https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49765 Wed 31 May 2023 09:27:40 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:55376 Wed 22 May 2024 15:15:39 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47773 Wed 22 Mar 2023 18:06:21 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30179 18O and δ¹³C minima. Periods of lowered recharge are indicated by ¹⁸O and δ¹³ enrichment, primarily affecting δ¹⁸O, argued to be driven by evaporation of shallow soil/epikarst water in this water-limited environment. A hydrological driver is supported by calcite fabric changes. These include the presence of laminae, visible organic colloids, and occasional dissolution features, related to recharge, as well as the presence of sediment bands representing cave floor flooding. A shift to slower-growing, more compact calcite and an absence of lamination is interpreted to represent reduced recharge. The Mairs Cave record indicates that the Flinders Ranges were relatively wet during the LGM and early deglaciation, particularly over the interval 18.9–15.8 ka. This wetter phase ended abruptly with a shift to drier conditions at 15.8 ka. These findings are in agreement with the geomorphic archives for this region, as well as the timing of events in records from the broader Australasian region. The recharge phases identified in the Mairs Cave record are correlated with, but antiphase to, the position of the westerly winds interpreted from marine core MD03-2611, located 550 km south of Mairs Cave in the Murray Canyons region. The implication is that the mid-latitude westerlies are located further south during the period of enhanced recharge in the Mairs Cave record (18.9–16 ka) and conversely are located further north when greater aridity is interpreted in the speleothem record. A further comparison with speleothem records from the northern Australasian region reveals that the availability of tropical moisture is the most likely explanation driving enhanced recharge, with further amplification of recharge occurring during the early half of Heinrich Stadial 1 (HS1), possibly influenced by a more southerly displaced Intertropical Convergence Zone (ITCZ). A rapid transition to aridity at 15.8 ka is consistent with a retraction of this tropical moisture source.]]> Wed 21 Aug 2019 09:48:28 AEST ]]> 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:30180 2 drawdown during the last glacial period were linked to iron (Fe) fertilization of subantarctic surface waters. The principal source of this Fe is thought to be dust transported from southern mid-latitude deserts. However, uncertainty exists over contributions to CO₂ sequestration from complementary Fe sources, such as the Antarctic ice sheet, due to the difficulty of locating and interrogating suitable archives that have the potential to preserve such information. Here we present petrographic, geochemical and microbial DNA evidence preserved in precisely dated subglacial calcites from close to the East Antarctic Ice-Sheet margin, which together suggest that volcanically-induced drainage of Fe-rich waters during the Last Glacial Maximum could have reached the Southern Ocean. Our results support a significant contribution of Antarctic volcanism to subglacial transport and delivery of nutrients with implications on ocean productivity at peak glacial conditions.]]> Wed 11 Apr 2018 17:19:42 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30186 14C ages ranged from 2232 to 2889 cal yr BP, with 95.4% probability age range in the youngest and oldest samples of 2153–2337 and 2342–3449 cal yr BP respectively. The median age of the more modern dripstone was 336 cal yr BP, with a 95.4% probability age range of 148–486 cal yr BP. These results provide very approximate ball-park estimates of the age of the sample, but are consistently too old when compared to the known maximum ages of formation. It is hypothesised that this offset is due to a combination of the nature of the organic carbon transported from the source organic matter pools, and reworking of both modern and old organic carbon by in situ microbial communities.]]> Wed 04 Sep 2019 09:39:24 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47316 Tue 30 Apr 2024 09:51:07 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:41756 Tue 21 Mar 2023 18:48:39 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37522 230Th content. This poses problems in establishing reliable trends and periodicities for droughts and pluvial episodes in a region vulnerable to climate change. Here we constrain the chronology of a Cook Islands stalagmite using synchrotron µXRF two-dimensional mapping of Sr concentrations coupled with growth laminae optical imaging constrained by in situ monitoring. Unidimensional LA-ICP-MS-generated Mg, Sr, Ba and Na variability series were anchored to the 2D Sr and optical maps. The annual hydrological significance of Mg, Sr, Ba and Na was tested by principal component analysis, which revealed that Mg and Na are related to dry-season, wind-transported marine aerosols, similar to the host-rock derived Sr and Ba signatures. Trace element annual banding was then used to generate a calendar-year master chronology with a dating uncertainty maximum of ± 15 years over 336 years. Our approach demonstrates that accurate chronologies and coupled hydroclimate proxies can be obtained from speleothems formed in tropical settings where low seasonality and problematic U–Th dating would discourage the use of high-resolution climate proxies datasets.]]> Tue 15 Nov 2022 14:35:44 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54581 Tue 14 May 2024 15:10:28 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:33010 SO₄ =(mSO₄/mCO₃)_solid/(mSO₄/mCO₃)_solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of D_SO₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, D_SO₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of D_SO₄ were compared with D_SO₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, D_SO₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted D_SO₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of D_SO₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind D_SO₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.]]> Tue 03 Sep 2019 18:19:27 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45155 18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.]]> Thu 27 Oct 2022 14:49:38 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54922 Thu 21 Mar 2024 13:41:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54914 Thu 21 Mar 2024 12:03:59 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49225 20 Megapixels) hardly feasible. For concentrations above 20 ppm the fast mapping (dwell time < 5 ms) through S-μXRF is by far the best methodology to visualise chemical annual cycles in stalagmites.]]> Sun 07 May 2023 09:44:11 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49220 Sun 07 May 2023 09:37:55 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:6878 Sat 24 Mar 2018 10:24:42 AEDT ]]> https://ogma.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://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10263 Sat 24 Mar 2018 08:13:06 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:11476 Sat 24 Mar 2018 08:10:27 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10909 Sat 24 Mar 2018 08:07:41 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:19953 Sat 24 Mar 2018 07:58:32 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:6876 Sat 24 Mar 2018 07:49:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:6877 Sat 24 Mar 2018 07:49:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30183 2 contribution to the total dissolved inorganic carbon (DIC). Pronounced millennial-scale shifts in DCP and relatively small coeval but antipathetic changes in δ¹³C are modulated by the effects of hydrological variability on open and closed-system dissolution, SAD and prior calcite precipitation. Hence, the DCP in Corchia Cave speleothems represents an additional proxy for rainfall amount.]]> Sat 24 Mar 2018 07:41:34 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28922 Homo neanderthalensis, with some phenetic peculiarities that appear consistent with a chronology ranging from 172 ± 15 ka to 130.1 ± 1.9 ka. Thus, the skeleton from Altamura represents the most ancient Neanderthal from which endogenous DNA has ever been extracted.]]> Sat 24 Mar 2018 07:31:24 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27242 100 nm) of soils, but in the fine colloidal (< 100 nm) and nominally dissolved (< 1 nm) fractions of dripwaters. The concentration of Cu, Ni and Co in dripwater samples across all sites were well correlated (R2 = 0.84 and 0.70, Cu vs. Ni, Cu vs. Co, respectively), indicating a common association. Furthermore, metal ratios (Cu:Ni, Cu:Co) were consistent with NICA-Donnan n1 humic binding affinity ratios for these metals, consistent with a competitive hierarchy of binding affinity (Cu > Ni > Co) for sites in colloidal or dissolved NOM. Large shifts in Cu:Ni in dripwaters coincided with high fluxes of particulate OC (following peak infiltration) and showed increased similarity to ratios in soils, diagnostic of qualitative changes in NOM supply (i.e. fresh inputs of more aromatic/hydrophobic soil organic matter (SOM) with Cu outcompeting Ni for suitable binding sites). Results indicate that at high-flows (i.e. where fracture-fed flow dominates) particulates and colloids migrate at similar rates, whereas, in slow seepage-flow dripwaters, particulates (> 1 μm) and small colloids (1–100 nm) decouple, resulting in two distinct modes of NOM–metal transport: high-flux and low-flux. At the hyperalkaline drip site PE1 (in Poole's Cavern), high-fluxes of metals (Cu, Ni, Zn, Ti, Mn, Fe) and particulate NOM occurred in rapid, short-lived pulses following peak infiltration events, whereas low-fluxes of metals (Co and V > Cu, Ni and Ti) and fluorescent NOM (< ca. 100 nm) were offset from infiltration events, probably because small organic colloids (1–100 nm) and solutes (< 1 nm) were slower to migate through the porous matrix than particulates. These results demonstrate the widespread occurrence of both colloidal and particulate NOM–metal transport in cave dripwaters and the importance of karst hydrology in affecting the breakthrough times of different species. Constraints imposed by soil processes (colloid/particle release), direct contributions of metals and NOM from rainfall, and flow-routing (colloid/particle migration) are expected to determine the strength of correlations between NOM-transported metals in speleothems and climatic signals. Changes in trace metal ratios (e.g. Cu:Ni) in speleothems may encode information on NOM composition, potentially aiding in targeting of compound-specific investigations and for the assessment of changes in the quality of soil organic matter.]]> Sat 24 Mar 2018 07:29:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26553 Sat 24 Mar 2018 07:26:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25220 Sat 24 Mar 2018 07:14:01 AEDT ]]> https://ogma.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 ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25047 Sat 24 Mar 2018 07:10:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50783 Sat 05 Aug 2023 11:08:33 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:54972 Mon 25 Mar 2024 15:19:44 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50776 Mon 22 Apr 2024 11:47:11 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:46284 Mon 14 Nov 2022 15:48:51 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45464 26Al and ¹⁰Be) in quartz grains allowed to estimate a minimum burial age of 5.25 Ma based on the mean sediment transport time at the surface and infer original altitude of the catchment area. Detrital apatite fission-track (AFT) and U-Pb dating on zircons provide information on the source, both from a regional and altitude (exhumation) perspective. Two populations of detrital AFT ages center at 17 (−2.3 + 2.6) Ma and 23 (−3.3 + 3.9) Ma, whereas the main detrital zircon U-Pb age populations are younger than 40 Ma. These correspond to intrusive and metamorphic sources nowadays outcropping exclusively above 2,200–2,300 m a.s.l. in Northern Adamello and Tonale. The results point to a late Miocene erosion and infilling of the cave by allochtonous sediments, with important implications on the timing of cave speleogenesis, as well as the paleogeographical connection, tectonic evolution and uplift of different structural units of the Alps. The roundness and the well sorted size of the quartz grains suggest a fluvial or aeolian origin, possibly recycled by glacial activity related to cold events reported in high latitude areas of the world at 5.75 and 5.51 Ma. These glacial phases have never been documented before in the Alps. This information confirms that the valleys dividing these geological units were not yet deeply entrenched during the onset of the Messinian Salinity Crisis (5.6–5.5 Ma), allowing an efficient transport of sediments across major tectonic lineaments of the Alps. This study shows the potential of cave sediments to provide information not only on the age of speleogenesis but also on the paleogeography of a wide area of the Alps during the late Miocene.]]> Fri 28 Oct 2022 14:30:18 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47225 Fri 16 Dec 2022 10:37:32 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:52979 130 ka), the morphology of Altamura suggests that the archaic traits it retains may have been originated by geographic isolation of the early Neanderthal populations from Southern Italy.]]> Fri 03 Nov 2023 15:30:17 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49771 Fri 02 Jun 2023 17:37:40 AEST ]]>