Semi-arid zone caves: Evaporation and hydrological controls on δ18O drip water composition and implications for speleothem paleoclimate reconstructions

Monika Markowska, Andy Baker, Martin S. Andersen, Catherine N. Jex, Mark O. Cuthbert, Gabriel C. Rau, Peter W. Graham, Helen Rutlidge, Gregoire Mariethoz, Christopher E. Marjo, Pauline C. Treble, Nerilee Edwards

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)
223 Downloads (Pure)

Abstract

Oxygen isotope ratios in speleothems may be affected by external processes that are independent of climate, such as karst hydrology and kinetic fractionation. Consequently, there has been a shift towards characterising and understanding these processes through cave monitoring studies, particularly focussing on temperate zones where precipitation exceeds evapotranspiration. Here, we investigate oxygen isotope systematics at Wellington Caves in semi-arid, SE Australia, where evapotranspiration exceeds precipitation. We use a novel D2O isotopic tracer in a series of artificial irrigations, supplemented by pre-irrigation data comprised four years of drip monitoring and three years of stable isotope analysis of both drip waters and rainfall. This study reveals that: (1) evaporative processes in the unsaturated zone dominate the isotopic composition of drip waters; (2) significant soil zone 'wetting up' is required to overcome soil moisture deficits in order to achieve infiltration, which is highly dependent on antecedent hydro-climatic conditions; (3) lateral flow, preferential flow and sorption in the soil zone are important in redistributing subsurface zone water; (4) isotopic breakthrough curves suggest clear evidence of piston-flow at some drip sites where an older front of water discharged prior to artificial irrigation water; and (5) water residence times in a shallow vadose zone (

Original languageEnglish
Pages (from-to)285-301
Number of pages17
JournalQuaternary Science Reviews
Volume131
Issue numberPart B
Early online date26 Nov 2015
DOIs
Publication statusPublished - 1 Jan 2016

Keywords

  • Drip water
  • Evaporation
  • Paleoclimate
  • Semi-arid
  • Speleothem
  • Stable isotopes
  • Tracing

ASJC Scopus subject areas

  • Geology
  • Global and Planetary Change
  • Ecology, Evolution, Behavior and Systematics
  • Archaeology
  • Archaeology

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