Quantifying respirable crystalline silica in the ambient air of the Hunter Valley, NSW - sorting the silica from the silicon

Crystalline forms of silica are known to cause lung damage for which there is no effective treatment. Silicon is abundant in crustal material and silicates are the single largest mineral grouping, with silica (SiO2) being the most abundant crustal compound. Media reports of high levels of silicon in particles in the air in the vicinity of Hunter Valley open-cut coal mines have caused community anxiety and concerns about potential health impacts on local populations. An extensive sampling campaign using continuous air quality monitoring and targeted collection of particles has been carried out in an area close to mining operations. It was determined that silicon as silica was present in the ambient air, although the concentrations of crystalline silica measured suggest that it should not should cause health problems even for sensitive individuals within the general population. The results of the research should inform more rigorous discussions of air quality management plans for fine particles in the Hunter Valley and aid discussions of community concerns over the potential health impacts of coal mining.© 2011-Clean Air Society of Australia & New Zealan

Loess and floods: High-resolution multi-proxy data of Last Glacial Maximum (LGM) slackwater deposition in the Flinders Ranges, semi-arid South Australia

Terrace remnants of late Pleistocene fine-grained valley-fill deposits (Silts) deeply entrenched by ephemeral traction load streams in arid areas remain a puzzle. They have been attributed to a variety of origins ranging from lacustrine to alluvial floodplains. We here report a centimetre-scale multi-proxy study of a 7 m section of Silts in the semi-arid Flinders Ranges of South Australia, which span the lead-up to and peak of the Last Glacial Maximum (LGM). The results of detailed lithostratigraphic mapping, high-resolution parametric particle-size analysis, Automated Mineralogy, induced magnetic susceptibility, carbon stable isotope geochemistry, and a chronostratigraphy based on 27 AMS radiocarbon and 6 luminescence ages are discussed in terms of sediment provenance, depositional environment and weathering history with the aim of reconstructing the regional palaeo-environment. The data are consistent with a fluctuating aeolian-fluvial interplay dominating the extended LGM environment with a greater impact on the landscape than all combined geomorphic processes since then. Accordingly, weathered slope mantles and loess accessions were eroded and entrained by numerous small and at least a dozen large-scale flood events, and trapped in an intra-montane floodplain extending into Brachina Gorge. Upstream of this narrow constriction, recurrent backflooding is discussed resulting in a thick sequence of layered to laminated slackwater couplets. Aggradation and degradation of valley-fills appear to be largely controlled by fine-sediment supply from the valley slopes, replenished by wind-blown dust from upwind playa lakes and source-bordering dunefields. In conclusion, this study demonstrates how dust storms and flooding rains can account for 'pluvial' features previously explained by the opposing effects of reduced precipitation and evaporation in the colder more arid glacial landscape of southern Australia. © 2010 Elsevier Ltd.David Haberlah, Martin A.J. Williams, Galen Halverson, Grant H. McTainsh, Steven M. Hill, Tomas Hrstka, Patricio Jaime, Alan R. Butcher and Peter Glasb

A White Nile megalake during the last interglacial period

The eastern Sahara Desert of Africa is one of the most climatically sensitive areas on Earth, varying from lake-studded savannah woodland to hyperarid desert over the course of a glacial-interglacial cycle. In currently semiarid Sudan there is widespread evidence that a very large freshwater lake once filled the White Nile River valley. Here we present the first quantitative estimate for the dimensions of the lake and a direct age for the emplacement of its shoreline. Using a profile dating approach with the cosmogenic nuclide 10Be, we estimate an exposure age of 109 ± 8 ka for this megalake, indicating that it probably formed during the last interglacial period. This age is supported by optically stimulated luminescence dating of Blue Nile paleochannels associated with the lake. Using a high-resolution digital elevation model, we estimate that the lake was more than 45,000 km2 in area, making it comparable to the largest freshwater lakes on Earth today. We attribute the lake’s existence to seasonal flood pulses as a result of local damming of the White Nile by a more southern position of the Blue Nile and greatly increased precipitation associated with an enhanced monsoon

Late Quaternary palaeoenvironmental change in the Australian drylands

In this paper we synthesise existing palaeoenvironmental data from the arid and semi-arid interior of the Australian continent for the period 40–0 ka. Moisture is the predominant variable controlling environmental change in the arid zone. Landscapes in this region respond more noticeably to changes in precipitation than to temperature. Depending on their location, arid zone records broadly respond to tropical monsoon-influenced climate regimes, the temperate latitude westerly systems, or a combination of both. The timing and extent of relatively arid and humid phases vary across the continent, in particular between the westerly wind-controlled temperate latitudes, and the interior and north which are influenced by tropically sourced precipitation. Relatively humid phases in the Murray-Darling Basin on the semi-arid margins, which were characterised by large rivers most likely fed by snow melt, prevailed from 40 ka to the Last Glacial Maximum (LGM), and from the deglacial to the mid Holocene. By contrast, the Lake Eyre basin in central Australia remained relatively dry throughout the last 40 ka, with lake high stands at Lake Frome around 35–30 ka, and parts of the deglacial period and the mid-Holocene. The LGM was characterised by widespread relative aridity and colder conditions, as evidenced by extensive desert dune activity and dust transport, lake level fall, and reduced but episodic fluvial activity. The climate of the deglacial period was spatially divergent. The southern part of the continent experienced a brief humid phase around ∼17–15 ka, followed by increased dune activity around ∼14–10 ka. This contrasts with the post-LGM persistence of arid conditions in the north, associated with a lapsed monsoon and reflected in lake level lows and reduced fluvial activity, followed by intensification of the monsoon and increasingly effective precipitation from ∼14 ka. Palaeoenvironmental change during the Holocene was also spatially variable. The early to mid-Holocene was, however, generally characterised by moderately humid conditions, demonstrated by lake level rise, source-bordering dune activity, and speleothem growth, persisting at different times across the continent. Increasingly arid conditions developed into the late Holocene, particularly in the central arid zone. © 2012 Elsevier Ltd

Application of Quantitative Mineralogical Analysis in Archaeological Micromorphology: a Case Study from Barrow Is., Western Australia

© 2017 Springer Science+Business Media New YorkThis study assesses the use of the Tescan Integrated Mineral Analyser (TIMA) platform, which integrates scanning electron microscopy—energy dispersive spectroscopy (SEM-EDS) chemical analysis with mineral identification software, to quantitatively determine the mineralogical composition of sediments in archaeological research. Ten samples, spanning 50,000 years of sedimentation, were examined from archaeological excavation profiles in the Boodie Cave, Barrow Island, Western Australia. TIMA mineral abundance data show a gradual change from a polymineralogic quartz-rich assemblage from ~50–12 ka to a more simple carbonate-dominate assemblage from the terminal Pleistocene. This trend is consistent with a decreasing contribution of reworked terrestrial siliciclastic sediments derived from the mainland and an increase in carbonate sediments of marine derivation, as the exposed coastal plain become submerged during post-glacial sea-level rise. SEM-EDS analysis has also provided empirical data on cultural materials, mainly bone and shell fragments that similarly reflect the increasing contribution of marine fauna into the Holocene sediments. Particularly useful is the ability of mineral mapping function of the TIMA outputs to help distinguish 16 sub-units representing sections of the main nine stratigraphic units, including at least three contiguous midden events. The SEM-EDS data indicate that the redeposited sediments were derived from the overlying midden unit, with layering reflecting differential settling of mineral phases. This study demonstrates that automated mineralogy studies using TIMA can clearly aid the identification of provenance and processes within archaeological sediments and soils

Late Quaternary floods and droughts in the Nile valley, Sudan: new evidence from optically stimulated luminescence and AMS radiocarbon dating

Our results show that the late Pleistocene Nile in northern Sudan was shifting position and actively aggrading at 145 ± 20 kyr, 83 ± 24 kyr, 32 ± 8 kyr and 20.7 ± 0.2 kyr and indicate, for the first time, a phase of high-energy flow in the White Nile at 27.8 ± 3.2 kyr, with still high but somewhat reduced flow in that river at 13.3 kyr, 10 kyr and 4.8-4.0 kyr. Beach ridges associated with a 386 m strandline of the White Nile have OSL ages of 27.5 ± 2.7 kyr and 14.5 ± 1.6 kyr. The Holocene terraces and former channels of the main Nile have ages of 11 kyr, 6.5-5.0 kyr and 4.8-4.0 kyr, after which there was a general decline in flood discharge. The now arid main Nile valley in northern Sudan was significantly wetter during the early to middle Holocene, with a lake up to 450 km2 in area, fed by an overflow channel from the early Holocene Nile between 9.5 kyr and 7.5 kyr. Previously stable late Pleistocene dunes were reactivated at intervals during the Holocene, with five samples from the White Nile valley indicating brief phases of Holocene dune activity at 9.9 ± 2.0 kyr, 9.0 ± 2.8 kyr, 6.6 ± 0.9 kyr, 4.8 ± 0.9 kyr and 2.9 ± 0.5 kyr, the earliest of which occurred within periods of generally wetter climate and higher Nile flow. The youngest freshwater shells on the Khor Abu Habl alluvial fan west of the White Nile correspond to a time of regionally wetter climate between 1.7 and 1.0 kyr. Our results suggest that millennial scale climatic instability may have been characteristic of Holocene climates in this region. © 2010 Elsevier Ltd. All rights reserved.M.A.J. Williams, F.M. Williams, G.A.T. Duller, R.N. Munro, O.A.M. El Tom, T.T. Barrows, M. Macklin, J. Woodward, M.R. Talbot, D. Haberlah, J. Flui

Kangaroo tooth enamel oxygen and carbon isotope variation on a latitudinal transect in southern Australia: implications for palaeoenvironmental reconstruction

Tooth enamel apatite carbonate carbon and oxygen isotope ratios of modern kangaroos (Macropus spp.) collected on a 900-km latitudinal transect spanning a C₃–C₄ transition zone were analysed to create a reference set for palaeoenvironmental reconstruction in southern Australia. The carbon isotope composition of enamel carbonate reflects the proportional intake of C₃ and C₄ vegetation, and its oxygen isotope composition reflects that of ingested water. Tooth enamel forms incrementally, recording dietary and environmental changes during mineralisation. Analyses show only weak correlations between climate records and latitudinal changes in δ¹³C and δ¹⁸O. No species achieved the δ¹³C values (~−1.0 ‰) expected for 100 % C₄ grazing diets; kangaroos at low latitudes that are classified as feeding primarily on C₄ grasses (grazers) have δ¹³C of up to −3.5 ‰. In these areas, δ¹³C below −12 ‰ suggests a 100 % C₃ grass and/or leafy plant (browse) diet while animals from higher latitude have lower δ¹³C. Animals from semi-arid areas have δ¹⁸O of 34–40 ‰, while grazers from temperate areas have lower values (~28–30 ‰). Three patterns with implications for palaeoenvironmental reconstruction emerge: (1) all species in semi-arid areas regularly browse to supplement limited grass resources; (2) all species within an environmental zone have similar carbon and oxygen isotope compositions, meaning data from different kangaroo species can be pooled for palaeoenvironmental investigations; (3) relatively small regional environmental differences can be distinguished when δ¹³C and δ¹⁸O data are used together. These data demonstrate that diet–isotope and climate–isotope relationships should be evaluated in modern ecosystems before application to the regional fossil record.Tom H. Brookman, Stanley H. Ambros

Climate variability over the last 35,000 years recorded in marine and terrestrial archives in the Australian region: An OZ-INTIMATE compilation

The Australian region spans some 60° of latitude and 50° of longitude and displays considerable regional climate variability both today and during the Late Quaternary. A synthesis of marine and terrestrial climate records, combining findings from the Southern Ocean, temperate, tropical and arid zones, identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35,000 years. Climate drivers include the seasonal timing of insolation, greenhouse gas content of the atmosphere, sea level rise and ocean and atmospheric circulation changes. Our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region, limiting the usefulness of this approach. Instead we have taken a spatial approach, looking to discern the patterns of change across the continent. The data identify the clearest and most synchronous climatic response at the time of the Last Glacial Maximum (LGM) (21 ± 3 ka), with unambiguous cooling recorded in the ocean, and evidence of glaciation in the highlands of tropical New Guinea, southeast Australia and Tasmania. Many terrestrial records suggest drier conditions, but with the timing of inferred snowmelt, and changes to the rainfall/runoff relationships, driving higher river discharge at the LGM. In contrast, the deglaciation is a time of considerable south-east to north-west variation across the region. Warming was underway in all regions by 17 ka. Post-glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north-west of the continent in contrast to the southern latitudes. No evidence for cooling during the Younger Dryas chronozone is evident in the region, but the Antarctic cold reversal clearly occurs south of Australia. The Holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the Holocene, giving way to a weakened monsoon and an increasingly El Niño-dominated ENSO to the present. The influence of ENSO is evident throughout the southeast of Australia, but not the southwest. This climate history provides a template from which to assess the regionality of climate events across Australia and make comparisons beyond our region.14 page(s