https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:48378 Wed 15 Mar 2023 13:55:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:13485 Wed 11 Apr 2018 12:01:50 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50135 Tue 04 Jul 2023 14:02:38 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18114 13C values are linked to low δ¹³C values of cave air and drip water during that time. This observation corresponds to times of reduced cave ventilation, high pCO₂ of cave air, low drip water pH, lower calcite supersaturation and typically high drip rates. In contrast, the translucent, dense laminae represent more or less complete lateral coalescence (inclusion-free) during the cold season (high calcite, drip water and cave air δ¹³C values), i.e. times of enhanced cave ventilation, low cave air pCO₂, increased drip water pH, relatively high calcite supersaturation and typically low drip rates. In essence, the relative development of the two lamina types reflects changes in the seasonality of external air temperature and precipitation, with a strong control of the winter air temperature on the intensity of cave-air exchange. Thick translucent, dense laminae are favoured by long, cold and wet winters and such conditions may be related closely to the North Atlantic Oscillation mode (weak westerlies) and enhanced Mediterranean cyclone activity during the cold season. Studies of speleothem lamination can thus help to better understand (and quantify) the role of seasonality changes, for example, during rapid climate events.]]> Sat 24 Mar 2018 08:04:36 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19954 Sat 24 Mar 2018 07:58:33 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39968 3) crystals from weak solutions of (NH₄)₂CO₃, CaCl₂ and NH₄Cl. These solutions also contained peat DOM (from 0 to 15 mgC/L). Fluorescence 3D excitation-emission matrix (3D EEM) analysis showed a strong, positive correlation between [DOM] in the parent-solution, and [DOM] in the calcite. Calcite precipitation was reduced at high DOM concentrations, potentially indicating inhibition of crystallisation. Partition coefficient values showed that DOM_aq was subtly preferentially incorporated into calcite. Scanning electron microscope images indicated that the crystal structures were heavily influenced by DOM adsorption with finer, smooth-faced, rhombohedral crystals forming in growth solutions with low aqueous [DOM] (0–5 mgC/L), and prismatic, ‘impure’ crystals produced at high aqueous [DOM] (10 and 15 mgC/L). Overall, our results indicate that authigenic carbonates are likely to faithfully record variations in aqueous [DOM] within the natural range of DOM concentrations in representative freshwater systems (caves, soil water), and that crystal habits are altered by aqueous [DOM] within their growth solutions. We also applied our findings to three flowstones collected from three New Zealand caves which vary in climatic, vegetation and hydrological regimes. We conclude that differences in initial aqueous [DOM] do indeed control incorporation of DOM into calcite, and thus 3D EEM fluorescence can be used to reconstruct original aqueous [DOM] from authigenic carbonates.]]> Fri 15 Jul 2022 10:18:17 AEST ]]>