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Research about South Australia

Source-linked reports with geographic coverage including South Australia.

7 recordsLinked to original sources
USGS2016

Conductivity response to intraplate deformation: Evidence for metamorphic devolatilization and crustal‐scale fluid focusing

We present two‐dimensional electrical resistivity models of two 40 km magnetotelluric (MT) profiles across the Frome Embayment to the east of the northern Flinders Ranges, South Australia. The lower crust shows low resistivity of 10 Ω m at around 30 km depth. The middle crust is dominated by resistive (>1000 Ω m) basement rocks underlying the Flinders Ranges. Adjacent to the ranges, conductive lower crust is connected to vertical zones of higher conductivity extending to just below the brittle‐ductile transition at ∼10 km depth. The conductive zones narrow in the brittle upper crust and dip at roughly 45° beneath the surface. Zones of enhanced conductivity coincide with higher strain due to topographic loading and sparse seismicity. We propose that fluids are generated through neotectonic metamorphic devolatilization. Low‐resistivity zones display areas of fluid pathways along either preexisting faults or an effect of crustal compression leading to metamorphic fluid generation. The lower crustal conductors are responding to long‐wavelength flexure‐induced strain, while the upper crustal conductors are responding to short wavelength faulting in the brittle regime. MT is a useful tool for imaging crustal strain in response to far‐field stresses in an intraplate setting and provides important constraints for geodynamic modeling and crustal rheology.

South Australia↗
USGS2012

Gravity survey of the Mount Toondina impact structure, South Australia

Gravity and seismic reflection data, together with geologic mapping, indicate that the Mount Toondina feature in South Australia is best interpreted as an eroded 4-km-diameter impact structure consisting of a ring structural depression surrounding a pronounced central uplift. Beds at the center of the structure within the central uplift have been raised as much as 200 m from depth and deformed by convergent flow. Seismic reflection data indicate that deformation extends to depths of only ≈800 m; at greater depths the reflectors are nearly flat lying, indicating little or no deformation. Gravity data show residual anomalies of +1.0 mGal coincident with the central uplift and a −0.5 Mgal low associated with the ring structural depression. Modeling of the gravity data indicates that relatively high-density material occurs within the central uplift, whereas the ring depression is filled with low-density material. The deformation at Mount Toondina is typical of a complex impact crater; the 4-km diameter is consistent with the expected threshold size for complex craters formed in weak to moderate strength sedimentary rocks.

South Australia↗
USGS2011

Dust: Small-scale processes with global consequences

Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored.

Eos, Transactions, American Geophysical Union↗
USGS2011

Fire in southern Australia

The mediterranean-type climate (MTC) in Australia spans from the southwestern part of Western Australia to include much of South Australia and western Victoria (Fig. 8.1), which covers a longitudinal distance second only to the Mediterranean Basin MTC region. As in other MTC regions, the highly fire-prone evergreen sclerophyllous shrub and tree mediterranean-type vegetation (MTV) extends much further east and north into climatic zones that are not MTC. Australia, however, is distinctly unlike other MTC regions in that fire-prone MTV is extensive across the southern part of the continent and transcends climatic boundaries with relatively subtle changes in community structure and composition. Sclerophyllous MTV dominates both the MTC region of the southwestern corner of the continent as well as the southeastern corner under an aseasonal climate. Both regions share a common fire season of summer to early autumn (McArthur 1972); however, the MTC southwest has a potential fire season every summer whereas in the southeast it is tied to weather anomalies that occur once to several times a decade. Mediterranean-type Vegetation Within the southern Australian MTC zone (Fig. 8.1) evergreen sclerophyllous vegetation dominates. Such MTV is sometimes defined as shrub dominated (Specht 1979), and indeed large areas of sclerophyllous heaths (see Fig. 1.6f), shrublands (Fig. 8.2a) and mallee (Fig. 8.3) occur. However, woodlands and forests form integral parts of the MTC biome (Dell et al . 1989; Gill 1994), and thus MTV includes shrublands, woodlands and forests, and in southern Australia they dominate both in the MTC region and outside that climatic zone (Fig. 8.1). MTV is found across the southern temperate latitudes of Australia (Table 8.1) in an arc below about 30° latitude, accounting for dominant vegetation types in infertile habitats throughout temperate Australia. We specifically focus on the various heaths, shrublands and dry sclerophyll forests that constitute the most fire prone communities in these temperate landscapes. Although similar fire-prone MTV heathlands occur extensively within the tropics on the northern end of the continent (Keith et al . 2002; Russell-Smith & Stanton 2002), here we focus on the temperate MTV, but do consider broader relationships with other adjoining vegetation types (e.g. wet sclerophyll forests, rainforests, and various arid and semi-arid woodlands and shrublands).

South Australia↗
USGS2003

Paleoseismicity of two historically quiescent faults in Australia: Implications for fault behavior in stable continental regions

Paleoseismic studies of two historically aseismic Quaternary faults in Australia confirm that cratonic faults in stable continental regions (SCR) typically have a long-term behavior characterized by episodes of activity separated by quiescent intervals of at least 10,000 and commonly 100,000 years or more. Studies of the approximately 30-km-long Roopena fault in South Australia and the approximately 30-km-long Hyden fault in Western Australia document multiple Quaternary surface-faulting events that are unevenly spaced in time. The episodic clustering of events on cratonic SCR faults may be related to temporal fluctuations of fault-zone fluid pore pressures in a volume of strained crust. The long-term slip rate on cratonic SCR faults is extremely low, so the geomorphic expression of many cratonic SCR faults is subtle, and scarps may be difficult to detect because they are poorly preserved. Both the Roopena and Hyden faults are in areas of limited or no significant seismicity; these and other faults that we have studied indicate that many potentially hazardous SCR faults cannot be recognized solely on the basis of instrumental data or historical earthquakes. Although cratonic SCR faults may appear to be nonhazardous because they have been historically aseismic, those that are favorably oriented for movement in the current stress field can and have produced unexpected damaging earthquakes. Paleoseismic studies of modern and prehistoric SCR faulting events provide the basis for understanding of the long-term behavior of these faults and ultimately contribute to better seismic-hazard assessments.

South Australia↗
USGS1988

Refined Proterozoic evolution of the Gawler Craton, South Australia, through U-Pb zircon geochronology

Through the application of both conventional U-Pb zircon analyses and small-sample U-Pb isotopic analyses, the nature and timing of tectonic events leading to the formation of the Gawler Craton have been defined more precisely. Constraints on deposition of Early Proterozoic iron formation-bearing sediments have been narrowed down to the period 1960-1847 Ma. Deformed acid volcanics, including the economically important Moonta Porphyry, have zircon ages of ∼ 1790 and 1740 Ma. The voluminous acid Gawler Range Volcanics and correlatives to the east were erupted over a short interval at 1592 ± 2 Ma, and were intruded by anorogenic granites at ∼ 1575 Ma. Small-sample zircon analyses proved to be an extremely valuable adjunct to conventional analyses, generally yielding more-concordant data which forced a curved discordia through an upper intercept slightly younger than from a conventional straight-line discordia.

South Australia↗