Article

Evolution of the river systems of the south-west drainage division, Western Australia

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Abstract

Drainage of the central Yilgarn System is confined within two north-south watersheds, the previously described Central Watershed and the Median Watershed defined here. Runoff today is either intermittent or inactive, but the entire system is gathered to a single outlet through the Median Watershed where it escapes to the Avon. The shape of the catchment with prevalence of north-south alignments, many directed to south coast rivers, suggests that the System originated with southerly drainage. The System is bounded on the south by a watershed parallel to the south coast which formed in the middle to late Cretaceous by marginal uplift of the craton during separation from Antarctica, causing reversal of drainage. There appears to have been a simultaneous down-warp along the line of the present Yilgarn River, the "Chin-Smith lineament". Before uplift the rivers incised canyons into the rifted margin of the continental platform. Subsequently the margin sagged towards the rift forming the Ravensthorpe Ramp and carrying down the valleys as submarine canyons. Along the western part of the south coast there is a secondary axis of uplift, the Stirling Range Axis, 50 km further south. On the eastern side there is evidence for a palaeoriver, the Woolgangie, which has been truncated by the Lefroy-Cowan System. Drainages to the west coast formed in the Mesozoic bounded inland by the Median Watershed. In the early Cretaceous, uplift was associated with continental separation. An extensive canyon was incised at the edge of the rift and later drowned. High sea level prevailed in the Perth Basin to the Late Cretaceous. Regression then promoted rejuvenation of the rivers. The Brockman, Mortlock North Branch and Avon owe their alignments to the Chittering and Jimperding Metamorphic Belts. In the Late Eocene, marginal uplift of the craton by 150-200 m in a belt 80 km wide brought up the Darling Range and caused diversions of drainage. Headwaters of the two Moore Rivers (north and east branches) were diverted to the south, as was the upper Mortlock (north branch). Further down, the Mortlock was relocated some distance east. The combined Avon and Yilgarn Rivers were diverted north, from a westerly course, to join the Mortlock. The Arthur and Beaufort Rivers were cut off from the Collie catchment and diverted to join the Blackwood. Depth of the palaeochannels here and beneath the Avon-Yilgarn afford proof of Darling Range uplift. Monadnocks in the Darling Range which have also been cited as evidence for uplift have been identified and mapped.

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... Although the phylogeography of taxa restricted to freshwater ecosystems in SWA is not as well understood as that of terrestrial taxa, studies of freshwater fishes (Morgan et al., 2014;Galeotti et al., 2015;Buckley et al., 2018) and freshwater crayfishes (Gouws, Stewart & Daniels, 2006;Gouws, Stewart & Daniels, 2010) have also found evidence of separate western and southern lineages, with additional lineages in either the Blackwood basin or Margaret River in the region's south-western corner. Despite SWA's subdued landscape its river basins have long been known to group topographically into distinct west-coast and south-coast systems, with an additional system in the intermediate south west comprising the Blackwood basin (Cope, 1975;Beard, 1999;Bettenay & Mulcahy, 2007; Figure 1). The apparent concordance between regional topography and freshwater phylogeography hints at the existence of distinct subregions of freshwater biodiversity in SWA. ...
... Fieldwork was conducted during the summer of 2019-20 in water bodies (including rivers, creeks and lakes) within the nine coastal F I G U R E 1 Location of south-western Australia on the Australian continent (top right), and major geographical barriers (dashed lines) subdividing the Southwest Drainage Division (based on Beard, 1999) drainage basins comprising the south and south-western parts of the known distribution of W. carteri ( Figure 2; Table S1). This area was targeted because it has been under-represented in previous sampling of the species. ...
... n = sample size, h = haplotype richness, Hd = haplotype diversity (and SD), π = nucleotide diversity (and SD), k = average number of nucleotide differences, S = number of segregating sites and P = number of parsimony informative sites. Note: Margaret River is also included in the Capes basin owing to the inconspicuous ridge surrounding the south coast system (Beard, 1999 (Byrne, 2008;Rix et al., 2015). Interestingly, the more recent origin of WcI during the mid-Pleistocene is presumably associated with a climate shift to cycles of aridification which has also been associated with the isolation and divergence of other taxa in mesic and freshwater refugia (Byrne, 2008;Rix et al., 2015). ...
Article
Intraspecific genetic diversity provides the evolutionary potential to adapt to changing environments and ‘hotspots’ of high intraspecific diversity are recognized as key targets for conservation. In south‐western Australia, intraspecific genetic diversity for mesic taxa is not uniformly distributed. Many species comprise highly divergent lineages with unique haplotypes resulting from contraction to refugia during historical arid cycles. Sampling strategies in studies of the region’s unique and ancient freshwater fauna have often focused on broad distributional range, making it difficult to determine boundaries between lineages and the location of genetic hotspots. This study explored the spatial distribution of intraspecific genetic diversity in the threatened freshwater mussel, Westralunio carteri . Mitochondrial DNA sequences for 164 specimens, sampled from all basins within the distribution of the species, were used to describe lineage boundaries and the location of hotspots, and to reconstruct historical demographics. There was strong evidence for three subregions of genetic diversity based on the largely non‐overlapping distributions of three evolutionarily significant units. Spatial and demographic analyses suggest that these evolutionarily significant units persisted through past arid cycles in separate refugia. The majority of haplotypes were unique to a single location, indicating limited connectivity among populations in recent times. Hotspots were identified throughout the region. Most notably, a significant hotspot in the south‐western corner probably arose through the overlap of lineages in historical refugia. Conservation assessments often focus on the species as a whole, even though sublineages, hotspots and the threats faced are not evenly distributed across the species range. This paper highlights that effective conservation of spatially structured taxa requires targeted management of multiple genetic units. Given the importance of formal taxonomic description for conservation listings, further investigation of the potential for species delimitation within W. carteri is required.
... While it is now understood that large fluvial systems are not essential for the initiation or enlargement of marine canyons (e.g. Western Australia's Albany Canyons: Exon et al., 2005;Greene, 1977;Greene et al., 2002), the close proximity of the shelf-incising Perth Canyon to the Swan River has fuelled sustained interest in the genetic link between them (Bettenay, 1962;Von der Borch, 1968;Playford et al., 1976;Marshall et al., 1989;Shafik, 1991;Commander et al., 2001;Exon et al., 2005;Nicholson et al., 2008;Beard, 1999;Bufarale et al., 2017;Trotter et al., 2019). Post-rift subsidence in the Perth Basin has been punctuated by a number of transgressions and regressions related to relative sea level fluctuations (Fig. 3;Quilty, 1994;Nicholson et al., 2008;Borissova et al., 2015). ...
... The largest and oldest of the palaeo-Swan palaeovalleys (PV1: Fig. 14) incised through Late Cretaceous strata of the open marine deposits of the Coolyena Group, and so is post-Campanian in age. A major regional sea-level regression commenced at 72 Ma ( Fig. 3; Nicholson et al., 2008) and drove channel incisions of up to 200 m inboard of the palaeoshoreline ( Fig. 1; Beard, 1999). While the palaeo-Swan River catchment at that time was much smaller than it is today ( Fig. 1B: Beard, 1999), incised valley dimensions are also sensitive to the magnitude of their catchment discharge (Van Heijst and Postma, 2001a;Mattheus and Rodriguez, 2011;Weill et al., 2014). ...
... A major regional sea-level regression commenced at 72 Ma ( Fig. 3; Nicholson et al., 2008) and drove channel incisions of up to 200 m inboard of the palaeoshoreline ( Fig. 1; Beard, 1999). While the palaeo-Swan River catchment at that time was much smaller than it is today ( Fig. 1B: Beard, 1999), incised valley dimensions are also sensitive to the magnitude of their catchment discharge (Van Heijst and Postma, 2001a;Mattheus and Rodriguez, 2011;Weill et al., 2014). We propose that the wetter conditions of the Late Cretaceous (Beard, 1999;Van de Graaff, 1977) combined with the Swan River's modest-size catchment and the onset of pronounced relative sea level falls that characterise the Late Cretaceous (Quilty, 1994;Nicholson et al., 2008) drove the development of this 400 m deep and nearly 12 km wide subaerial incised valley (PV1) (cf. ...
Article
Perth Canyon is Australia's second largest submarine canyon, and its shelf-incising morphology contrasts with the more prolific slope-confined canyons that typify Australia's passive continental margin. The canyon has a sinuous course that extends 120 km from the shelf break (~180 m depth) to its fan at the foot of the continental slope (~4500 m). Though the canyon initiates only 50 km offshore from a major city, its genesis and geomorphic stability have not been well understood. Bathymetry data acquired in 2015 by the Schmidt Ocean Institute enabled the application of a new two-part seafloor classification approach to objectively map the complexity of the system in unprecedented detail. Part 1 used a semi-automated approach to classify the seafloor bathymetry into morphological categories, and Part 2 defined these units as geomorphological features through the interpretation of sub-bottom and seismic images, sediment samples and acoustic backscatter datasets. The resulting geomorphic map reveals an array of aggradational (cyclic steps and sediment waves), incisional (entrenched canyon floor and nick-points) and mass movement (slump and slab failures) features that for the first time provide detailed insights into the canyon's formative processes. Large faults and the Cretaceous palaeobathymetry appear to have strong influence on the canyon's planform, its depth of incision, and the distribution and types of mass failure that characterise its flanks. These data also reveal the Perth Canyon to be a predominantly relict feature; a large Late Cretaceous infilled incised valley (subaerial) beneath the canyon headwall likely initiated the canyon's development and represents its initial and most active phase. Two more infilled incised valleys are stacked above the first, and demonstrate a progressive decrease in scale, and presumably also canyon activity. Each incised valley represents lowstand incisions of the palaeo-Swan River, and their timing is linked to pronounced Late Cretaceous to Cenozoic sea level regression events, palaeoclimatic change, and onshore catchment enlargement. The disconnection of the modern Perth Canyon from the present day Swan River, and the low rates of sediment accumulation on the adjacent shelf and slope, ensure low rates of sediment supply to the canyon, and only infrequent ignition of turbidity currents. Low rates of sediment supply can similarly account for the entrenched morphology of the modern fan and only minimal headwall movement coincident with seismic events in 2018. However, additional core and bathymetry data for the lower canyon reaches are required to conclusively determine the extent of recent canyon activity.
... The Mesoproterozoic Albany-Fraser Orogen extends along the southern and southeastern margin of Western Australia and consists mainly of orthogneisses and granitic rocks (Condie and Myers, 2010). Paleochannel reconstructions revealed that westward fluvial drainage (e.g., Yilgarn River system, Swan-Avon River, and Blackwood River) had initiated in southwest Australia in the Mesozoic (Von der Borch, 1968;Salama, 1997;Beard, 1999), exporting terrigenous sediments to the southwest Australian margin. It was not until the late Eocene that the uplift of the Darling Range caused a major regional reorganization of the drainage system (Salama, 1997;Beard, 1999). ...
... Paleochannel reconstructions revealed that westward fluvial drainage (e.g., Yilgarn River system, Swan-Avon River, and Blackwood River) had initiated in southwest Australia in the Mesozoic (Von der Borch, 1968;Salama, 1997;Beard, 1999), exporting terrigenous sediments to the southwest Australian margin. It was not until the late Eocene that the uplift of the Darling Range caused a major regional reorganization of the drainage system (Salama, 1997;Beard, 1999). The onshore Perth Basin, which received various riverine sediment inputs from the nearby Yilgarn Craton, Albany-Fraser Orogen, and Leeuwin Block (Salama, 1997;Descourvieres et al., 2011;Olierook et al., 2019), may have also represented an important source of detrital sediment to the Mentelle Basin. ...
... It is likely that this shift was caused by a reorganization of regional catchments associated with an enhanced hydrological cycle. Although the southwest Australian river system is mostly intermittent or inactive today, permanent rivers likely existed during the Cretaceous, delivering terrigenous sediment loads to the ocean margin via westward-flowing river systems (Salama, 1997;Beard, 1999;Hocking et al., 2007). In general, based on these paleochannel reconstruction results, two types of paleodrainage systems are likely to have developed in southwest Australia during the Cretaceous: 1) small and short river systems developed along the coast and draining proximal terranes (i.e., Perth Basin and Leeuwin Block); 2) relatively large catchments (e.g., Yilgarn River, Avon-Swan River, Blackwood River) draining both distant (e.g., Yilgarn Craton) and proximal source regions (Beard, 1999;Hocking et al., 2007). ...
Article
The Oceanic Anoxic Event 2 (OAE 2) represents one of the most profound global environmental disturbances of the Mesozoic Era, which was associated with a positive carbon isotope excursion due to widespread organic carbon burial. However, the character, evolutionary history, and exact driving mechanisms of OAE 2 are still much debated, exacerbated by the lack of records from climate-sensitive southern high latitudes. Here we present a multi-proxy record of a stratigraphically continuous succession spanning the late Cenomanian to early Turonian at the International Ocean Discovery Program Site U1516 in the Mentelle Basin off southwest Australia, which was located at southern high latitudes (~ 60–62°S) during the Late Cretaceous. Sedimentary records at Site U1516 allow the first detailed insights into source-to-sink processes in the Mentelle Basin and associated paleoenvironmental reconstruction in the southern Indian Ocean during OAE 2. Rare earth element abundances and clay-bound neodymium isotopes of the siliciclastic sediment fractions indicate that southwest Australia was the main detrital source of sediment at Site U1516 during OAE 2, with volcanogenic sediments representing only a minor component. A major provenance shift is observed across OAE 2, indicating an increased sediment contribution from distant sources (i.e., Yilgarn Craton and Albany-Fraser Orogen) relative to proximal sources (i.e., Perth Basin and Leeuwin Block) in southwest Australia, interpreted as reflecting a major reorganization of the drainage system due to enhanced fluvial runoff. Based on these findings, we infer that the OAE 2 interval showing the most prominent δ¹³C excursion was associated with an intensification of the hydrological cycle in the high-latitude southern hemisphere, with potential impacts on regional ocean chemistry and marine productivity. In particular, we suggest that enhanced terrigenous input and riverine nutrient export likely played a key role in controlling siliceous productivity at nearby ocean margins. As a consequence, the intense burial of organic matter (i.e., black shale) at Site U1516, which occurred episodically throughout OAE 2, possibly resulted from the combination of enhanced riverine-driven marine productivity and increased burial efficiency associated with the development of anoxic/euxinic bottom water conditions.
... The separation from Antarctica during the Cretaceous (~99-83.5 Ma ago) was accompanied by an uplift of the craton, leading to a change in the drainage direction. There is evidence that rivers in the YC formerly drained towards the south and changed towards the west (Beard, 1999;George et al., 2008 and references therein). Australia is a stable continent due to its intraplate location, but the northward movement of the continent is accompanied by relative high stress shown in three deformation modes: a NE-down and SW-up tilting; a 100 m-scale kink in the lithosphere of 100 km wavelengths; and 10-100 m-scale faulting by 10 km wavelengths (Sandiford, 2007;Sandiford et al., 2009). ...
... Mantle convection, mantledriven dynamic topography and eustasy during the transgression-regression cycles affecting the AFO, changed the sedimentary dynamics of the coastline ( Fig. 12; Sandiford, 2007;Hou et al., 2008 and references therein; Heine et al., 2010;González-Álvarez et al., 2016a). Up to 400 km inland from the present coastline, sediments were deposited due to transgression infill and appear at up to 300 m AHD (Clarke et al., 2003;George et al., 2008), reflecting the continental-scale tilting, despite a reflection of the magnitude of subsequent epeirogenic uplift or marine flooding ( Fig. 12; Beard, 1999;Sandiford, 2007). This uplift in Palaeocene to Early Eocene times was accompanied by the incision of inset-valleys, mostly in the YC and was followed by the deposition of sands in the Late Eocene ( ...
... Composition, structure and behaviour contribute to the configuration or pattern of a landscape. Reconstruction of the evolutionary history of a landscape, including its reworking events, is achieved through analysing relationships between landforms and the basin-to-depocentre architecture (Beard, 1999;George et al., 2008;Fryirs and Brierley, 2013). ...
Technical Report
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Landscape evolution is the result of the interaction of climatic conditions, geological characteristics and sedimentary dynamics through time. In regolith-dominated terrains (RDTs), landscape morphologies and their stratigraphy record the 3D architecture of the overburden. The geochemical relation of the surface, the cover and the basement geology is captured by the landscape stratigraphy. Remote sensing datasets such as Digital Elevation Models (DEMs) can be used to visualise the geomorphological features of the land surface. Combining different surface geometrical features can be used to classify landscape types. Therefore, DEMs can be employed to map landscapes over large geographic areas (e.g., geological province, country or continental scale). In this study we tested the conceptual variability of landscape types within the Albany-Fraser Orogen and south Yilgarn Craton. We used supervised machine learning algorithms based on DEM data and DEM-derived products (e.g., DEM Hillshade and Flatness Map), Google Earth and Bing satellite imageries and field observations. We assessed how landscapes can be classified upon their specific surface geometric features. We generated a map showing six conceptually different landscape types. A total of 3000 km W-E-traverses was conducted in the south Yilgarn Craton and Albany-Fraser Orogen to true the computer-generated landscape map’s geometric surface features, i.e. the six conceptually different landscape types out of machine learning algorithms with field observations. A second traverse was generated, 250 km trending N-S following a palaeovalley, and two W-E traverses (~250 km in sum) crossing the palaeovalley. Google Earth imagery and the recording of stratigraphic sequences associated with the diverse landscape types were also used. The approach implemented in this project can be generalised to assist landscape mapping in RDT by the use of DEM surface geometry. This is a quick and low-cost technique for creating a first-pass landscape type map on a large scale. Landscape mapping can provide a solid reference in mineral exploration for a better understanding of geochemical dispersion of the basement geochemical signatures through cover, by linking stratigraphic units to dispersion processes and surface geometries.
... Surface waters in the Zone of Rejuvenated Drainage are externally drained to the ocean through wellconnected stream networks. Groundwater systems generally share the same divides as the surface water and discharge into the valley floors (Beard, 1999;Mulcahy et al., 1972). ...
... Past the limit of rejuvenation, demarcated by the 'Meckering Line' and 'Jarrahwood Axis' (Cope, 1975;Mulcahy et al., 1972), the Zone of Ancient Drainage has broad valley floors (1-10 km wide) and gently undulating interfluves with low topographic relief. The main valleys are palaeochannels that have very low gradients and are often internally drained, with extensive salt lake systems and thick lacustrine deposits (Beard, 1999;Mulcahy et al., 1972). The groundwater systems, Pleistocene-Pliocene in age (McArthur et al., 1989), in the broad valleys have low hydraulic gradients (0.04-0.17 m per km (Beard, 1999)) with very little lateral movement and discharge is by evaporation from salt lakes. ...
... The main valleys are palaeochannels that have very low gradients and are often internally drained, with extensive salt lake systems and thick lacustrine deposits (Beard, 1999;Mulcahy et al., 1972). The groundwater systems, Pleistocene-Pliocene in age (McArthur et al., 1989), in the broad valleys have low hydraulic gradients (0.04-0.17 m per km (Beard, 1999)) with very little lateral movement and discharge is by evaporation from salt lakes. Due to the low lateral movement, groundwater is compartmentalised and shallow wells (<5 m below ground level) separated by only a few hundred metres can have very different salinities (Mazor and George, 1992). ...
Article
Some of the largest extents of naturally occurring acidic waters are found across southern Australia. The origins of these systems remain poorly understood with many hypotheses for their genesis. Australian government agency groundwater datasets and mapping data (vegetation, geology, regolith and soils) for south-western Australia, unavailable to previous researchers, were statistically analysed to better understand the origins of acidic groundwater and guide additional fieldwork to study the origins of acidic saline groundwater. The groundwater data showed a distinct bimodal distribution in pH; the ‘acid’ population had a median pH of 3.5 and the larger ‘non-acid’ population had a median pH of 6.6. Acidic groundwater became progressively more common further from the coast towards the drier internally drained regions. Acidic groundwater was mostly confined to the lower slopes and valley floors with localised controls on distribution. Paradoxically, subsoil alkalinity within the internally drained inland regions had the strongest correlation with acidic groundwater (r² = 0.85). Vegetation was also a strong predictor of acidic groundwater. Acidic groundwater had the highest occurrence under Eucalyptus woodlands and shrublands that grew on alkaline calcareous soils. Pre-clearing soil data in areas with acidic saline groundwater showed that the upper 1 m of the unsaturated zone had a pH around 8 while the pH at depths greater than 5 m decreased to <4. Based on the observations it is proposed that biogenic formation of calcareous soils occurs in the upper 1 m of the profile, calcium is sourced from the deeper profile where the root biota exchanges calcium for hydrogen ions to maintain charge balance. Iron is mobilised from the upper soil profile and concentrates lower in the profile at depths >1.5 m. There, the iron is reduced around roots and the alkalinity generated by microbial iron reduction is removed by biogenic calcification processes. The iron moves in solution further down the profile following roots where it comes in contact with the oxygenated unsaturated zone matrix and is oxidised generating acid. The resulting acidic recharging solution acidifies the unsaturated zone matrix. Saline groundwater moving through the matrix becomes acidified due to ion exchange or direct recharge. The main chemical processes were modelled in PHREEQC to test the plausibility of the hypothesis and acidic solutions with a pH of 3.8 or lower were obtained.
... Surface waters in the Zone of Rejuvenated Drainage are externally drained to the ocean through well- connected stream networks. Groundwater systems generally share the same divides as the surface water and discharge into the valley floors (Beard, 1999;Mulcahy et al., 1972). ...
... Past the limit of rejuvenation, demarcated by the 'Meckering Line' and 'Jarrahwood Axis' (Cope, 1975;Mulcahy et al., 1972), the Zone of Ancient Drainage has broad valley floors (1-10 km wide) and gently undulating interfluves with low topographic relief. The main valleys are palaeochannels that have very low gra- dients and are often internally drained, with extensive salt lake systems and thick lacustrine deposits (Beard, 1999;Mulcahy et al., 1972). The groundwater systems, Pleistocene-Pliocene in age ( McArthur et al., 1989), in the broad valleys have low hydraulic gradients (0.04-0.17 m per km (Beard, 1999)) with very little lateral movement and discharge is by evap- oration from salt lakes. ...
... The main valleys are palaeochannels that have very low gra- dients and are often internally drained, with extensive salt lake systems and thick lacustrine deposits (Beard, 1999;Mulcahy et al., 1972). The groundwater systems, Pleistocene-Pliocene in age ( McArthur et al., 1989), in the broad valleys have low hydraulic gradients (0.04-0.17 m per km (Beard, 1999)) with very little lateral movement and discharge is by evap- oration from salt lakes. Due to the low lateral movement, ground- water is compartmentalised and shallow wells (<5 m below ground level) separated by only a few hundred metres can have very different salinities ( Mazor and George, 1992). ...
Article
Acid saline groundwater (pH < 4, TDS > 20,000 mg/L) is widespread across southern Australia from Western Australia to Victoria, forming the largest extent of naturally occurring acid waters in the world. The clearing of native vegetation for agriculture in south-western Australia has altered the natural hydrology, reducing evapotranspiration and increasing recharge to groundwater. The consequent rise in watertables has not only resulted in widespread salinisation but also in acidification of surface waters where the groundwater discharge is acidic. On the southern coast of Western Australia, rivers are externally drained and often have acid groundwater in the headwaters and high value biodiversity assets in the lower catchments. The Dalyup River near Esperance, which has become acidified (pH < 4) in some of its upper tributaries, discharges into the Ramsar wetland Lake Gore. To assess the long-term risk of acidification we investigated the hydrological and geochemical processes that control surface water quality. Across the Dalyup River catchment, twelve sites were instrumented with stage height loggers (capacitance probes) and stage height water samplers. Six of the sites had automatic water samplers and pressure transducer stage height loggers. The auto samplers collected daily composite water samples that were analysed for pH and EC. Of these samples, a subset was measured for acidity and alkalinity. A further subset was sent for laboratory analysis. The following investigations focused on the West Dalyup River subcatchment with more intensive sampling (six sites, four with automatic water samplers). Some headwater tributaries were permanently acidic, most notably the West Dalyup, while others became acidic under particular flow regimes. Under high flows, acid water draining from the upper catchment led to acidification in the lower catchment. Some tributaries were alkaline to highly alkaline (pH > 9). The source of alkalinity is unknown. Groundwater was acidic insome parts of the upper catchment and neutral to slightly alkaline in other parts of the catchment. Reducing reactions, particular sulfate reduction, were observed in the hyporheic zone (riparian) sediments. It is hypothesised that catchment disturbance by agriculture (e.g. increased supply of sulfate, nutrients and labile carbon) has facilitated enhanced microbial sulfate reduction and this could potentially be the source of alkalinity. Long-term acidification risk is being modelled.
... This paper is a companion to a recent study of the South-West Drainage Division (Beard 1999). The Monger System was defined and included in that Division by Mulcahy & Bettenay (1972) but was omitted from Beard's recent paper on grounds of space. ...
... Methods followed were the same as for previous papers (Beard 1998(Beard , 1999. Fig 1 was produced by reduction from the latest maps in the National Topographic Map Series scale 1:250 000 (NATMAP, Canberra) and data from the previous papers were drawn upon, particularly for the definition of watersheds. ...
... Both of these rise in a continuation of the north-south ridge which obstructs the outflow of Lake Monger, and the same effect is visible. On the east side of the ridge there are west-flowing drainages aligned with those in both branches of the Moore River, but they have been ponded in Lake Hinds and Lake Ninan and deflected south to join the Mortlock River, part of the Swan-Avon System (Beard 1999). The two branches of the Moore River have been obstructed in turn beyond the Darling Fault by the higher ground of the Dandaragan Plateau. ...
Article
The Moore-Monger Drainage System in the south-west of the Yilgarn Craton is examined in this study. It comprises the catchments of the Salt River rising near Mt Magnet and of the Monger River, both of which find their way into the Yarra Yarra Lakes. The Monger catchment includes both the extensive playas of Lake Monger and Lake Moore. All drainage lines are at low grade and extensively salinised with only intermittent flow. From the Yarra Yarra Lakes to the south there is an intermittent outlet along the line of the Darling Fault which unites with the north branch of the Moore River at Moora and further south with the east branch. These are short active rivers rising not far inland. The combined stream makes its way westwards to the coastal plain and the sea. Drainages located between the Moore-Monger System and the sea, such as the Hill, Arrowsmith, Irwin and Greenough Rivers, are also discussed. These rivers provide numerous examples of apparent disruption of drainage, diversion and reversal attributed to tectonic movements, in particular to upwarping of the cratonic margin in a belt some 70 km wide east of the Darling Fault and affecting the adjacent Perth Basin. This uplift appears gradually to die away towards the north and disappears at Morawa. An upward tilt to the north of the Western Shield has induced rivers to flow southward. This cannot be dated but the marginal uplift of the Yilgarn Craton is concluded to be late Eocene.
... Representative examples of Australian nomenclature include: deep leads (used by the miners and some to the present day, e.g. Holdgate et al. 2006), palaeochannels (Mazzucchelli 2005), palaeodrainage (van de Graaff et al. 1977), inset valleys (De Broekert & Sandiford 2005, palaeodrainage channel (Clarke 1994a, b), and palaeorivers (Beard 1999). Examples of diverse usage for the same features include 'palaeodrainage channel' and 'palaeodrainage' for features on the Yilgarn Craton (Clarke 1994a, b), 'palaeovalley' (Hou 2003a, b) and 'palaeochannel' (Hou et al. (2007a) for features on the Gawler Craton, 'palaeochannel' to describe both incised valleys and channels within a sedimentary succession (Anand and Paine (2002), and 'palaeochannel' and 'palaeodrainage' (Alley et al. 1999). ...
... Palaeovalley refers to an ancient valley that may, or may not, contain palaeochannel sediments. Palaeovalleys are commonly fluvial (van de Graaff et al. 1977, Beard 1999, glacial (Eyles & de Broekert 2001), or tectonic (e.g. the Tamar & Derwent Vallies, Baillie 1989) in origin. Palaeovalley fill include glacial, fluvial (both channel and non-channel facies), lacustrine (Clarke 1994a), marine (Clarke et al. (1996), volcanic (Holdgate et al. 2006), and aeolian in nature, and some or all of these (such as in the Lefroy and Cowan palaeovalleys, Clarke 1994a, b, Clarke et al. 1996 ...
... Palaeorivers are the ancient rivers that once occupied fluvial palaeovalleys (Beard 1999), or which deposited ancient basinal fluvial successions (e.g. Chakrabarti & Mukherjee 1997). ...
Article
Ancient river systems are a prominent feature of the Australian landscape and they host and obscure significant mineral and water resources. To date their nomenclature has been confused and inconsistent. Not all palaeovalleys are formed by rivers; some may be of glacial or tectonic origin. Nor is their fill always fluvial; in may be volcanic glacial, aeolian, or lacustrine. The nomenclature of these features must reflect their actual origin and evolution if their significance is to be properly understood. I propose that 'palaeoriver' be used for the ancient fluvial system responsible for a particular feature, 'palaeodrainage' for the network of palaeorivers, 'palaeochannel' for the channel formed by the palaeorivers, 'palaeochannel deposits' for the sediments that infill the palaeochannels, and 'palaeovalleys' for valleys incised by the palaeorivers. 'Inset valley' should be used to describe a particular palaeovalley profile and not used for palaeovalleys in general. Terms such as 'deep lead', 'prior stream' and 'ancestral river' should not be used, in the interests of consistency and clarity, especially for international audiences.
... We have also avoided, where possible, river profiles affected by dams (Kollmorgen et al., 2007) or rock uplift resulting in river captures and drainage reorganisations. For instance, the Swan/Avon and Moore rivers (profiles a-b, Fig. 1) experienced significant drainage reorganisation as the result of Eocene upwarping that produced a marginal north-south swell in south Western Australia (Beard, 1999;Beard, 2003). Finally, the reactivation of faults may perturb or control river profiles, resulting in localised rather than broad knickzones (N 100 km; Whittaker, 2012;Whittaker and Boulton, 2012). ...
... Based on the analysis of considered river profiles (previous section and Fig. 1), we limit the application of the inverse algorithm of Pritchard et al. (2009) to south Western Australian rivers that consistently display convex profiles with pronounced knickzones. We excluded the Swan/Avon and Moore rivers (profiles a-b, Fig. 1) from this analysis because a Late Eocene drainage reversal has been reported (Beard, 1999) for these rivers. ...
... Based on the pronounced latitudinal asymmetry of Neogene stratigraphy (Fig. 6B) and of the present-day Australian continental shelf, Sandiford (2007) estimated~250-300 m of continentalscale dynamic north-down tilt since the mid-Miocene, at a rate of 15-20 m Myr − 1 . The preservation of a relict, broad-scale (~1000 km), southern tilt in the drainage basins of the Western Plateau (Beard, 1999(Beard, , 2003 further points to long-wavelength dynamic topography. It suggests that prior to Late Eocene surface uplift, the fluvial networks draining south Western Australia were influenced by a depression along the southern margin. ...
... These palaeodrainage system divisions may not have been completely stable over time. For example, Beard (1998 Beard ( , 1999) reconstructed the evolution of the major south-west river systems and unravelled several drainage reversals caused by marginal uplift of the craton during separation from Antarctica during the Cretaceous. Many rivers of the Yilgarn drainage system formerly drained southwards but now converge to a single outlet, Caroline Gap, 229 m a.h.d., in the Median Watershed (Fig. 1) where it escapes westward to the Avon-Swan Rivers (Beard 1999; also figures 5 and 6 in Commander et al. 2001 show the upper reaches of the south-draining Eocene system captured and diverted to the Miocene Avon River to the west). ...
... Pliocene) playa sediments; very limited available palynological data suggest that humid vegetation persisted into the Pliocene in these southern systems (Bint 1981) so playas were not necessarily ubiquitous in all catchments. Rainfall rates along the south coast increase westwards and some valleys in the drier east may have been only partly incised (Beard 1999) and, accordingly, have had relatively low sedimentation rates. This eastern system includes wheatbelt valleys north of the Stirling Ranges in which Commander et al. (2001) document over 60 m of contained Eocene sediments. ...
... Sedimentary fill in the palaeovalleys of the western division has been poorly documented compared with those of the eastern division, although deposits in the Salt River palaeovalley have been studied in detail by Salama (1994 Salama ( , 1997). The Salt River lies in the mid reaches of the Yilgarn River palaeodrainage system whose active lower reaches form the contemporary Avon River and whose inactive headwater is the Yilgarn River palaeodrainage, east of the Caroline Gap (Beard 1999). Up to 80 m of sediments are present in the Salt River palaeodrainage at Yenyening Lakes, comprising sands, clays, and peat. ...
Article
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The Western Australian wheatbelt contains vast areas of agricultural land underlayed by saline and deeply weathered regolith derived from Archaean rocks and recent sediments. The region has been geologically stable since the late Permian, although the Archaean basement sustained some movement during the break-up of Gondwanaland and the northward drift of Australia from Antarctica. During the Early Cretaceous, Eocene and more recently, the wheatbelt region’s weathered mantle has been successively eroded by rivers. The palaeovalleys have been infilled with terrestrial and marine sediments, and subjected to ongoing deep weathering. During the Pliocene and Quaternary the region experienced alternating arid and wetter climates. These cyclic episodes influenced regolith development, affected vegetation species and catchment water balances, and also promoted the accumulation of massive volumes of salt. In more recent times, these salt stores have interacted with vegetation, soils, surface water bodies, and groundwater systems and left a distinctive and pervasive legacy in the landscape. Salinisation was manifest in the wheatbelt from as long ago as 2.8 Ma, concentrating in valley floors as arid and wetter cycles prevailed and while the continent migrated northwards. Today, agricultural development has altered the water balance on 20 Mha of cleared farmland. As a result, salinity is spreading, further degrading 300 000 ha of variably saline landscape that existed before the arrival of Europeans, and affecting an additional 1.1 Mha of formerly arable land. Unchecked by reduced rainfall or human-induced changes to the water balance, salinity may expand even further, potentially affecting 1.7–3.4 Mha of the wheatbelt’s agricultural land and its unique natural resources. This paper reviews the palaeogeography and palaeoclimates of the region and its hydrogeology and examines the nature of its susceptibility to salinisation. It poses questions about the relationship between palaeo-salinity and contemporary salinity, seeking geomorphic evidence to indicate whether salinity is likely to expand beyond extant palaeo-salinity markers. Finally, it considers the likely timeframes involved in salinisation and whether clearing-induced salinity will follow patterns similar to those observed from past saline episodes in the region.
... More recent authors have concentrated on specific aspects of landscape e.g. Twidale (1994); Glassford & Semeniuk (1995); Twidale & Bourne (1998); and Beard (1999) has recently made a comprehensive analysis of the drainage history. ...
... The oldest drainage systems now preserved are likely to be in the zone of ancient drainage (Figure 1) containing the Pingrup, Lockhart and Camm valleys, between the median and the central watersheds, recently recognised by Beard (1998;. The region may have been traversed by palaeoriver systems draining Antarctica when the continents were joined (Figure 4), and Beard (1999) has suggested that these rivers may have originally drained southwards ( Figure 5), following the opening of a seaway between Australia and Antarctica in the Jurassic 150 million years ago (Table 2). It may be significant that these valleys follow the NNW structural trend in the basement rocks. ...
... In the north, uplift of the craton, with tilting to the south, reduced the erosive power of north flowing drainages. Beard (1999) concluded that the Lockhart/Camm/Yilgarn Rivers were captured at Caroline Gap, the one prominent gap in the median watershed. While it is attractive to consider that this expanded catchment may be associated with the cutting of the Perth Canyon, and Kings Park Shale (Salama 1997), the presence of Pliocene sediments in the palaeochannel downstream of Yenyenning ( Figure 6), and the dissection of high level Eocene sediments in the Darling Range suggests a post-Eocene capture. ...
Conference Paper
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Wheatbelt valleys lie in an ancient landscape in which drainage is largely internal and characterised by discontinuous chains of salt lakes. The crystalline rocks, eroded to a plateau maybe some hundreds of millions of years ago, preserve remnants of river systems originating when Australia was joined to Antarctica. These rocks, now deeply weathered beneath the valleys, are incised by old river courses (palaeochannels). The palaeochannels are infilled with up to 60 m of sediments either of Eocene (c 43 million years) or Pliocene (c 5 My) age, and lie within flat bottomed valley floors. The widened out valleys contain up to 20 m of more recent sediments, and soils of colluvial, alluvial, lacustrine and aeolian origin. Digital elevation models derived from the Land Monitor program now give the opportunity to map surface drainage pathways and areas of inundation in detail, and integrate with soils and radiometric data. The flat valley floors, and lack of either surface or subsurface drainage, present a challenge for water management.
... The paleogeographical reconstruction was generated using ODSN (https://www.odsn.de/odsn/services/paleomap/paleomap.html). (Beard, 1999) (Figure 1). In contrast, relatively small river systems (e.g., Blackwood River) flowed through the coastal regions of the Perth Basin and the Leeuwin Block), whereas the Albany-Fraser Orogen was mainly drained by southward-flowing rivers ( Figure 1). ...
... Such change in provenance is further confirmed by the synchronous variation pattern of LREE/HREE ratios at Site U1514, which indicates increased detrital supply from felsic sources (i.e., Yilgran Craton) since the early Eocene (Figure 2a). Large catchments of the Yilgarn River remain almost intermittent or inactive except under climate with exceptionally high rainfall, while small river systems draining the Perth Basin and Leeuwin Block receive comparatively high amounts of precipitation as they lie at the frontal side of the wind belt (Beard, 1999;Chen et al., 2022). Such differences would make sediment discharge from distal catchment regions particularly more sensitive to hydroclimate changes. ...
Article
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Plain Language Summary The Southern Hemisphere (SH) westerlies, which are the dominant atmospheric circulation patterns in the middle latitudes, play a key role in regulating global and regional climate. Currently, the knowledge of past changes in SH westerlies relies mainly on the late Quaternary. Its dynamics over longer timescales, especially under early Cenozoic greenhouse climate states, remain poorly understood. The Mentelle Basin off southwest Australia was located at a more southerly location than at the present day, and was potentially under the influence of SH westerlies. To examine the long‐term hydroclimate changes in southwest Australia during the mid‐late Paleocene to the early Eocene (62–51 Ma), we measured neodymium and hafnium isotopic compositions of fine‐grained detrital sediments from a borehole (IODP Site U1514) drilled in the Mentelle Basin, in addition to clay mineralogy, and elemental abundances. Our results suggest a gradual wetting of southwest Australia since the early Eocene, which we relate to the poleward migration of SH westerlies in response to a reduced latitudinal temperature gradient. An abrupt northward shift of SH westerlies was observed during the short‐lived Middle Paleocene Biotic Event (∼59 Ma), possibly driven by ephemeral growth of the Antarctica ice sheet.
... What criteria should we look for in past records that would indicate a MTC in SWA? We consider three key but interacting features: a) a 3-8-month, summer-autumn drought (Beard, 1999;Groom and Lamont, 2015) with reliable winter rain of 300-900 mm pa (Cowling et al., 2005); b) warm/hot summer-autumn temperatures (daily temperatures may exceed 40°C) with clear skies and low humidity (pan evaporation 1000-2500 mm pa, Lamont and Connell, 1996), and mild winters without snow; and c) intense crown fires at 10-20-year intervals promoted by the hot dry summers Rundel et al., 2016). As currently perceived, the mediterranean-climate region in SWA runs northwards along the west coast from the SW tip of Australia for~1000 km and along the S coast for~800 km and the triangle is completed inland by approximately following the 300-mmpa isohyet (Fig. 1, Lamont and Connell, 1996;Rundel et al., 2016). ...
... Even the rate of annual extension of microlaminae can be used to reconstruct growing conditions (Brachert et al., 2016). Several major rivers that flow, or have flown, into the Indian and Southern Oceans can be traced from the Cretaceous (Beard, 1999) but their historical relationship with coral outcrops is unknown. Thus, the Swan-Avon was rejuvenated in the late Eocene by further uplift of the Darling Range but the age of the coral currently in the vicinity of Rottnest Island near its outlet is not known. ...
... The dominant drainage systems of the wheatbelt are characterised by chains of salt lakes following the courses of Tertiary palaeo-rivers (Beard, 1999;2000). These systems of salt lake chains extend well into the arid interior of Western Australia. ...
... These systems of salt lake chains extend well into the arid interior of Western Australia. Only along the western and southern margins of the ancient Yilgarn Craton has drainage been rejuvenated by marginal uplift during the Cretaceous (Beard, 1999). Drainage east of the Meckering line (Mulchay, 1967) and north of the Ravensthorpe Ramp (Cope, 1975) is effectively internal except in years of extreme rainfall. ...
... The Swan-Avon Basin covers about 124,000 km 2 of south-western Western Australian, draining west-ward to the Indian Ocean near Perth via the Swan River (Fig. 1). The regional geomorphology of the basin consists of mainly broad flat, discontinuous streams in floodplains and numerous lake systems in gently undulating landscapes in the Mortlock, Yilgarn, Salt and Lockhart Rivers (Beard, 1999). These three rivers grade to incised, seasonal streams and rivers in dissected landscapes, receiving moderate to high rainfall in the Swan and Avon Rivers in the west (Beard, 1999). ...
... The regional geomorphology of the basin consists of mainly broad flat, discontinuous streams in floodplains and numerous lake systems in gently undulating landscapes in the Mortlock, Yilgarn, Salt and Lockhart Rivers (Beard, 1999). These three rivers grade to incised, seasonal streams and rivers in dissected landscapes, receiving moderate to high rainfall in the Swan and Avon Rivers in the west (Beard, 1999). ...
Article
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Regional acidification of surface waters is occurring in south-western Australia that is coupled with dryland salinity and acidity carried by rising groundwater. We report on basin-scale influences of acidic saline groundwater discharge on surface water chemistry in the Swan-Avon Basin investigated through 7 years of annual base-flow and lake water quality snapshots. This is linked with analysis of temporal hydrochemistry and discharge at two sites in the basin to assess historic patterns. At least 350 km of major waterways and tributaries in the Swan-Avon Basin were found to exhibit base-flow acidity (pH < 4.5) along with low-level waters in a number of lakes. Acidity appears linked with saline groundwater discharge, contains high concentrations of aluminium, iron and manganese and a range of trace elements (e.g. Pb, Cu, Ni, Zn). There is evidence that acidification has been occurring for at least 30 years and is linked with increased diffuse discharge of saline groundwater in the salinising landscape. However, base-flow acidity in some sub-catchments can be attributed to point discharge from agricultural groundwater drains used to mitigate salinsation of land. Managing acidification of base-flows requires containing diffuse acidification in salinising landscapes and practical options so that landholders can treat point discharge of acidic groundwater from drains. This investigation highlights that the influence of groundwater discharge on stream water quality in salinising landscapes is not limited to salinity and can also include acidification, particularly in deeply weathered regolith. Crown Copyright
... The Permian glaciation (~300-250 Ma) left scars in the Great Plateau, sedimentary packages, and the main drainage patterns (e.g., Ollier, 2001). The rifting of India at ~150 Ma and Antarctica at ~85 Ma (Veevers, 2001) uplifted the craton, driving the incision of the Jurassic (~200-150 Ma) river systems that are present in the landscape today ( Fig. 2), resulting in reversal of the regional drainage (e.g., Beard, 1999). Transgression-regression sedimentary dynamics system dominated large extensions of the southwest for at least the last ~100 My (e.g., Gonzalez-Alvarez et al., 2016). ...
... Most catchments are internally draining with lakes at the terminus, though some can overflow and connect during exceptional rainfall events (Salama, 1997;Commander et al., 2001). This organization of drainage has been in place for around the past 5 million years (Beard, 1999;Commander et al., 2001), creating a highly geologically stable system in which to investigate associations between microbial community diversity and functional capacity. Despite the relative similarity of underlying geology, climate, and landscape history among the Yilgarn lakes, geochemical properties vary widely (Shand and Degens, 2008;Lillicrap and George, 2010). ...
Article
Full-text available
Salt lakes are globally significant microbial habitats, hosting substantial novel microbial diversity and functional capacity. Extremes of salinity and pH both pose major challenges for survival of microbial life in terrestrial and aquatic environments, and are frequently cited as primary influences on microbial diversity across a wide variety of environments. However, few studies have attempted to identify spatial and geochemical contributions to microbial community composition, functional capacity, and environmental tolerances in salt lakes, limiting exploration of novel halophilic and halotolerant microbial species and their potential biotechnological applications. Here, we collected sediment samples from 16 salt lakes at pH values that ranged from pH 4 to 9, distributed across 48,000 km ² of the Archaean Yilgarn Craton in southwestern Australia to identify associations between environmental factors and microbial community composition, and used a high throughput culturing approach to identify the limits of salt and pH tolerance during iron and sulfur oxidation in these microbial communities. Geographical distance between lakes was the primary contributor to variation in microbial community composition, with pH identified as the most important geochemical contributor to variation in microbial community composition. Microbial community composition split into two clear groups by pH: Bacillota dominated microbial communities in acidic saline lakes, whereas Euryarchaeota dominated microbial communities in alkaline saline lakes. Iron oxidation was observed at salinities up to 160 g L –1 NaCl at pH values as low as pH 1.5, and sulfur oxidation was observed at salinities up to 160 g L –1 NaCl between pH values 2–10, more than doubling previously observed tolerances to NaCl salinity amongst cultivable iron and sulfur oxidizers at these extreme pH values. OTU level diversity in the salt lake microbial communities emerged as the major indicator of iron- and sulfur-oxidizing capacity and environmental tolerances to extremes of pH and salinity. Overall, when bioprospecting for novel microbial functional capacity and environmental tolerances, our study supports sampling from remote, previously unexplored, and maximally distant locations, and prioritizing for OTU level diversity rather than present geochemical conditions.
... Approximately 5 tonnes of ironstone gravel soil (0-30 cm) were collected from West Dale (− 32.327233 S 116.509133 E), around 90 km south east of Perth Western Australia. The soil was part of the Eastern Darling Range Zone where there is a moderately to strongly dissected lateritic plateau on granite with eastward-flowing streams in broad shallow valleys, and some surficial Eocene sediments (Beard, 1999). Today's soils are often formed in colluvium derived from lateritic profiles but may also represent in-situ weathered laterite over granite. ...
Article
The > 2 mm fraction of soils is often excluded from laboratory analysis and glasshouse experiments, but is known to influence whole soil physical, chemical and biological properties. The historical focus on the < 2 mm fraction has led to a knowledge gap in analytical procedures and flow-on effect for agronomic response and advice when the > 2 mm fraction is present, especially when it is porous and chemically reactive. An ironstone gravel soil (Endopetric Pisoplinthic Plinthosol (Arenic)) from south west Western Australia was separated into < 2, 2–4, 4–6, 6–8 and 8–10 mm fractions. Physical analysis included specific surface area (SSA), optical mineralogy, XRD and SEM. Chemical analysis included phosphorus (P) sorption, P retention index (PRI), P buffering index (PBI) and sodium bicarbonate extractable P (Cowell P) on intact and ground samples, and intact mixtures of the < 2 mm and > 2 mm fractions. Δ NaF pH was used as a surrogate P retention measure on intact mixtures of the < 2 mm and > 2 mm fractions. P adsorbed onto the > 2 mm fraction can be measured as Colwell P, suggesting this fraction can provide P to plants. Colwell P determined on ground samples was correlated 1:1 with Colwell P on intact counterparts. Grinding of samples resulted in large increases in PRI and PBI, and is not a supported sample preparation, neither is the use of end over end shakers due to surface abrasion of the > 2 mm fraction increasing P sorption, however the use of Δ NaF pH as a surrogate measure of P sorption offers some potential. Phosphorus adsorption decreased with increasing particle size but adsorption by the > 2 mm fraction is likely significant in the context of an entire unsieved soil and was influenced by SSA. The > 2 mm fraction had higher SSA than their physical size would imply, possibly influenced by the thickness and mineralogy of the exterior coating (rind). Our results show that the > 2 mm fraction contains reactive surfaces that can contribute to the nutrient holding capacity and plant available P of soils.
... River drainage evolution can be driven by different mechanisms, mainly including (1) tectonic or morphotectonic controls (e.g., Beard, 1999;Yin and Yu, 2000;Zelilidis, 2000;Moore and Larkin, 2001;Maroukian et al., 2008;Galloway and Whiteaker, 2011) and (2) climatic factors (Lemmen et al., 1994;Bridgland and d'Olier, 1995;Roddaz et al., 2005). Although Taiwan is located in a tectonically active setting and earthquake frequently occurs (Huang et al., 1997;Dadson et al., 2003), there is no evidence of a significant shift of the tectonic regimes (commonly with a million-year timescale) since the last glaciation. ...
Article
As an important component in East Asia sediment source-to-sink systems, small mountainous rivers in Taiwan deliver disproportionately large amounts of sediments to oceans. Although the modern fluvial sediment transport processes, discharge fluxes and sediment compositions have been well investigated, the drainage evolution of these mountainous rivers remains understudied and sediment fluxes are expected to vary greatly in glacial-interglacial cycles due to the tremendous climatic fluctuations. To define how the drainage of Taiwan mountainous rivers has evolved since the last glaciation, we target a sediment core (98 m in length) from the Zhuoshui River delta, western Taiwan and use sediment petrography, heavy mineral analysis, detrital zircon UPb geochronology and clay mineralogy to investigate provenance variations and river basin evolution since 60 ka. Sediments of the last glaciation show comparatively high illite crystallinity index values, low metasedimentary lithic fragment and stable heavy mineral contents and similar detrital zircon UPb ages with downstream signatures, indicating prominent sediment contributions from the Coastal Plain and Western Foothills regions (elevation <1 km) during the glaciation. However, characteristics of the deglacial and Holocene sediments indicate high contributions from the higher Hsueshan Range and Central Range regions (elevation >1 km). We suggest that headward extension and drainage capture since the deglaciation, which was most likely due to the increasing monsoon rainfall, account for the provenance variations in the discharged sediments. This implies a climate-driven drainage reorganization of the small mountainous rivers in Taiwan since the last glaciation. Our findings highlight the previously-overlooked, variable provenance information from Taiwan in glacial-interglacial cycles, and the dynamic source signatures are important to East Asia sediment source-to-sink studies.
... Rivers in the southern part of Western Australia record some 200 m of surface uplift since the mid-Eocene due to a migration of downwelling away from . The ~200 m uplift has resulted in river reversals; the west-and south-flowing rivers changed course northwards due to the uplift of the Darling Range, and the southwest and south coasts became watersheds (Beard 1999), isolating and thereby preserving the southwest temperate biome from aridification. ...
Chapter
We discuss the Australides, the orogenic belt that covers eastern Australia, New Zealand, East and West Antarctica, the Cape region of Africa, and South America, and summarize its tectonic history since the Neoproterozoic. A biotic analysis using palaeodistributional data is used to determine relationships between areas within the Australides. We integrate the palaeobiogeographic (phylogenetic) and tectonic histories in order to establish the extent in space and time of any Weddellian Province, and undertake an analysis of phylogenetic data (cladograms) to determine whether area relationships are driven by tectonostratigraphic terranes or by cratons and cratonic basins.
... Rivers in the southern part of Western Australia record some 200 m of surface uplift since the mid-Eocene due to a migration of downwelling away from . The ~200 m uplift has resulted in river reversals; the west-and south-flowing rivers changed course northwards due to the uplift of the Darling Range, and the southwest and south coasts became watersheds (Beard 1999), isolating and thereby preserving the southwest temperate biome from aridification. ...
Chapter
We investigate some exemplar regions where the integration of neotectonics and dynamic topography had created unique biogeographic areas, namely, transition zones. We also term two new concepts, Marginal Plate Biotectonics and Intra-plate Biotectonics, to distinguish between different types of tectonic and biogeographic interactions. A preliminary analysis reveals that transitions zones along tectonic margins (subduction, transverse) share greater similarity to each other than they do with those found within plates. We also propose a case for biotectonic extinction and discuss the future of biotectonics.
... Rivers in the southern part of Western Australia record some 200 m of surface uplift since the mid-Eocene due to a migration of downwelling away from . The ~200 m uplift has resulted in river reversals; the west-and south-flowing rivers changed course northwards due to the uplift of the Darling Range, and the southwest and south coasts became watersheds (Beard 1999), isolating and thereby preserving the southwest temperate biome from aridification. ...
Chapter
Australia is the flattest continent on Earth and has a wide range of different landforms, making it an ideal place to investigate the impact of neotectonics (continental tilting and dynamic topography) on bioregionalisation. It is highly likely that continental tilting and dynamic uplift together have driven the biogeography of Australia since the Palaeogene.
... Rivers in the southern part of Western Australia record some 200 m of surface uplift since the mid-Eocene due to a migration of downwelling away from . The ~200 m uplift has resulted in river reversals; the west-and south-flowing rivers changed course northwards due to the uplift of the Darling Range, and the southwest and south coasts became watersheds (Beard 1999), isolating and thereby preserving the southwest temperate biome from aridification. ...
Article
Tectonic plates are constantly moving, either crashing into one another creating a mosaic of mountains and shallow seas, or tearing apart and isolating large swathes of land. In both cases plate tectonics separates populations leading to the evolution of biota. Tectonics is also responsible for the destruction life, for instance when large coral reefs or shallow seas are compressed to form mountain peaks. Could recent research into these processes provide enough evidence to show that tectonics may be the ultimate driver of life on Earth? Our book delves into the current research in tectonics, particularly neotectonics, and its impact on rapid changes on biogeographical classification, also known as bioregionalisation. We also introduce a new term biotectonics that studies the impact of tectonics on biogeoregionalisation. The question we ask is how tectonics directly influences the distribution of biota in four case studies: the Mesozic and early Palaeogene Australides, which spans the Proto-Pacific coast of the South America, Antaractica and Australiasia; and the Neogene of Australia. To conclude we examine the role of neotectonics on tranistion zones and the Amazon Basin and make a case for biotectonic extinction.
... Rivers in the southern part of Western Australia record some 200 m of surface uplift since the mid-Eocene due to a migration of downwelling away from . The ~200 m uplift has resulted in river reversals; the west-and south-flowing rivers changed course northwards due to the uplift of the Darling Range, and the southwest and south coasts became watersheds (Beard 1999), isolating and thereby preserving the southwest temperate biome from aridification. ...
Chapter
Neotectonics has undergone incredible development since Vladimir Obruchev proposed the term in 1948. With the discovery of mid-oceanic ridges, subduction, mantle flow, and dynamic topography, neotectonics has become the forefront of tectonic research. This chapter attempts to unite two fields, neotectonics and bioregionalisation, the latter being a result of the former.
... Gouws et al., 2006Gouws et al., , 2010, and is likely a consequence of geological division of the south-west coast drainage division during the Eocene. Beard (1999) shows that geological formation appeared to create two distinct watersheds, or drainage subdivisions in south-western Australia: one on the south coast to the south of the ''Jarrahwood Axis'' and one on the west coast, to the west of the Yilgarn Craton and the Darling Scarp. ...
Article
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South-western Australia is isolated from other forested regions of Australia by desert and bounded on southern and western sides by the Southern and Indian Oceans, respectively, with Westralunio carteri (Iredale, 1934) as the sole endemic freshwater mussel. Its conservation status is vulnerable. This species has a history of nomenclatural change and its systematic placement and population genetic history are largely unknown. We sampled 46 individuals from 13 sites across W. carteri’s distribution and sequenced two mitochondrial genes (16S rDNA and cytochrome c oxidase subunit I) and one nuclear gene (28S rDNA). The mitochondrial haplotype networks and COI phylogenies revealed three evolutionarily significant units (ESUs): “W. carteri” I including the west coast populations, “W. carteri” II from the south and south-eastern range, and “W. carteri” III only occurring in the south-western tip of Australia. Four species delimitation methods identified two molecular operational taxonomic units supporting two distinct species (“W. carteri” I and “W. carteri” II + III). Phylogeographic patterns revealed herein confirm the historical separation of Western and Southern paleo-basins, also highlighting the isolation of the southwestern extremity of the region. This underlines the need for taxonomic revision and will require a reevaluation of W. carteri’s conservation status.
... The morphology and flow of the river also changes from a shallow wide diffuse river bed with salt pans along its length, to a narrower deeper 'rejuvenated' river channel. Yilgarn craton rivers to the north and south of the Mortlock river show similar changes in morphology and direction, recognised as a major drainage change within the Swan-Avon System (Jutson, 1934;Mulcahy, 1967) and attributed to Eocene uplift along the Darling Fault (Beard, 1999;Jakica et al., 2011;Salama, 1997). Clark and Edwards (2018) explore the relationship between the historic rupture, potential prior seismic offset of the Mortlock River, bedrock/geophysical controls on river morphology/direction, and larger scale drainage patterns. ...
Preprint
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The 14th October 1968 MW 6.6 Meckering earthquake surface rupture is comprised of a main 37 km long concave Meckering scarp (with a 1.5 km wide dextral step-over along the Burges en-echelon rupture complex) and a minor 9 km long rupture on the Meckering scarp foot-wall (the Splinter scarp, also with a 1.5 km dextral step-over). We recommend a total surface rupture length of 44.4 km for implementation into magnitude-length scaling relationships based on a reassessment of primary rupture lengths. High resolution aeromagnetic data show the arcuate limbs of the Meckering scarp are controlled by basement structures, with supportive evidence from surface outcrops. No definitive evidence exists to support any rupture along these structures between their Archean - Proterozoic formation and Tertiary to Quaternary sedimentation. The rupture is characterised by near-surface bedrock along most of its length, and available trenching shows only the historical offsets. We find that available seismological, geological and surface rupture data support a model in which rupture intiates on the Splinter fault as a sub-event 3.5 sec before the mainshock, propagating to the surface and downwards to an intersection with the main Meckering fault at 2.8 km depth (consistent with centroid depth estimates of 2.3 – 3.0 km). Rupture then propagates bi-laterally from the fault intersection across the Meckering faults to produce the mainshock. Further modelling would be required to test the strength of this model. This earthquake is one of the most structurally complex (as proxied by the number of discrete faults) for its magnitude, as evidenced by comparison with a global compilation.
... Generally, passive treatment systems based on vertical flow are preferable to horizontal flow systems as they are more efficient, present smaller surface areas for evaporation and are less likely to suffer from preferential flow (Younger (Younger et al. 2002). However, hydraulic gradients in the Western Australian wheatbelt are in the order of 10-30 cm per 1000 m (Beard 1999) so that there is insufficient hydraulic head for RAPS or OLC. High evaporation in summer is likely to cause low to stagnant flow and high iron and aluminium concentrations, which would affect the efficiency of slag or limestone leach beds due to armouring with iron and aluminium (oxy) hydroxides. ...
Technical Report
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As our natural resources come under increasing pressure, such that the necessity to create secure sources of energy, water and food, with reduced environmental impacts and long term sustainability becomes paramount, alternative adaptive integrated management frameworks for these resources are required. This report addresses some of the challenges, perception and opportunities associated with inland desalination, brine management, agricultural drainage and water resources. While many small and large scale desalination plants have been installed globally and the number is on the increase (Stedman 2014), there is pressure to ensure that these plants are multifaceted in their benefits, while being sustainable in the longer term (Porath et al. 2014). For inland desalination plants, mining and agricultural drainage there are limited options for disposal, and although they tend to be smaller, the discharge of large quantities of brine is normally into dry or arid landscapes. The options and economics for brine management is limited, particularly for remote locations, such that innovation in technologies and business models are required. The discharge of brine (or saline groundwater ) and associated components into the environment, particularly the inland areas of Australia, creates challenging environmental, disposal and regulatory issues when implementing a drainage plan, constructing a desalination plant or evaporative disposal basin. All require innovative business operational and economic models, with significant government support (in some cases) that is either financially or regulatory in nature, with one of the main constraints limiting desalination for agriculture being related to water, both its production and distribution costs. However, in the last three decades, salinity, and in particular groundwater salinity, in inland environments, is being increasingly viewed as a utilisable resource, if associated technological, economic and environmental considerations can be resolved. This report addresses some of the challenges, perception and opportunities associated with inland desalination, brine management, agricultural drainage and water resources.
... The potential for the Albany-Fraser Orogen to have acted as a physical barrier to sedimentation from the Yilgarn Craton towards the study region may be significant through much of the Proterozoic history of the Officer Basin. However, comparisons with Palaeozoic palaeovalleys in the Northern Territory and mapping of Yilgarn Craton palaeovalleys and their hosted sediments demonstrates a protracted (at least Mesozoic) history of drainage (Bell et al., 2012;de Broekert and Sandiford, 2005) that would have facilitated detrital grain transfer to the Madura Shelf even with reported tectonically induced reversals and adjustments to drainage patterns during separation of Australia and Antarctica (Beard, 1999;Hou et al., 2008). Therefore, the paucity of Archean grains supports hypotheses (Cawood and Nemchin, 2000;Sircombe and Freeman, 1999) of a covered or denuded Yilgarn Craton landscape lacking sufficient topography to generate a significant supply of detrital zircon grains from at least the Mesozoic. ...
Article
Sedimentary rocks along the southern margin of Australia host an important record of the break-up history of east Gondwana, as well as fragments of a deeper geological history, which collectively help inform the geological evolution of a vast and largely underexplored region. New drilling through Cenozoic cover has allowed examination of the Cretaceous rift-related Madura Shelf sequence (Bight Basin), and identification of two new stratigraphic units beneath the shelf; the possibly Proterozoic Shanes Dam Conglomerate and the interpreted Palaeozoic southern Officer Basin unit, the Decoration Sandstone. Recognition of these new units indicates an earlier basinal history than previously known. Lithostratigraphy of the new drillcore has been integrated with that published from onshore and offshore cores to present isopach maps of sedimentary cover on the Madura Shelf. New palynological data demonstrate progression from more localised freshwater-brackish fluvio-lacustrine clastics in the early Cretaceous (Foraminisporis wonthaggiensis – Valanginian to Barremian) to widespread topography-blanketing, fully marine, glauconitic mudrocks in the mid Cretaceous (Endoceratium ludbrookiae – Albian). Geochronology and Hf-isotope geochemistry show detrital zircon populations from the Madura Shelf are comparable to those from the southern Officer Basin, as well as Cenozoic shoreline and palaeovalley sediments in the region. The detrital zircon population from the Shanes Dam Conglomerate is defined by a unimodal ~1400 Ma peak, which correlates with directly underlying crystalline basement of the Madura Province. Peak ages of ~1150 Ma and ~1650 Ma dominate the age spectra of all other samples, indicating a stable sediment reservoir through much of the Phanerozoic, with sediments largely sourced from the Albany-Fraser Orogen and Musgrave Province (directly and via multiple recycling events). The Madura Shelf detrital zircon population differs from published data for the Upper Cretaceous Ceduna Delta to the east, indicating significant differences in sediment provenance and routing between the Ceduna Sub-basin and central Bight Basin.
... The resulting subdued landscape of the Darling Plateau is mantled by Tertiary-Quaternary laterites and sand plains on the upland, and duplex soils in the broad valleys. The drainage systems to the west of the Meckering line have been rejuvenated due to minor recent uplift along the western edge of the plateau, while to the east drainage is sluggish, largely consisting of series of salt lakes following the Tertiary paleodrainage lines (Mulcahy, 1967;McArthur, 1993;Beard, 1999Beard, ,2000. The Yilgarn Craton is flanked to the west and south by sedimentary basins that presently form narrow coastal plains. ...
... A comprehensive study of the geomorphology, geology, and paleohydrology of the Salt River system by Salama (1997), within the context of the regional development of the drainage system (Beard, 1999(Beard, , 2000, noted that the Salt River system connects the saline playas of the Yilgarn catchment in the eastern ancient zone with the rejuvenated Avon-Swan system in the west and has probably occupied the same course since the early Tertiary. At that time, the uplift of the Yilgarn Craton and the formation of the Darling Scarp dammed the river and caused the formation of a large inland lake. ...
Article
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The term “playa” or “pan” applies to individual arid zone basins of varying size and origin that are subject to ephemeral surface water flows (Shaw and Thomas, 1989) such that lakes may occur within playas as permanent or ephemeral features. Playas in Australia are often geologically young (Quaternary) features developed in arid environments and are often dry due to evaporation (Boggs et al., 2006). Although playas are a response to tectonics, climate change, and eolian and fluvial processes, the majority of the scientific literature considers either their origin within a regional context, or the development dynamics of individual playas (e.g., Bettenay, 1962). However, where playas are developed within paleodrainage channels, they may exist as isolated features, but more often they exhibit a degree of hydrological interconnectivity with other playas to form “playa chains” such that the development history of an individual playa cannot be addressedwithout consideration of its neighbors.
... On the Yilgarn Craton, the regolith profile is typically 30-50m of gritty clay saprolite formed by in situ weathering of the crystalline basement rock. The weathered profile is occasionally covered by 10-30m of mixed sediments in sheets or palaeochannels (Beard 1999). The western edge of the Yilgarn Craton is defined by the Darling Fault, which extends some 700km north-south through the entire region. ...
... Also, the western zone has a rejuvenated drainage system that flows westwards while the eastern zone's ancient drainage system comprises chains of salt lakes and follows Tertiary paleodrainage lines that are orientated northwards and/or eastwards (e.g. Beard, 1999;McArthur, 1993). These broad landscape differences more or less correspond to the four dendrogram groups analysed; deductive studies such as this do not eliminate alternative hypotheses (Oksanen, 2001). ...
Article
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Three hundred and four quadrats each of ca. 1 ha were chosen to represent the geographical extent and diversity of uncleared terrestrial environments in a 205 000 km2 area known as the Western Australian agricultural zone. This study area occupies 75% of south-western Australia, one of the world’s 25 bodiversity hotspots under threat. Seventy-four percent of the study area has been cleared for agriculture and 4% is now salinised. Its subdued landscape comprises isolated remnants of bushland embedded in a mosaic of wheatfields. Six phylogenetic groups were sampled, and a total of 2071 plant and 807 small ground-dwelling animal species were recorded from the quadrats. An average of 3.1 species per quadrat were recorded from only a single quadrat, but they were not randomly arrayed. The richest assemblages of singletons were around the periphery of the study area, where biogeographical edgeeffects would be expected. A total of 1922 species remained after the singletons were removed from the data set, an average of 71.1 per quadrat (s.d. = 22.8). They comprised 1335 plants, 472 spiders, 66 reptiles, 21 frogs, 11 mammals and 17 scorpions. Seventeen assemblages were distinguished when the 1922 species were classified according to similarities in their presence or absence at the 304 quadrats. Each assemblage could be characterised in terms of the Australiawide habitat preferences (where known) of its component species. Also, separate quadrat similarity matrices were generated for the four main types of organism sampled (plants, spiders, scorpions and herpetofauna) and for 100 random matrices. These were output as linear similarity vectors so that the differences in their biodiversity patterns could be quantified as a single matrix of correlation coefficients. Analyses revealed that: 1. Geographical patterns in assemblage species composition were correlated with processes operating at both biogeographical and local (ecological) scales: the compositional structure of each assemblage was related to a different set of climatic plus soil and/or landform attributes. Since these attribute-sets were consistent with the assemblages’ extrinsic characterisations, they are unlikely to be artefacts of quadrat positioning or study area extent and were treated as realised environmental niches. 2. Broad biogeographical patterns in biodiversity showed strong relationships with temperature and rainfall gradients, especially ‘warmest period mean temperature’ and ‘precipitation seasonality’. 3. The centres of diversity of the 17 assemblages revealed by our analysis were found to cross various biogeographical boundaries currently recognised in the study area, both regional and sub-regional. Because they provide a view of geography from the perspective of a wide range of organisms, these ‘centres’ provide a tactical framework for managing the effect of salinity on biodiversity. 4. The ecologically different clades (plants, spiders, scorpions and herpetofauna) each had a distinct influence on the biodiversity model; cross-taxon congruence levels were low. If a bio-regionalisation based on only one or two types of organism was used as a framework for conservation activities in the study area it would produce distorted outcomes. 5. There was an inverse relationship between species richness and soil salinity for the eight assemblages that occur on, or extend onto, landforms affected by rising saline ground-water. Six assemblages are dependent on surface-types low in the landscape, and their uncleared remnants need to be assessed against hydrological models so that priority land parcels can be identified. Collectively, these six assemblages encompass populations of 50.1% of the 1922 species included in our analysis. The compositional loss associated with secondary salinisation affects all biodiversity components surveyed: plants, vertebrates, spiders and scorpions.
... Sediment sources -The location of the main source was decided from the literature. The minor sources from the Yilgarn Block (Beard 1999) were derived partly from the location of palaeo-river valleys related to the present-day rivers. The sources from Greater India were added after several simulation runs showed a sediment deficiency to the western side of the basin. ...
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Several geothermal projects in the Perth Metropolitan Area, Western Australia, have already demonstrated the geothermal potential of the area for aquifers down to 1 km depth. The Western Australian Geothermal Centre of Excellence (WAGCoE) was tasked with assessing the potential of deeper aquifers. Members of WAGCoE, in collaboration with CSIRO, investigated the use of stratigraphic forward modelling (SFM) techniques combined with geothermal reservoir definition to identify potential geothermal reservoirs in locations where data are sparse. The major aquifer and low-temperature geothermal target in the Perth Basin, the Yarragadee Aquifer, provides a major portion of Perth's drinking water. Although the shallow part of the Yarragadee Aquifer has been well studied by hydrogeologists, the deeper part is still poorly characterized. Using the stratigraphic forward modelling package Sedsim, the sedimentation of the Yarragadee Formation was simulated over a period of 15.8 Ma. The simulation was calibrated against sparse seismic surveys, petroleum wells and core data. The final simulation volume was uplifted and eroded to the current state of the Yarragadee Formation, providing estimates of facies, grain size and porosity distributions for the entire formation. Once the characterization of the Yarragadee Formation was achieved, the identification of geothermal reservoirs required investigating the suitability of the subsurface to deliver the energy required for a given geothermal application. Based on simple assumptions such as constant thermal conductivity, uniform geothermal gradient, and using pre-defined geothermal production design settings such as flow rate and maximum pressure drop, parameters such as the reservoir temperature and the reservoir producible power are evaluated. As different geothermal applications have different subsurface requirements, reservoirs are individually investigated for a specific geothermal applications. This methodology has been developed to allow rapid investigation of the local geothermal potential while changing the surface geothermal application requirements.
... Glaciation of this part of Gondwana may have caused the erosion and created a relatively flat landscape with river systems characterised by low gradients. The current palaeodrainage pattern in the Southwest region had developed throughout the Yilgarn by the late Cretaceous, 65 million years ago (Beard, 1999). ...
Technical Report
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Human-induced salinisation of the Australian continent’s land and water has been occurring for last the 100 years, with some early reported incidents occurring in the Western Australian Wheatbelt (Bleazby, 1917; Wood, 1924). It is well documented that natural salinisation of parts of the Australian continent is due to climate throughout the geological record, (Bowler, 1990) as is demonstrated by the salt lakes of southern Australia. It is also well documented, however, that the recent increase in land and surface water salinisation occurred because native vegetation was cleared (Peck et al 1973). The changes in land use have altered the natural water balance, and increased recharge by more than one order of magnitude (Peck 1978; Allison and Hughes, 1978). The increased recharge rates have caused a substantial rise in groundwater levels, resulting in land salinisation and seepage into the surface water systems. Toolibin Lake and its catchment (48,000 hectares) are affected by dry land salinity, similar to most of the valley floors and low-lying areas (McFarlane, 1989). The salinity of Toolibin Lake has increased, due to the rise in salinity of the North Arthur River (that drains approximately 90% of the catchment), and the level rise of saline water under the lake. These factors have resulted in a deterioration of the lake’s ecosystem (George and Dogramaci, 2000). Toolibin Lake is one of a chain of lakes occupying a palaeodrainage valley that forms part of the Northern Arthur River System (Fig. 1). Toolibin Lake (and the surrounding reserves) is an important breeding habitat for native flora and fauna and has been listed under the Ramsar Convention as a Wetland of International Importance. Although there have been numerous regional and catchment-scale investigations into the groundwater dynamics and surface-water hydrology, few studies to date have addressed the interaction of surface and groundwater, and its ultimate impact on the ecology of Toolibin Lake. The objectives of this review is to collate available data on the Toolibin catchment, describe groundwater dynamics and related interaction with surface water, and present a model of the catchment in the light of recent investigations. In addition, a salt and water balance of Toolibin Lake has been prepared and modelling undertaken to review the impact of several management options. The hydrological processes associated with dry land salinity and the salinisation of surface water are described in this report using data compiled over the last 20 years. A description of the landscape’s evolution and its impact on the development of dry land salinity is presented. The effects of treatment options to control and reduce the impact of salinity are explained. Possible variations in salt load and associated stream flow changes are estimated for a range of treatments.
... The reversed Cowan River flowed into the Southern Ocean or a precursor rift (Fig. 4). An overview of a much larger area of south-western Western Australia is provided by Beard (1999), who documents many great changes, too complex to summarize here. ...
Article
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Landscape evolution of Australia is on the same time scale as global tectonics and biological evolution. In places, actual landforms and deep weathering products are hundreds of millions of years old. Much of Australia has a landscape resulting from stripping of weathered rock after an earlier period of very deep weathering. Other regions have sequential landforms that provide a natural laboratory where we can work out the biogeochemistry of the past. Landforms and regolith reveal the long evolution of groundwater in Australia. Lateral movement of groundwater is of paramount importance. The effects of past climates are stored in the landscape. They show that the present is not the key to the past, and former environments must be worked out from consistent internal evidence rather than the application of models based on present-day conditions. Inorganic chemistry alone is inadequate to explain many earth materials, and biology, especially microbiology, has a very significant role. Recent and present-day processes also affect the landscape, and it cannot be assumed that because the landscape and regolith are old the soils are old. Many regions have a complex regolith cover that shows modern processes working on inherited materials.
... This complexity can be reduced, in essence, to a sandstone aquifer with a K sat ~ 290 times higher than the overlying claystone aquiclude (P = 0.0005 for the Student's t-test for the significance of the mean difference) (Clarke et al. 2000). Beard (1999) described some recent ideas on the mode of deposition of these sediments, but their effect on salinity is caused by the materials of which they are composed, not how they formed. Hingston and Gailitis (1976) showed that the accretion rate of salt from oceanic aerosols (primarily sodium and chloride ions) in the wheatbelt of Western Australia was 100-250 kg/ha.year in high rainfall coastal areas, falling to 10-20 kg/ha.year ...
Article
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Replacement of deep-rooted, perennial native vegetation with shallow-rooted, annual agricultural plants has resulted in increased recharge causing shallow saline water tables leading to dryland salinity and loss of agricultural production. Restoring the vegetation by regeneration or replanting lowers water levels locally but field evidence and computer modelling suggests this needs to be widespread for regional effects, which conflicts with the future of conventional agriculture. Alley farming allows agriculture to be continued in the bays between the rows, but needs as much perennial, preferably deep-rooted, vegetation as possible in the bays to achieve the required recharge reductions. Where the asset to be preserved is valuable and a means of safe saline effluent disposal exists, pumps and drains will be part of any salinity management system, but where these conditions are not met they will be of limited use on an economic basis. To limit the spread of dryland salinity substantial change in farming systems is required and farmers need assurance that the recommended strategies will have the desired effect. Computer modelling is the only timely way to do this. An operationally simple 1-dimensional model already exists, and a 2-dimensional one is under development and testing. Three-dimensional modelling is also probably required to support strategic, intensive interventions. computer modelling, revegetation, engineering, perennial.
... However, vertical flow systems require more than two metres hydraulic head to drive flow (PIRAMID Consortium, 2003). This makes them unsuitable for the Western Australian wheatbelt, where hydraulic gradients are in the order of 10e30 cm per 1000 m (Beard, 1999). Given the constraints of cost and low hydraulic head, horizontal flow compost wetlands or bioreactors would be the most suitable passive treatment technology. ...
Article
Extremely acidic and saline groundwater occurs naturally in south-western Australia. Discharge of this water to surface waters has increased following extensive clearing of native vegetation for agriculture and is likely to have negative environmental impacts. The use of passive treatment systems to manage the acidic discharge and its impacts is complicated by the region's semi-arid climate with hot dry summers and resulting periods of no flow. This study evaluates the performance of a pilot-scale compost bioreactor treating extremely acidic and saline drainage under semi-arid climatic conditions over a period of 2.5 years. The bioreactor's substrate consisted of municipal waste organics (MWO) mixed with 10 wt% recycled limestone. After the start-up phase the compost bioreactor raised the pH from ≤3.7 to ≥7 and produced net alkaline outflow for 126 days. The bioreactor removed up to 28 g/m(2)/d CaCO3 equivalent of acidity and acidity removal was found to be load dependent during the first and third year. Extended drying over summer combined with high salinity caused the formation of a salt-clay surface layer on top of the substrate, which was both beneficial and detrimental for bioreactor performance. The surface layer prevented the dehydration of the substrate and ensured it remained waterlogged when the water level in the bioreactor fell below the substrate surface in summer. However, when flow resumed the salt-clay layer acted as a barrier between the water and substrate decreasing performance efficiency. Performance increased again when the surface layer was broken up indicating that the negative climatic impacts can be managed. Based on substrate analysis after 1.5 years of operation, limestone dissolution was found to be the dominant acidity removal process contributing up to 78-91% of alkalinity generation, while bacterial sulfate reduction produced at least 9-22% of the total alkalinity. The substrate might last up to five years before the limestone is exhausted and would need to be replenished. The MWO substrate was found to release metals (Zn, Cu, Pb, Ni and Cr) and cannot be recommended for use in passive treatment systems unless the risk of metal release is addressed.
... These sequences are highly variable in vertical and spatial distribution. Beard (1999) recently deliberated on the history and flow direction of wheatbelt palaeodrainages. Building on earlier work and together with experimental data obtained from drilling at many places (e.g. ...
Article
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Wheatbelt valleys contain evidence of a long history of hydrologic and climatic change. In particular they contain ancient palaeodrainage systems comprising large volumes of saline groundwater. Prior to clearing, these palaeodrainages discharged small amounts of groundwater derived from episodic recharge on the hillslopes and in situ within valleys. However, as a result of significant increases in recharge following clearing, these palaeodrainages are now becoming saturated, and small natural discharge areas such as playas, which previously balanced recharge, are now too small to cope with increased surface and groundwater flows. Discharge areas are expanding and saline land is encroaching on farmland, threatening other assets such as towns, roads and remnant vegetation. Today between three and 15% of the wheatbelt shires, and a higher percentage of valley floor farmland is saline. A larger area of between 22 and 34% is likely to have shallow watertables and much of it be saline, if current trends in groundwater levels are maintained. In addition, few management options are available to reduce recharge, the area required for effective management is large (> 50%) and there remains considerable uncertainty as to the effectiveness and economics of discharge based options. Despite this uncertainty, farmers threatened by salinity have recognised that engineering options represent the most likely means of unilaterally managing salinity. Many also realise that discharge areas, saline or with a shallow watertable, are a complex mosaic of land with differing salinity levels and capabilities. Given current levels of effectiveness of management options, added economic incentives for the use of wheatbelt valleys is required. These may be needed to both partially refund recovery of land where engineering options have been used or as a means to develop a new resource and associated industry. We believe that this incentive, should it exist, may potentially come from the longer-term development of the large (1000 GL/yr) and saline (> 30,000 mg/L) groundwater resources which lie beneath wheatbelt valleys. While aquaculture, salt harvesting, desalinisation and the production of solar energy are all possible, there remains a considerable economic gap to be filled before many of these new industries become reality and wheatbelt valleys change their current landuse and emphasis on reclamation for agriculture.
... This rainfall gradient generates variability in playa hydroperiod and filling frequency. The origin and geomorphology of the system has been discussed in detail elsewhere (Killigrew and Gilkes 1974; Beard 1999 Beard , 2000 Boggs et al. 2006). Six small playas (>3 km 2 ), comprising three pairs of adjacent lakes, were chosen for detailed investigation, and labelled Mongers A (MONA), Mongers B (MONB), Kadji A (KA), Kadji B (KB), Morawa A (MA) and Morawa B (MB). ...
Article
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Diatom diversity of six small playa lakes within the Yarra Yarra drainage system, Western Australia, and the environmental variables likely to influence their distribution was investigated. Thirty-one pennate diatom taxa were identified. Taxa consisted of facultative planktonic and periphytic, circumneutral to alkaliphilous or pH-indifferent forms with known adaptations to saline conditions and fluctuations in salinity in NaCl dominated waters. Data were analysed by ordination (MDS and PCA), hierarchical clustering (CLUSTER), permutation-based hypothesis testing (ANOSIM) and comparative tests on similarity matrices (RELATE). Water depth accounted for the majority of variation in the environmental data. REALTE comparisons of environmental and taxa data did not produce a significant correlation value. We propose that the poor concurrence of the datasets was influenced by the wide ecological tolerances of the taxa recorded, some crucial unmeasured environmental variable/s, possible geographical regionalisation and/or unsampled taxa variability owing to the stochastic nature of the wetlands. Broad patterns of distribution were related to hydroperiod and some taxa groups were loosely associated with environmental groups consistent with established ecological tolerances for the taxa.
Chapter
Critical Zone Observatories (CZOs) are a global attempt to understand the function of the vertical ‘geo-bio-atmosphere boundary down to the bedrock’ critical zone (CZ) profile by characterising its physical, chemical and biological structure, learning how matter and energy are stored, transported and transformed within the CZ, and elucidating how this storage, movement and transformation contribute to the evolution of CZ structure.
Article
The Eocene was a critical period of global plate reorganization and it also saw the Earth's climate transition from the warmhouse state to the coolhouse state. Reconstructing the Eocene sedimentary history in the climate-sensitive Southern Ocean is important for understanding paleoenvironmental changes in response to the accelerated Australia/Antarctica separation and global cooling throughout the middle and late Eocene. Here, we present the first detailed multiproxy record of a continuous sequence from International Ocean Discovery Program (IODP) Site U1514 in the Mentelle Basin off southwestern Australia. Our aim is to reconstruct the sediment provenances and paleoenvironmental evolution in response to the abovementioned climatic and tectonic changes in the mid-high southern latitudes during the Eocene. Provenance analyses based on Sr-Nd isotopes, trace elements, and clay mineral assemblages suggest that Eocene sediments at Site U1514 predominantly originated from the southwestern Australian continent and the Naturaliste Plateau. Sediment provenance variations during the middle Eocene indicate that the onset of fast separation between Australia and Antarctica at 43 Ma caused an increased supply of volcanic materials from the Naturaliste Plateau between 43 and 38 Ma. Terrigenous inputs to the Mentelle Basin during the middle Eocene were primarily controlled by paleoclimate changes rather than tectonic processes because coeval clay mineralogical changes (higher kaolinite/smectite ratio and MARkaolinite) indicate a period of stronger physical erosion and chemical weathering on the western Australian continent that resulted in increased terrigenous materials delivered to the Mentelle Basin. Our results reveal a 5 Myr-long (43–38 Ma) warming reversal in the southern mid-high latitudes, providing an exception to the generally short-lived (10–100 kyr-long) hyperthermals that interrupted the long-term global cooling throughout the middle to late Eocene. As for the late Eocene (38–37 Ma), tectonic processes related to the sudden acceleration in seafloor spreading in the Tasman Sea led to the exposure of shallower areas, resulting in rapid detritus accumulation at the study site. During the late Eocene (37–34 Ma), major sediment provenance shifted from distal source areas (e.g., the Yilgarn Craton) to relatively proximal sources (e.g., the Leeuwin Block and Perth Basin). We interpret that the regional uplift in southwestern Australia and coeval climate cooling resulted in the diversion and inactivation of large drainage systems, thus blocking the transportation of sediment from distant regions.
Article
The flora of the Southwest Australian Floristic Region (SWAFR) is characterized by remarkable richness, endemism, spatial turnover and numbers of threatened taxa. Increasingly, evolutionary history is recognized as contributing to SWAFR biogeographical patterns, culminating in the theory of old, climatically buffered, infertile landscapes (OCBILs) [and their counterpoint: young, often disturbed, fertile landscapes (YODFELs)]. For the SWAFR, we: (1) developed a spatially explicit distribution of OCBILs and YODFELs; (2) analysed the spatial distribution of Threatened and Priority (Data Deficient) flora; and (3) tested the hypotheses that Threatened and Priority flora will be most strongly represented in OCBILs and will have small geographical ranges. We found that OCBILs and YODFELs dominated spatially distinct portions of the SWAFR. Threatened and Priority flora were not uniformly or randomly distributed and were more strongly characterized by narrow-range endemics than the non-Threatened flora. The occurrence of Threatened and Priority flora was positively correlated with the age of surface exposure of landscape features and unique geological features of limited extent (if not YODFELs). The concentration of Threatened flora in OCBILs provides the opportunity to improve conservation management through investigations of how plant traits favoured by evolution in OCBILs might increase or decrease the susceptibility of the flora to anthropogenic threats.
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This three-part paper reports the results of prospectivity modeling and quantitative resources assessments of the calcrete-hosted surficial uranium deposits in Western Australia. The study area boundary conforms to the Western Australian part of the Deserts and Xeric Shrublands biome, which is geologically, physiographically and climatologically permissive for calcrete-hosted surficial uranium deposits. In this Part 2, we apply three independent prospectivity models, which include two data-driven models (the weights of evidence and the neural network models) and a knowledge-driven model (fuzzy inference system), to assess the potential of calcrete-hosted surficial uranium deposits within the palaeochannels of the study area. The model inputs are derived based on the conceptual model of calcrete-hosted surficial uranium systems described in Part 1. A preservation potential filter is applied to account for post-formation preservation of deposits. The performance of the models is statistically assessed using capture efficiencies and receiver operating characteristic curve. Several sections of palaeodrainage systems in the Yilgarn craton, Gascoyne province, Musgraves block and Paterson orogeny are delineated as highly prospective for calcrete-hosted surficial uranium deposits. The Yilgarn and Gascoyne are established provinces for calcrete-hosted style of uranium mineralization; however, this study indicates that the preservation potential in the Gascoyne province is reduced, and hence this province may not contain large deposits comparable in size to the Yilgarn craton. A major outcome of modeling is the identification of new greenfields exploration targets for calcrete-hosted surficial uranium deposits in the underexplored Paterson orogen and Musgraves block.
Chapter
The term “playa” or “pan” applies to individual arid zone basins of varying size and origin that are subject to ephemeral surface water flows (Shaw and Thomas, 1989) such that lakes may occur within playas as permanent or ephemeral features. Playas in Australia are often geologically young (Quaternary) features developed in arid environments and are often dry due to evaporation (Boggs et al., 2006). Although playas are a response to tectonics, climate change, and eolian and fluvial processes, the majority of the scientific literature considers either their origin within a regional context, or the development dynamics of individual playas (e.g., Bettenay, 1962). However, where playas are developed within paleodrainage channels, they may exist as isolated features, but more often they exhibit a degree of hydrological interconnectivity with other playas to form "playa chains” such that the development history of an individual playa cannot be addressedwithout consideration of its neighbors.
Chapter
The geomorphology of Gondwana was different from that of the fragments created when it broke up. These fragments, now continents and large islands, inherited some features from the original Gondwana landscape, including major drainage patterns and planation surfaces. Other features including Great Escarpments could only form after the break-up, and some erosion surfaces are also formed after break-up and graded to new base levels. The continents of Gondwana derivation have geomorphic histories that have many features in common but also some distinct features peculiar to individual fragments. In this chapter I describe the geomorphology of the Gondwana fragments and give an outline of the various ways the evidence has been interpreted, including the major controversies. All the fragments have a succession of planation surfaces but seldom the neat step-like succession of simplistic descriptions. Their age and correlation is difficult to determine, as is their relationship to tectonics and changes of climate. Lester King was perhaps premature in his attempts to correlate planation surfaces all over the world, but his aim is still a valuable lead. Since his day there has been a profusion of more detailed local studies, and the next task is to integrate them into a new Gondwana-wide synthesis.
Article
The Kent River flows from semi-arid headwaters in the agricultural (wheatbelt) region of Western Australia to a wetter and forested lower-catchment. It is set in an atypical fluvial environment, with rainfall decreasing inland towards a low-relief upper catchment. Replacement of native deep-rooted perennial vegetation with shallow-rooted seasonal crops has altered the hydrology of the upper catchment. Clearing for agriculture has also increased recharge of regional groundwater systems causing groundwater to rise and mobilise salt stores. This has increased stream salinity which has degradation riparian vegetation and decreased flow resistance. Elevated groundwater has also affected streamflow, increasing flow duration and annual discharge. The altered hydrological regime has affected geomorphic stability, resulting in channel responses that include incision and removal of uncohesive material. Channel response is variable, showing a high dependence on channel morphotype, channel boundary material and severity of salinity (degree of vegetation degradation). Response in confined reaches bounded by sandy material has been characterised by minor lateral bank erosion. In the fine-grained, wider, low-gradient reaches, mid-channel islands have been stripped of sandy sediment where vegetation has degraded. Following an initial period of high erosion rates in these reaches, the channel is now slowly adjusting to a new set of boundary conditions. The variable response has significant implications for management of salt affected rivers in southwestern Australia.
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In arid Western Australia external paleodrainge systems are marked by playas. These systems have been reconstructed using contour maps of the present land surface, combined with geological and other maps. The paleodrainages are well preserved in an extensive, relict duricrusted landscape, and most patterns formed during the Late Cretaceous to Early Tertiary. Significant flow in the central-desert paleodrainages stopped before the mid-Miocene. The paleodrainage patterns are preserved because of the tectonic stability of the area, and because a change from a humid to an arid climate during the Tertiary, which slowed down erosion and sedimentation
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The Middle Eocene — Oligocene macroflora from West Dale in southwestern Australia is described. The majority of fossils are leaves, and 35 taxa are described and illustrated, including 12 new fossil species and three previously described species (two fossil, one extant). There are clear floristic similarities with Eocene — Oligocene macrofloras in eastern Australia (e.g. Agathis, Dacrycarpus, Gymnostoma, Cunoniaceae, Nothofagus, Lauraceae, Banksieaephyllum), but the West Dale flora is unique in the predominance of Myrtaceae and, to a lesser extent, Proteaceae. The West Dale macroflora offers support for the hypothesis that the Australian sclerophyll flora evolved primarily in response to low nutrient levels (especially phosphorus) and was pre-adapted to developing xeric climates. However, alternative hypotheses cannot be ruled out.
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Landforms and soils of part of the Darling Range, Western Australia, are described. A controlling factor is rejuvenation of drainage following Tertiary (?) uplift of the Western Australian Shield, and the extent and effects of this are assessed. Broad divides carry remnants of old landscapes extensively preserved further inland, while sequential changes in valley forms and soils suggest stages in uplift. Upstream, valleys are broad and shallow, with low gradients, and deep weathering and old soils are widespread. Downstream, stages of progressively increasing sharpness and depth of incision of valleys are observable, and while deep weathering and old soils are preserved on the uplands, the steeper valley sides carry younger and fresher soil materials. Consideration of long and cross sections and soil patterns permit some separation of the effects of structure, uplift, and climate in landscape development.
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Completion of the latest series of topographic maps at scales of 1:100 000 and 1:250 000 by the Commonwealth agency AUSLIG and of the 1:250 000 geological maps by the Geological Survey of WA has provided much new valuable data on the topography and surface features of the Western Shield in Western Australia. It has long been known that the Shield has a longitudinal central watershed or so-called continental divide separating drainages to east and west, and it is now possible to plot this precisely following contours on the new maps. The lateral watersheds bounding the catchments of rivers, still mainly active, which drain to the west coast have also been mapped. The central watershed rises steadily from 400 m asl at its southern end to a maximum of 750 m near its northern end, in conformity with a general tilt of the Shield. The lateral watersheds slope down gradually from the central watershed to ± 250-300 m at the western edge of the Shield, a height corresponding, it is suggested, to Cretaceous sea level. Metamorphic belts incorporated in the general granite-gneiss ground mass of the Yilgarn Craton have only very local effects on drainage patterns. On the Yilgarn Craton the mapped watersheds tend to be covered by sandplains, varying from complete cover in the south to partial in the north. Whereas the superficial deposits on these sandplains may be of different ages, i e subsequently disturbed, reworked or replaced, the saprolite beneath is suggested to conform to a palaeosurface resulting from planation during the Mesozoic era, when the drainage systems of today also originated.
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This paper revises the stratigraphy of the Lefroy and Cowan palaeodrainages, and compares it with that of the Eucla and Bremer Basins. The definition of the Eundynie Group is modified, and the terms Redmine Group, Revenge Formation, Gamma Island Formation, Polar Bear Formation, Roysalt Formation, and Beta Island Member are proposed. The Eocene palaeodrainage succession is placed in the Eundynie Group, and the post-Eocene succession in the Redmine Group. -from Author
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The Yilgarn River, predecessor of the Swan River, was a major river during the Tertiary before uplift of the Yilgarn Craton and the Darling Range. Tectonic activity and climatic change associated with movement of the Australian Plate caused this river system to dry up, with the formation of riverine playa lakes in its abandoned channel. During Pliocene time, siliciclastic sediments and peat were deposited in the paleochannel system in the central part of the catchment. Other sediments vary in age from Pliocene to Miocene. The oldest sediments (Eocene) are preserved in crevices in uplifted areas of the Darling Range and at the base of paleochannels. In Lake Deborah, prolonged arid periods occurred when no salt was added to the lake. For most of its history, the lake has remained a NaCl repository. -from Author
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A study of available echo sounding data, coupled with a recent Precision Depth Recorder section along the continental slope, has enabled detailed plotting of submarine canyon axes along the continental margin of southern Australia. Groups of large submarine canyons are confined to the continental slope in areas of shallow basement rock, opposite on-shore areas of Cambrian to Precambrian rocks. Areas of Tertiary basin development, both on-shore and on the continental shelf, lack a development of major submarine canyons on adjacent continental slopes. Relics of Early Tertiary or pre-Tertiary large-scale drainage systems on the ancient land surface of the Great Plateau, of southwestern Australia, may be related to the large submarine canyons.Results of the study indicate at least an Early Tertiary age for initial sub-aereal cutting of heads of the large canyons. Smaller canyons, occurring on slope areas in the vicinity of Tertiary basins, may be related to Pleistocene low sea level stands.
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New earthquake risk maps, based on the Cornell-McGuire methodology, have been prepared for the Australian continent and continental margins. The risk is depicted as contours of peak ground velocity, acceleration and ground intensity with a 10% probability of being exceeded in 50 years. The earthquake process was assumed to be Poissonian and consequently foreshocks and aftershocks were eliminated. The estimated maximum earthquake magnitude likely to be expected in each zone was assumed to be half a magnitude unit greater than the largest recorded Richter magnitude for that zone. For areas outside the defined source zones, normalized background seismicity levels were used in the risk estimates. Separate relationships for the attenuation of ground intensity with hypocentral distance using a scaling law of the Kanai form were obtained for western, southeastern and northeastern Australia and for Indonesian earthquakes felt in northern Australia. These were based on the determination of mean isoseismal radii from isoseismal maps of Australian earthquakes and hence reflect average site conditions. Conversions of ground intensity (I, on the Modified Mercalli scale) to peak ground acceleration (A, in m/s2) and velocity (v, in mm/s) were carried out using the empirical relations log A=I/3.1 — 2.3 and 21= 7v/5. Recordings of peak ground acceleration were used where available to check the resultant acceleration and velocity attenuation functions. This re-evaluation of seismic risk in Australia may be used as the basis for a revision of the seismic zone map in the current Australian Building Code.
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The Salt River System forms the connection between the saline lakes of the Yilgarn River catchment in the east and the rejuvenated Avon River System in the west. Judging from the age of the deposits in the palaeochannels of the Salt River after the Darling uplift and from the deltaic deposits of the river before the uplift, it appears that the river has been occupying this same course since the Early Tertiary. The uplift dammed the course of the river and caused the formation of large inland lakes. The inland lake at Yenyening persisted for a long time until the opening of the northern outlet of the Avon. This explains the absence of sedimentary deposits from the Avon in the Perth Basin during the closure time. The relatively thick sediments that fill up the palaeochannels comprise three formations of the Salt River Group: South Caroline Clay, Yenyening Formation and Quairading Sandstone. The reconstruction of the palaeoriver showed that the river was occupying a steep gorge about 70 m deep with a slope of about 0.35 m km.
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The main features of climate and geology relevant to a discussion of the soils and landscapes of Western Australia are briefly reviewed. The pattern of drainage is described in terms of six drainage divisions, each with characteristic physiography and soils. In the interior, this involves a reconstruction of an ancient drainage system, based on the maps of the Atlas of Australian Soils. It is shown, on a continental scale, that the major divides are characterised not only by deep, chemically weathered, often lateritic profiles, but also by extensive sandy deposits derived from these preweathered materials.
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Pollen assemblages indicate an Early Pliocene age for sediments in the Lake Tay area, south-west of Norseman, W.A. They also show unexpected similarities to assemblages of the same age from south-eastern Australia and suggest that regional phytogeographic differentiation of the flora of southern Australia was less pronounced in the Early Pliocene than usually supposed. This implies that considerable regional differentiation of southern Australian floras has taken place in a relatively short period, principally during the past 4 or 5 million years. Although the dominant elements in the pollen spectrum indicate a warm temperate open-forest with a lake edge or marsh component, small numbers of the pollen of Nothofagus (brassii-type) and some podocarpaceous conifers are also present. These suggest a wetter climate and may have derived from small stands surviving in refugia on high country to the east or south of Lake Tay.
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Biotite from granite and gneiss in the southwestern part of the Yilgarn Craton near Perth has been dated by the Rb‐Sr technique at about 430–500 Ma in a belt at the western edge of the craton. The belt widens southward from 30 km near Perth to 55 km east of Harvey. The eastern boundary of the belt passes along the east margin of the Saddleback greenstone belt. A transition zone 15–40 km wide separates the belt of young dates from an eastern chronological plateau where biotite dates, mainly 2300–2600 Ma, are marginally younger than regional Rb‐Sr whole rock dates which average about 2550 Ma. In contrast to biotite dates, whole rock dates greater than 2500 Ma persist to the western edge of the craton. The 430–500 Ma dates probably represent resetting during uplift in the Early Palaeozoic.
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Several 50–100 mile long canyons traverse a 100 mile by 100 mile amphitheatre-like depression that occurs from the shelf break to depths of over 2,000 fathoms on the continental slope of Australia east of Bass Strait. Bass Canyon heads in at least three major tributaries at depths of 60–90 fathoms, is about 100 miles long and has a 40 mile long and 2–5 mile wide flat floor flanked by 700 fathom high walls and occupies the central depths of the continental slope depression directly offshore from the main shelf graben. Flinders Canyon, lying south of Bass Canyon, is generally narrow and gorge-like, has two major tributaries, and extends to depths of 2,100 fathoms over a distance of 60 miles.Following deposition of about 5,000–10,000 ft. of mostly deltaic and terrestial sediments in the Late Jurassic to Late Eocene in the Gippsland Basin there have been three main periods of canyon erosion and sedimentation. The first period occurred in the Late Eocene to Early Oligocene, the second in the Miocene and the third was the formation of the contempory canyon system which was initiated in the Pliocene.Marine processes associated with these canyon systems have been responsible for prograding the continental slope 50–70 miles and removing about 20,000 cubic miles of sediment from the Australian mainland since the Late Eocene.
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Submarine canyons have generally been lumped together and a common explanation of their origin has been sought. The author suggests that some, named submarine ravines, are drowned river valleys (Corsica). The other extreme, the New England type, is the result of glacial turbidity currents. Daly's explanation of the California type as drowned subaerial valleys, smothered by sediment, and excavated by glacial and recent turbidity currents is accepted with some change of emphasis. This type is thus tentatively ascribed to the same turbidity-current mechanism, but erosion has exhumed some buried valleys, cleaned out parts of others, laid bare parts of old mountain slopes, and has even developed new channels. Shepard's new hypothesis of drowned river valleys kept permanently open by submarine processes, comes near to this picture and is accepted for the submarine ravines, but it cannot account for the features that indicate submarine erosion in the recent past off New England and California. His main argument against erosion by turbidity currents is the absence of scour on lake-delta fronts, but conditions in lakes must be highly adverse to erosion and hence this objection is eliminated. On the other hand Ewing and his associates give convincing evidence for the great importance of turbidity flow in the oceans.
Article
Incision of the palaeodrainage system occurred during Jurassic times. Reversal of the Cowan palaeodrainage channel occurred prior to Jurassic deposition in the Bremer Basin, resulting in the Cowan palaeodrainage channel flowing south to the Bremer Basin and the Lefroy palaeodrainage channel flowing east to the Eucla Basin. In post-Eocene times, the palaeodrainage channels were fragmented into a chain of lakes, accompanied by deposition of the fluvio-lacustrine Redmine Group. Deposition of the clastic-dominated Revenge Formation took place during the Miocene. Limited carbonate deposition also occurred in both lakes. From the Pliocene onwards, increasing aridity led to deposition of the evaporitic Roysalt Formation in Lake Lefroy and Polar Bear Formation in Lake Cowan. -from Author
Article
The continental margin of southern Australia is divisible into four contrasting physiographic provinces on the basis of shelf-break depth and continental slope gradient. These provinces correspond with four structural provinces, which in turn are intimately related to the geology. Zones of relatively stable pre-Mesozoic shallow basement extending out to the shelf edge characterize two of the above provinces, one of which occurs south of Kangaroo Island and the other off Tasmania's northwest coast. In contrast, zones of Mesozoic to Tertiary deep offshore basin formation typify the remaining two provinces, one being situated at the eastern end of the Great Australian Bight and the other along the seaward portion of the Otway Basin. A possible model is presented, based on an assumption of continental rifting and drifting, which explains the structural peculiarities of that portion of the Otway Basin which occurs beneath the present continental shelf and upper slope.
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