this region, which corresponding to maximum local summer insolation.
I read this paper with great interest, because few studies were done in pendulites when comparing to stalagmites. In addition, speleothem records are very important for understanding the past hydroclimate change of this arid region. Therefore, I recommend its publication with minor revisions.
- Line 13, “As anthropogenic climate change enhances aridity across vast regions of the globe,”I think this is a debated question, not a conclusion.
- Line 38-42, the descriptions of aeolian and paleolacustrine depositions in arid region are too arbitrary. Some of them well well studied and have very good climate presentations in arid regions in the world.
- I suggest to reduce the conclusion part and make it more concise.
- The colors of different dates in Fig 7a are not easy to distinguish, you may consider to change to some striking colors.
Citation: https://doi.org/10.5194/egusphere-2024-1959-RC1 -
AC1: 'Reply to RC1', Calla Gould-Whaley, 15 Aug 2024
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We would like to sincerely thank the referee for taking the time to read our paper and for their positive feedback. Their comments have been very helpful and will be addressed in our revised submission.Citation: https://doi.org/
10.5194/egusphere-2024-1959-AC1
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