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Research about Australia

Source-linked reports with geographic coverage including Australia.

At least 109 records · Page 6Linked to original sources
USGS1999

Total petroleum systems of the Bonaparte Gulf Basin area, Australia; Jurassic, Early Cretaceous-Mesozoic; Keyling, Hyland Bay-Permian; Milligans-Carboniferous, Permian

The Bonaparte Gulf Basin Province (USGS #3910) of northern Australia contains three important hydrocarbon source-rock intervals. The oldest source-rock interval and associated reservoir rocks is the Milligans-Carboniferous, Permian petroleum system. This petroleum system is located at the southern end of Joseph Bonaparte Gulf and includes both onshore and offshore areas within a northwest to southeast trending Paleozoic rift that was initiated in the Devonian. The Milligans Formation is a Carboniferous marine shale that sources accumulations of both oil and gas in Carboniferous and Permian deltaic, marine shelf carbonate, and shallow to deep marine sandstones. The second petroleum system in the Paleozoic rift is the Keyling, Hyland Bay-Permian. Source rocks include Lower Permian Keyling Formation delta-plain coals and marginal marine shales combined with Upper Permian Hyland Bay Formation prodelta shales. These source-rock intervals provide gas and condensate for fluvial, deltaic, and shallow marine sandstone reservoirs primarily within several members of the Hyland Bay Formation. The Keyling, Hyland Bay-Permian petroleum system is located in the Joseph Bonaparte Gulf, north of the Milligans-Carboniferous, Permian petroleum system, and may extend northwest under the Vulcan graben sub-basin. The third and youngest petroleum system is the Jurassic, Early Cretaceous-Mesozoic system that is located seaward of Joseph Bonaparte Gulf on the Australian continental shelf, and trends southwest-northeast. Source-rock intervals in the Vulcan graben sub-basin include deltaic mudstones of the Middle Jurassic Plover Formation and organic-rich marine shales of the Upper Jurassic Vulcan Formation and Lower Cretaceous Echuca Shoals Formation. These intervals produce gas, oil, and condensate that accumulates in, shallow- to deep-marine sandstone reservoirs of the Challis and Vulcan Formations of Jurassic to Cretaceous age. Organic-rich, marginal marine claystones and coals of the Plover Formation (Lower to Upper Jurassic), combined with marine claystones of the Flamingo Group and Darwin Formation (Upper Jurassic to Lower Cretaceous) comprise the source rocks for the remaining area of the system. These claystones and coals source oil, gas, and condensate accumulations in reservoirs of continental to marine sandstones of the Plover Formation and Flamingo Group. Shales of the regionally distributed Lower Cretaceous Bathurst Island Group and intraformational shales act as seals for hydrocarbons trapped in anticlines and fault blocks, which are the major traps of the province. Production in the Bonaparte Gulf Basin Province began in 1986 using floating production facilities, and had been limited to three offshore fields located in the Vulcan graben sub-basin. Cumulative production from these fields totaled more than 124 million barrels of oil before the facilities were removed after production fell substantially in 1995. Production began in 1998 from three offshore wells in the Zone of Cooperation through floating production facilities. After forty years of exploration, a new infrastructure of pipelines and facilities are planned to tap already discovered offshore reserves and to support additional development.

Open-File Report↗
USGS1995

The minimal response to contact metamorphism by the Devonian Buchan Caves Limestone, Buchan Rift, Victoria, Australia

A 2.2 m thick, Late Eocene (?) dike that intruded the Devonian Buchan Caves Limestone, near Murrindal, Victoria, has produced a narrow contact aureole only centimeters wide in the adjacent host rock. Mean solid bitumen reflectance ranges from about 2.4 to 2.7% and shows little change up to 6 m away from the dike contact. Carbon and oxygen isotope values also show little change except at the dike contact. The most detectable response of the rock to contact metamorphism is the proportion of solid bitumen grains with finely granular mosaic structure increase towards the dike. Also under cathodoluminescence (CL) excitation, the host rock is initially observed to be recrystallized to a uniform bright orange color. By 1 cm away from the contact, however, CL shows preservation of sharp boundaries in finely zoned burial cements. A regional study of thermal maturation and a geothermometer based on solid bitumen reflectance indicate paleotemperatures near 200°C were widespread in the Buchan Rift during peak burial near the time of the Devonian Tabberabberan Deformation. The lack of response of the Buchan Caves Limestone to contact metamorphism is attributed to: (1) prior heating to near 200°C; and (2) the fact that the dike intruded into cool, near surface, low-porosity rocks which may have been in the vadose zone.

eastern Victoria↗
USGS1995

Volcanic investigations in the Commonwealth of the Northern Mariana Islands, April to May 1994

A team of U.S. Geological Survey geologists, a seismologist, and technicians gathered new geologic, seismic, and deformation data in the Commonwealth of the Northern Mariana Islands (CNMI). Nine volcanic islands on the active East Mariana Ridge north of Saipan were examined between April 20 and May 3, 1994. In addition, a new radio-telemetry seismic station was installed on the island of Agrihan (also spelled Agrigan). This report describes our continuing efforts, that began in May 1981, to establish volcano monitors and to assess hazards in the CNMI. Our previous visits, from September 1990 to May 1992, are documented in Moore and others (1991, 1993). Regional seismicity of the Mariana Island region, as recorded by the USGS National Earthquake Information Center (NEIC), included at least 324 events between January 1, 1991, and February 4, 1994. The largest event was a M 8.1 Guam earthquake on August 8, 1993, which caused extensive damage to that island and was felt on Saipan. Intermittent seismic activity continues to occur in the Anatahan-Sarigan, Guguan-Alamagan-Pagan, and PaganAgrihan-Asuncion areas. Mount Pagan volcano was actively erupting ash during our 11 days on the island of Pagan. We were able to document seismicity and ground deformation associated with this volcanic activity. None of the other subaerial volcanoes in the chain showed signs of eruptive activity during our visit, but an overflight in a fixed-wing aircraft by geologist Richard Moore and CNMI Lieutenant Governor Jesus Borja detected an apparent submarine eruption between Farallon de Pajaros (also known as Uracas or Uracus) and Maug. The only surveillance of the three uninhabited islands of Farallon de Pajaros, Maug, and Sarigan was by aerial reconnaissance. Geologists studied the other six islands in greater detail by field mapping and aerial surveillance. Electronic distance measurement (EDM) permanent-glass monitor lines were measured on Agrihan, Pagan, and Anatahan. The majority of line-length changes on Agrihan were insignificant (<16 mm). Mount Pagan's south EDM monitor was reestablished, and 1994 results, compared with 1983 measurements, show large changes associated with renewed volcanic activity. Contractions of 59 mm (stations INS to REF) and 157 mm (stations INS to MID) were measured on the south monitor. The southwest Pagan EDM monitor showed a 56 mm contraction for the same period (stations PAGAN 1 to RIDGE 2). Line-length change of this sense and magnitude usually indicates that inflation has occurred in the volcano. Measurements during the 1994 visit to Pagan Island showed no significant changes (for all measurements made during April-May 1994). Anatahan also showed changes as large as -50 mm, accumulated over a time span of approximately two years. Temperatures and pH values of hot spring waters on Agrihan, Pagan, and Anatahan and fumaroles on Agrihan and Anatahan were measured. The temperature data indicated no significant change in the state of these volcanoes since 1992. We collected warm spring water from Lagoonam Sanhalom (Inland Lake) near Mount Pagan. In addition, we started geologic mapping on Asuncion and Guguan, collected charcoal to date three eruptions of Mount Pagan, and collected rocks on Asuncion, Guguan, Pagan, and Alamagan for petrographic and chemical studies. We conclude that the low and infrequent shallow seismicity, lack of significant deformation, and low fumarole temperatures suggest that no eruption is likely soon on Agrihan and Alamagan. Anatahan's deformation pattern continues to behave in an erratic manner. Because f the lack of seismicity, it seems unlikely that an eruption of Anatahan will occur soon. The persistent volcanic tremor and significant EDM changes on Mount Pagan mean that small explosive eruptions will continue to occur.

Mariana Islands↗
USGS1994

Clastic metasediments of the Early Proterozoic Broken Hill Group, New South Wales, Australia: Geochemistry, provenance, and metallogenic significance

Whole-rock analyses of samples of pelite, psammite, and psammopelite from the Early Proterozoic Broken Hill Group (Willyama Supergroup) in the Broken Hill Block, New South Wales, Australia, reveal distinctive geochemical signatures. Major-element data show high Al 2 O 3 and K 2 O, low MgO and Na 2 O, and relatively high Fe 2 O 3 T MgO "> Fe2O3TMgO ratios, compared to average Early Proterozoic clastic metasediments. High field strength elements (HFSE) are especially abundant, including Nb (most 15–27 ppm), Ta (most 1.0–2.2 ppm), Th (17–36 ppm), Hf (4–15 ppm), and Zr (most 170–400 ppm); Y (33–74 ppm) is also high. Concentrations of ferromagnesian elements are generally low ( Sc = < 20 ppm, Ni = ≤ 62 ppm, Co = <26 ppm; Cr = most < 100 ppm). Data for rare earth elements (REEs) show high abundances of light REEs ( La CN = 116–250 × chondrite; La CN = 437 in one sample), high La CN Yb CN "> LaCNYbCN ratios (5.6–13.9), and large negative Eu anomalies ( Eu Eu &#x2217; = 0.32&#x2013;0.57 "> EuEu∗= 0.32–0.57 ). The geochemical data indicate derivation of the metasedimentary rocks of the Broken Hill Group by the erosion mainly of felsic igneous (or meta-igneous) rocks. High concentrations of HFSE, Y, and REEs in the metasediments suggest a provenance dominanted by anorogenic granites and(or) rhyolites, including those with A-type chemistry. Likely sources of the metasediments were the rhyolitic to rhyodacitic protoliths of local quartz + feldspar ± biotite ± garnet gneisses (e.g., Potosi-type gneiss) that occur within the lower part of the Willyama Supergroup, or chemically similar basement rocks in the region; alternative sources may have included Early Proterozoic anorogenic granites and(or) rhyolites in the Mount Isa and(or) Pine Creek Blocks of northern Australia, or in the Gawler craton of South Australia. Metallogenic considerations suggest that the metasediments of the Broken Hill Block formed enriched source rocks during the generation of pegmatite-hosted deposits and concentrations of La, Ce, Nb, Ta, Th, and Sn in the region. Li, Be, B, W, and U in pegmatite minerals of the district may have been acquired during granulite-facies metamorphism of the local metasediments.

New South Wales↗
USGS1994

Thermoluminescence dating of Australian palaeo-earthquakes

Thermoluminescence (TL) dating is a useful tool for determining the age of prehistoric earthquakes by dating deposits that are stratigraphically related to fault scarps that formed during the earthquakes. TL dating of aeolian sand in the area of the 1988 Tennant Creek, Northern Territory, earthquakes provides evidence that similar earthquakes have not ruptured the causative faults for at least 50 ka. Pilot TL measurements of deposits associated with the Roopena and Ash Ridge fault scarps near Whyalla on Eyre Peninsula, South Australia, suggest an age of 140 ka for the Quaternary deposits associated with the formation of the scarps.

Eyre Peninsula↗
USGS1993

The common wolf snake, Lycodon aulicus capucinus, a recent colonist of Christmas Island in the Indian Ocean

The discovery of the common wolf snake, Lycodon aulicus capucinus , on Christmas I . in the Indian Ocean suggests that individuals of the species have colonised the island recently. On the basis of biological information for this widespread colubrid snake and for the brown tree snake, Boiga irregularis, a well-documented pest species on Guam, the establishment of the common wolf snake would pose a severe threat to the native fauna and ecology of Christmas I. Immediate research is needed to document the spread of the snake, to evaluate its effects on other fauna, and to control or eradicate the species before it becomes firmly established.

Christmas Island↗
USGS1993

Geologic investigations of Australian earthquakes: Paleoseismicity and the recurrence of surface faulting in the stable regions of continents

Earthquakes that occur in the stable regions of continents are very rare compared to those that occur along plate margins, such as the San Andreas fault system of western California. Worldwide, only 11 historic earthquakes in stable continental regions are known to have produced surface ruptures. Five of these have occurred in Australia since 1968 (see map, next page).

Earthquakes & Volcanoes (USGS)↗
USGS1991

Pliocene-Pleistocene coastal events and history along the western margin of Australia

Coastal deposits along the western coastal margin of Australia, a region of relative tectonic stability, record Plio-Pleistocene events and processes affecting the inner shelf and adjacent hinterland. Tectonic deformation of these deposits is more apparent in the Carnarvon Basin, and rather less so in the Perth Basin. The most complete record comes from the Perth Basin, where units of Pliocene and Pleistocene ages are well represented. In the Perth Basin, the predominantly siliciclastic Yoganup Formation, Ascot Formation and Bassendean Sand represent a complex of shoreline, inner shelf and regressive-dune facies equivalents, the deposition of which began at an undetermined stage of the Pliocene, through to the Early Pleistocene. The deposition of this sequence closed with a major regression and significant faunal extinction. Bioclastic carbonates characterize the Middle and Late Pleistocene of the Perth and Carnarvon basins. Fossil assemblages include a distinct subtropical element, unknown from the Ascot Formation and suggesting a strengthening of the Leeuwin Current. The estuarine arcoid bivalve Anadara trapezia characterizes assemblages of Oxygen Isotope Stages 5 and 7 in the Perth and Carnarvon basins, where it is now extinct. Deposits of Substage 5e (Perth Basin) also record a southerly expansion of warm-water corals and other fauna consistent with shelf temperatures warmer than present. New uranium-series ages on corals from marine sequences of the Tantabiddi Member, of the Bundera Calcarenite of the western Cape Range are consistent with the ‘double peak’ hypothesis for levels of Substage 5e but the evidence remains less than conclusive. Initial uranium-series dates from the Bibra and Dampier formations of Shark Bay indicate that both derive from the Late Pleistocene. These numerical ages contradict previous interpretations of relative ages obtained from field studies. The age relationship of the units requires further investigation.

Quaternary Science Reviews↗
USGS1990

Geochemistry of highly fractionated I- and S-type granites from the tin-tungsten province of western Tasmania

The Devonian batholiths of western Tasmania represent a diverse assemblage of highly fractionated intrusions (70 to 77 percent SiO 2 ) that are the products of different source materials. The Housetop batholith exhibits compositional affinities to a fluorine-rich I-type magma. The Meredith batholith also has characteristics indicative of I-type source materials. The Heemskirk batholith is composite, and consists of a volatile (F, B, H 2 O)–rich S-type granite underlying an I-type granite. The Three Hummock Island, Interview River, Sandy Cape, and Conical Rocks plutons probably have an S-type source and are grouped together as the Sandy Cape Suite. Rapakivi texture is common in the Housetop, Meredith, and Heemkirk batholiths. Quartz-tourmaline nodules are found in the Conical Rocks pluton and the S-type portion of the Heemskirk batholith. The Conical Rocks and Interview River plutons yield high initial Sr isotopic ratios of 0.74242 and 0.76009, respectively. The Housetop and Meredith batholiths yield the lowest initial Sr isotopic ratios of 0.71041 and 0.71445, respectively. The S-type portion of the Heemskirk batholith has an initial Sr isotopic ratio of 0.76387. The 40 Ar/ 39 Ar release spectrum and Rb/Sr mineral isochron analyses corroborate previously reported Devonian to Carboniferous age estimates for these batholiths. A relatively low-temperature thermal event (<200°C) caused argon loss from the K-feldspars at about 105 Ma. This heating event is probably related to the continental breakup of Australia from Antarctica. Major-element compositions of the western Tasmanian granites are very similar. The highly fractionated Sandy Cape Suite leucogranites exhibit high Ga/Al ratios typical of A-type granites, but not their extreme Zr, Y, or Ce enrichments. A distinctive feature of the Sandy Cape Suite is the increase in P 2 O 5 concentration with fractionation. The increase in P 2 O 5 with fractionation is apparently due to extremely low Ca activity, which precludes the formation of apatite, thus allowing P 2 O 5 to behave incompatibly in the melt. All of the granitoids have LREE–enriched chondrite-normalized rare earth element patterns. REE fractionation within the individual granitoids can be summarized by two trends: those with LREE >> HREE depletion (Housetop, Meredith, and Heemskirk batholiths), and those with LREE = HREE depletion (Sandy Cape Suite). The first trend is caused by the initial undersaturation of accessory mineral assemblage that resulted from high concentrations of volatiles and/or alkali complexes. The second trend is caused by early saturation of accessory phases and/or refractory accessory phases.

Tasmania↗
USGS1990

Organic tissues, graphite, and hydrocarbons in host rocks of the Rum Jungle Uranium Field, northern Australia

The Rum Jungle Uranium field consists of at least six early Proterozoic deposits that have been mined either for uranium and/or the associated base and precious metals. Organic matter in the host rocks of the Whites Formation and Coomalie Dolomite is now predominantly graphite, consistent with the metamorphic history of these rocks. For nine samples, the mean total organic carbon content is high (3.9 wt%) and ranged from 0.33 to 10.44 wt%. Palynological extracts from the host rocks include black, filamentous, stellate ( Eoastrion -like), and spherical morphotypes, which are typical of early Proterozoic microbiota. The colour, abundance, and shapes of these morphotypes reflect the thermal history, organic richness, and probable lacustrine biofacies of the host rocks. Routine analysis of rock thin sections and of palynological residues shows that mineral grains in some of the host rocks are coated with graphitized organic matter. The grain coating is presumed to result from ultimate thermal degradation of a petroleum phase that existed prior to metamorphism. Hydrocarbons are, however, still present in fluid inclusions within carbonates of the Coomalie Dolomite and lower Whites Formation. The fluid inclusions fluoresce dull orange in blue-light excitation and their hydrocarbon content is confirmed by gas chromatography of whole-rock extracts. Preliminary analysis of the oil suggests that it is migrated, and because it has escaped graphitization through metamorphism it is probably not of early Proterozoic age. The presence of live oil is consistent with fluid inclusion data that suggest subsequent, low-temperature brine migration through the rocks. The present observations support earlier suggestions that organic matter in the host formations trapped uranium to form protore. Subsequent fluid migrations probably brought additional uranium and other metals to these formations, and the organic matter provided a reducing environment for entrapment.

Rum Jungle Uranium Field, northern Australia↗
USGS1989

Solid-state 13C NMR studies of a large fossil gymnosperm from the Yallourn Open Cut, Latrobe Valley, Australia

A series of samples taken from the cross section of a 3-m-diameter fossilized gymnospermous log ( Araucariaceae ) in the Yallourn Seam of the Australian brown coals was examined by solid state 13 C nuclear magnetic resonance to delineate chemical changes related to the combined processes of peatification and coalification. The results show that cellulosic materials were degraded and lost on the periphery of the log, however, the degree of such degradation in the central core is substantially less. The lignin is uniformly altered by coalification reactions to a macromolecular substance displaying decreased aryl ether linkages but significantly greater amounts of carbon linkages compared to modern lignin. Changes in the methoxyl carbon contents of lignin in cross section reveal demethylation reactions, but these do not appear to be related to degree of carbon linking. Both the degredation of cellulosic materials and demethylation of lignin appear to be early diagenetic processes occurring during peatification independently of the coalification reactions.

Latrobe Valley↗
USGS1988

Sedimentology of the Argo and Gascoyne abyssal plains, NW Australia: Report on Ocean Drilling Program Leg 123 (Sept. 1–Nov. 1, 1988)

Ocean Drilling Program Leg 123 drilled two sites in the Indian Ocean in order to study the rifting and early spreading of one of the world’s oldest ocean basins. Site 765 was drilled in 5714 meters of water on the Argo Abyssal Plain northwest of Australia. The sedimentary succession records the opening of an ocean basin, from the first sediments deposited atop young oceanic crust, to the present day. The oldest sediments are microlaminated brown silty claystones, locally rich in calcareous bioclasts. Most of the sequence is dominated by turbidites (primarily calcareous) which probably originated within canyons cut into the margin of the drowned platform of the North West Shelf of Australia. Site 766 is located in 3998 meters of water, at the base of the steep western margin of the Exmouth Plateau. The oldest sediments penetrated are glauconitic, volcaniclastic, and bioclastic sandstones and siltstones, which are interbedded with inclined basaltic sills. These sediments were deposited by a prograding submarine fan system which shed shallow marine sediments westward or northwestward off of the western rim of the Exmouth Plateau. Sandstones are succeeded by silty claystones, recording gradual abandonment or redirection of the fan system. An overlying sequence of pelagic and hemipelagic clayey and zeolitic calcareous oozes and chalks is succeeded by featureless and homogeneous pelagic nannofossil oozes.

Argo abyssal plain, Gascoyne abyssal plain↗
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↗
USGS1987

Liquid carbon dioxide of magmatic origin and its role in volcanic eruptions

Natural liquid carbon dioxide is produced commercially from a 2.5-km-deep well near the 4,500-yr-old maar volcano, Mount Gambier, South Australia. The carbon dioxide has accumulated in a dome that is located on the extension of a linear chain of volcanic activity. A magmatic origin for the fluid is suggested by the geological setting, δ 13 C PDB of –4.0‰, for the CO 2 (where PDB represents the carbon-isotope standard), and a relatively high 3 He component of the contained helium and high 3 He/C ratio (6.4 x 10 −10 ). The 3 He/ 4 He and He/Ne ratios are 3.0 and > 1,370 times those of air, respectively. The CO 2 , as collected at the Earth's surface at 29.5 °C and 75 bar, expands more than 300-fold to form a gas at 1 atm and 22 °C. We suggest that liquid CO 2 or high-density CO 2 fluid (the critical point is 31.1 °C, 73.9 bar) of volcanic origin that expands explosively from shallow levels in the Earth's crust may be a major contributor to 'phreatic' volcanic eruptions and maar formation. Less violent release of magmatic CO 2 into crater lakes may cause gas bursts with equally disastrous consequences such as occurred at Lake Nyos, Cameroon, in August 1986.

Nature↗