Speleothems as indicators of wet and dry periods

Fairchild, Ian J.; McMillan, Emily A.

doi:10.5038/1827-806x.36.2.2

Cited by 73 publications

(48 citation statements)

References 34 publications

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“…In the Australian setting, Mg/Ca in speleothems has been shown to be a reliable recorder of effective rainfall (Fairchild and Treble, 2009;Treble et al, 2003;McDonald et al, 2004) because longer water residence times increase the Mg/Ca in speleothem drip water (Fairchild et al, 2000;Fairchild and McMillan, 2007). This relationship has been supported by comparison of recent speleothem records to instrumental data sets (Treble et al, 2003).…”

Section: Speleothemssupporting

confidence: 55%

Low-resolution Australasian palaeoclimate records of the last 2000 years

et al. 2017

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Abstract. Non-annually resolved palaeoclimate records in the Australasian region were compiled to facilitate investigations of decadal to centennial climate variability over the past 2000 years. A total of 675 lake and wetland, geomorphic, marine, and speleothem records were identified. The majority of records are located near population centres in southeast Australia, in New Zealand, and across the maritime continent, and there are few records from the arid regions of central and western Australia. Each record was assessed against a set of a priori criteria based on temporal resolution, record length, dating methods, and confidence in the proxy-climate relationship over the Common Era. A subset of 22 records met the criteria and were endorsed for subsequent analyses. Chronological uncertainty was the primary reason why records did not meet the selection criteria. New chronologies based on Bayesian techniques were constructed for the high-quality subset to ensure a consistent approach to age modelling and quantification of age uncertainties. The primary reasons for differences between published and reconstructed age-depth models were the consideration of the non-singular distribution of ages in calibrated 14 C dates and the use of estimated autocorrelation between sampled depths as a constraint for changes in accumulation rate. Existing proxies and reconstruction techniques that successfully capture climate variability in the region show potential to address spatial gaps and expand the range of climate variables covering the last 2000 years in the Australasian region. Future palaeoclimate research and records in Australasia could be greatly improved through three main actions: (i) greater data availability through the public archiving of published records; (ii) thorough characterisation of proxy-climate relationships through site monitoring and climate sensitivity tests; and (iii) improvement of chronologies through coretop dating, inclusion of tephra layers where possible, and increased date density during the Common Era.

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Section: Speleothemssupporting

confidence: 55%

Low-resolution Australasian palaeoclimate records of the last 2000 years

et al. 2017

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“…On the one hand, it is possible that the dry conditions late in the MEHI not only brought lesser water recharge to the cave, but also lowered the hydraulic head, and increased the rate of evapotranspiration in the vadose zone. This condition possibly allowed more air to penetrate the aquifer, perhaps enhancing prior carbonate precipitation (PCP) in pores and conduits above the caves (e.g., Fairchild and McMillan, 2007;Fairchild et al, 2000;Johnson et al, 2006;Karmann et al, 2007;McDonald et al, 2007). This process must have blocked water moving towards Stalagmites ANJB-2 and MAJ-5.…”

Section: Malagasy Mid-holocene Intervalmentioning

confidence: 99%

Three distinct Holocene intervals of stalagmite deposition and nondeposition revealed in NW Madagascar, and their paleoclimate implications

et al. 2017

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Abstract. Petrographic features, mineralogy, and stable isotopes from two stalagmites, ANJB-2 and MAJ-5, respectively from Anjohibe and Anjokipoty caves, allow distinction of three intervals of the Holocene in NW Madagascar. The Malagasy early Holocene (between ca. 9.8 and 7.8 ka) and late Holocene (after ca. 1.6 ka) intervals (MEHI and MLHI, respectively) record evidence of stalagmite deposition. The Malagasy middle Holocene interval (MMHI, between ca. 7.8 and 1.6 ka) is marked by a depositional hiatus of ca. 6500 years.Deposition of these stalagmites indicates that the two caves were sufficiently supplied with water to allow stalagmite formation. This suggests that the MEHI and MLHI intervals may have been comparatively wet in NW Madagascar. In contrast, the long-term depositional hiatus during the MMHI implies it was relatively drier than the MEHI and the MLHI.The alternating wet-dry-wet conditions during the Holocene may have been linked to the long-term migrations of the Intertropical Convergence Zone (ITCZ). When the ITCZ's mean position is farther south, NW Madagascar experiences wetter conditions, such as during the MEHI and MLHI, and when it moves north, NW Madagascar climate becomes drier, such as during the MMHI. A similar wetdry-wet succession during the Holocene has been reported in neighboring locations, such as southeastern Africa. Beyond these three subdivisions, the records also suggest wet conditions around the cold 8.2 ka event, suggesting a causal relationship. However, additional Southern Hemisphere highresolution data will be needed to confirm this.

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“…5f). They are so abundant that the remaining crystals form a fragile structure that in some parts can be as In Castañar Cave dissolution of dolostones and magnesites provides initially Mg-enriched solutions in which the Mg/Ca ratio can be increased in a several ways, as for instance, by removal of Ca from the waters by processes of "prior calcite precipitation" occurring in the epikarst before the waters reach the cave atmosphere, during relatively dry periods (Fairchild & McMillan, 2007). Similar mechanism of increasing Mg/Ca ratios, by removal of Ca 2+ ions from solution, can explain the formation of hydromagnesite or huntite, which requires even higher Mg/Ca ratios and higher alkalinity than aragonite formation (Müller et al, 1972;Lippmann, 1973;Davies et al, 1977 loss results in the sequential precipitation of calcite, aragonite, huntite and hydromagnesite (Fishbeck & Müller, 1971;González & Lohmann, 1988;Hill & Forti, 1997;Casas et al, 2001).…”

Section: Controls On Primary Mineralogy Of Speleothemsmentioning

confidence: 99%

“…Speleothems can potentially yield environmental and climate proxies for paleoclimatology studies, and have been the objective of numerous research studies for the last twenty or thirty years (McDermott, 2004;Fairchild et al, 2007;Frisia & Borsato, 2010). They are attractive to paleoclimatologists because: i) they can grow continuously and be precisely dated through a series of techniques (Frisia & Borsato, 2010); ii) they capture the cave response to the external environment during their formation (cave temperature is around the mean annual external temperature and dripwater discharge reflects the amount of infiltration) (McDermott, 2004); and iii) they generally show little secondary alteration (Fairchild et al, 2006).…”

Section: Introductionmentioning

confidence: 99%