https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:12517 DIC values are already higher (by about 1‰) than those of soil water due to dissolution of the carbonate rock. A subsequent systematic shift to even higher δ¹³C values, from −11.5‰ in the cave drips to about −8‰ calculated for the solution film on top of stalagmites, is related to degassing on the stalagmite top and equilibration with the cave air. Mass-balance modelling of C fluxes reveals that a very small percentage of isotopically depleted cave air CO₂ evolves from the first phase of dripwater degassing, and shifts the winter cave air composition toward slightly more depleted values than those calculated for equilibrium. The systematic ¹³C-enrichment from the soil to the stalagmites at Grotta di Ernesto is independent of drip rate, and forced by the difference in pCO₂ between cave water and cave air. This implies that speleothem δ¹³C values may not be simply interpreted either in terms of hydrology or soil processes.]]> Sat 24 Mar 2018 08:16:02 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:10263 Sat 24 Mar 2018 08:13:06 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:19953 Sat 24 Mar 2018 07:58:32 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:26553 Sat 24 Mar 2018 07:26:08 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:24615 _inf) ranging from 355 to 2400 m a.s.l., corresponding to infiltration mean annual temperatures (MAT_inf) between 12 and 0 °C. Since all the caves developed in pure carbonate rocks, soil pCO₂ is found to be the main factor controlling the carbonate dissolution. For this reason, the parameters controlling the carbonate-carbonic acid system and calcite saturation state (SICC) are directly correlated with the MAT_inf, which influences the vegetation zones and eventually the production of CO₂ in the soil. SI_CC linearly depends on MAT_inf (SI_CC = 0.09 MAT_inf - 0.4) and SI_CC = 0 is reached at Z_inf = 1.66 km a.s.l., corresponding to a MAT_inf = 4.4 °C. This point identifies the "speleothem limit" defined here as the elevation (or corresponding MAT_inf) above which no sparitic speleothem precipitation usually occurs. We demonstrate that due to temperature-forced changes in the soil and vegetation and subsequently SI_CC, the speleothem limit shifts to higher altitudes during maximum interglacial conditions. Speleothems from high altitude caves (1.5-2.5 km a.s.l.) thus can identify optimum interglacial periods. By contrast, speleothems formed at lower altitudes are better suited as archives of hydrological proxies. At altitudes below 1.2 km a.s.l., prior calcite precipitation (PCP) modifies percolating waters, particularly during periods of reduced infiltration. We introduce the use of the SiO₂/Ca and SO₄/Ca ratios in cave waters to complement Mg/Ca and Sr/Ca ratios as markers of PCP. SO₄ and SiO₂ are derived from atmospheric deposition and siliciclastic minerals in the soil zone, rather than carbonate host rocks (as in the case of Mg and Sr). By combing shifts to higher Mg/Ca, SiO₂/Ca and SO₄/Ca ratios along their characteristics PCP lines, we improve the robustness of the interpretation that this resulted from increasing PCP, rather than incongruent calcite dissolution (ICD). Our method permits the quantification of PCP between 0% and 40% for low elevation cave waters. This novel approach has important implications for speleothem-based paleoclimate studies where the distinction between PCP and ICD can be ambiguous and, in combination with Mg/Ca and Sr/Ca ratios, permits the quantification of net infiltration and/or rainfall amount from speleothem records.]]> Sat 24 Mar 2018 07:11:54 AEDT ]]>