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Peesey Swamp on southern Yorke Peninsula, southern Australia, is a north-northwesterly—south-southeasterly trending lowland depression, approximately 24 km long and 4 to 10 km wide. The richly fossiliferous mollusc and foraminiferal faunal assemblages of the last interglacial Glanville Formation in Peesey Swamp indicate that the paleoenvironment was a low- to medium-energy, sheltered sandflat to shallow-water seaway during the Last Interglacial Maximum (Marine Isotope Substage [MIS] 5e; 128–116 ka). The presence of the fossil bivalve molluscs Katelysia rhytiphora, Chlamys (Equichlamys) bifrons and Fulvia tenuicostata, in life position, indicate that the paleowater depth was ≤4 m in Peesey Swamp. The seaway cut across southern Yorke Peninsula, establishing a marine connection between southern Spencer Gulf and Investigator Strait during deposition of these taxa. Amino acid racemisation dating of the fossil marine molluscs Katelysia sp. and Fulvia tenuicostata confirms that the shelly assemblages at Peesey Swamp are correlative with the last interglacial Glanville Formation, a succession of richly fossiliferous, mixed quartz–skeletal carbonate sands documented from many sites along the southern Australian coastline. This study illustrates the significant changes in the geographical configuration of coastlines that may accompany relatively modest (<5 m) sea-level changes on low-gradient coastal landscapes. Peesey Swamp on southern Yorke Peninsula was flooded by seawater forming a 4 to 10 km-wide seaway during the Last Interglacial Maximum (MIS 5e). Fossil mollusc and foraminiferal assemblages reveal deposition within shallow subtidal to intertidal sandflat environments indicating that the paleowater depth and height of sea-level in Peesey Swamp was ≤4 m. Amino acid racemisation dating of fossil marine molluscs confirms that the shelly assemblages at Peesey Swamp are of last interglacial (MIS 5e) age. The distribution of the foraminifer Marginopora vertebralis indicates that the eastward flow of the warm-water Leeuwin Current, during the Last Interglacial Maximum, was retarded by the biogeographical barriers of Kangaroo Island and Fleurieu Peninsula. [ABSTRACT FROM AUTHOR]

Aim: To determine the effects of competition and divergence time on morphological dissimilarity and geographical range overlap between dasyurid species at both regional and local scales. Our hypothesis is that speciation in this group has been largely allopatric at regional scale, but involved morphological divergence at local scale through sympatric character displacement. Location: Australia, New Guinea and surrounding islands. Taxon: Dasyurid (Dasyuridae) marsupials, 67 species. Methods: Geographical range overlap was quantified using polygons representing the outer limits of species distributions. Local‐scale range overlap was quantified as the degree of co‐occurrence of two taxa across a set of ecological survey plots representing 83 sampled communities. Phylogenies were generated using a novel DNA dataset, with divergence times estimated via total‐evidence dating incorporating fossils. Morphological divergence was determined using body mass and lower molar row length as proxy traits for reconstructing niche exploitation. Results: Sister species pairs were found to be sympatric in 52% (11/21) of cases. Range overlap tended to increase with node age, which supports the hypothesis that mammalian speciation is routinely allopatric. We detected no evidence of character displacement with increasing range overlap between sister species pairs. However, a negative relationship was observed between morphological divergence in body mass and range overlap across all sampled taxa, suggesting that selection in sympatry is convergent, while divergent selection occurs in allopatry. Local‐scale co‐occurrences revealed no trace of species aversion, indicating that competition has not impacted on the spatial distribution of dasyurids. Main conclusions: Despite moderate levels of sympatry through time, our results evince low rates of spatial co‐occurrence between dasyurid species. Although this may be indicative competitive exclusion, the lack of character displacement suggests that biotic interactions have likely not acted as a dominant driver of phenotypic evolution in this radiation. We alternatively posit that abiotic factors including aridity and geographical connectivity have more feasibly propagated character convergence, and led to both niche conservatism and speciation in this ubiquitous australidelphian clade. [ABSTRACT FROM AUTHOR]

The late Carboniferous to Triassic tectonic history of eastern Australia includes important periods of regional-scale crustal extension and contraction. Evidence for these periods of tectonism is recorded by the extensive Pennsylvanian (late Carboniferous) to Triassic basin system of eastern Australia. In this study, we investigate the use of U-Pb dating of detrital zircons in reconstructing the tectonic development of one of these basins, the eastern Galilee Basin of Queensland. U-Pb detrital zircon ages were obtained from samples of stratigraphically well-constrained Cisuralian and Lopingian (early and late Permian, respectively) sandstone in the Galilee Basin. Detrital zircons in these sandstones are dominated by a population with ages in the range of 300-250 Ma, and ages from the youngest detrital zircons closely approximate depositional ages. We attribute these two fundamental findings to (1) appreciable derivation of detrital zircons in the Galilee Basin from the New England Orogen of easternmost Australia and (2) syndepositional magmatism. Furthermore, Cisuralian sandstone of the Galilee Basin contains significantly more >300 Ma detrital zircons than Lopingian sandstone. The transition in detrital zircon population, which is bracketed between 296 and 252 Ma based on previous high-precision U-Pb zircon ages from Permian ash beds in the Galilee Basin, corresponds with the Hunter-Bowen Orogeny and reflects a change in the Galilee Basin from an earlier extensional setting to a later foreland basin environment. During the Lopingian foreland basin phase, the individual depocentres of the Galilee and Bowen basins were linked to form a single and enormous foreland basin that covered >300 000 km2 in central and eastern Queensland. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Gawler Silicic Large Igneous Province (SLIP) in the Gawler Craton and Curnamona Province, southern Australia, comprises extensive felsic and lesser mafic volcanic sequences, with only limited sedimentary successions. The Roopena Basin is a rare example of a synvolcanic sedimentary basin that formed within the Gawler SLIP in the eastern Gawler Craton. It is a north-south-trending basin with a preserved area of 75 km2, bound by the Roopena and Wizzo Well faults, and contains three units of the lower Gawler Range Volcanics; the Angle Dam Dacite, Fresh Well Formation and Roopena Basalt. The Angle Dam Dacite is a porphyritic lava and the oldest part of the volcanic succession, directly overlying basement. The Fresh Well Formation overlies the Angle Dam Dacite or basement, comprises three coarsening-upwards volcaniclastic packages of claystone, siltstone, fine-grained to coarse-grained lithic sandstone and conglomerate deposited in a fluvio-lacustrine setting, and contains three tuff members. The Roopena Basalt is interlayered with the Fresh Well Formation, and comprises auto-brecciated lavas that exhibit only local interaction with water or wet sediment. Sharp basal contacts of the prograding packages within the Fresh Well Formation provide evidence of rapid flooding events within the basin. New detrital zircon geochronology of a sandstone within the Fresh Well Formation yielded a maximum depositional age of ca 1580 Ma, with provenance dominated by felsic volcanic units of the 1635-1605 Ma St Peter Suite. Sedimentation in the Gawler SLIP appears to have occurred in isolated basins with limited areal extent. It was largely restricted to the eastern Gawler Craton, and as well as the Roopena Basin, and includes similar basins at the Olympic Dam and Prominent Hill iron oxide-copper-gold ± uranium (IOCG ± U) deposits. The coincidence of sedimentation and mafic volcanism in the eastern Gawler Craton suggests that this region underwent extension at this time, although high-temperature metamorphism and compressional deformation occurred in some parts of the Gawler Craton and Curnamona Province synchronous with the Gawler SLIP. The Roopena Basin sedimentary rocks and underlying basement contain hematite-chlorite-sericite-white mica assemblages, permissive of hematite-style IOCG mineral deposits; however, no significant ore deposit has yet been discovered in the Roopena Basin. [ABSTRACT FROM AUTHOR]

A new compilation of historical observations and archaeomagnetic measurements of magnetic inclination for the last 1000 years from eastern Australia (the eastern Australian Inclination Record [eAIR2012]) has revealed the existence of a well-defined inclination anomaly in the region. Evidence of this magnetic feature has been preserved in sedimentary records from across eastern Australia, though this has not previously been recognised. Analyses of additional sedimentary sequences have confirmed the incidence and timing of this feature, revealing its presence between the 13th and 18th centuries ad. The inclination of the field during this episode appears to have been steeper than at any time since the start of the Holocene. Lake sediment evidence suggests that the anomaly is a composite feature, displaying a distinct peak at cal. ad 1270–1386 (±2 σ uncertainty), reappearing after cal. ad 1431–1651 (±2 σ uncertainty) and disappearing before cal. ad 1822±46 (±2 σ uncertainty). The disappearance of the anomaly is tightly bracketed in the historical record between ad 1770 and 1777. The rapid shift in inclination during the 18th century ad offers considerable potential as a means of dating a critical period of Australian environmental history, an episode that currently lies beyond the reach of established dating methods. This information also provides a valuable constraint on models of regional geomagnetic field change over centennial and millennial timescales. Our examination of the historical record has revealed that the inclination measurements made by the 18th-century French explorer La Pérouse are consistently erroneous. Since La Pérouse’s data make up 13% of the total body of pre-19th century inclination records, the inclusion of these measurements in global compendia of magnetic observations may seriously skew attempts to model the geomagnetic field. We advocate that La Pérouse’s inclination measurements should therefore be employed only with considerable caution. [ABSTRACT FROM PUBLISHER]

Geologic and chronometric studies of alluvial fan sequences in south-central Australia provide insights into the roles of tectonics and climate in continental landscape evolution. The most voluminous alluvial fans in the Flinders Ranges region have developed adjacent to catchments uplifted by Plio-Quaternary reverse faults, implying that young tectonic activity has exerted a first-order control on long-term sediment accumulation rates along the range front. However, optically stimulated luminescence (OSL) dating of alluvial fan sequences indicates that late Quaternary facies changes and intervals of sediment aggradation and dissection are not directly correlated with individual faulting events. Fan sequences record a transition from debris flow deposition and soil formation to clast-supported conglomeritic sedimentation by ∼30 ka. This transition is interpreted to reflect a landscape response to increasing climatic aridity, coupled with large flood events that episodically stripped previously weathered regolith from the landscape. Late Pleistocene to Holocene cycles of fan incision and aggradation post-date the youngest-dated surface ruptures and are interpreted to reflect changes in the frequency and magnitude of large floods. These datasets indicate that tectonic activity controlled long-term sediment supply but climate governed the spatial and temporal patterns of range-front sedimentation. Mild intraplate tectonism appears to have influenced Plio-Quaternary sedimentation patterns across much of the southern Australian continent, including the geometry and extent of alluvial fans and sea-level incursions. [ABSTRACT FROM AUTHOR]

Discusses the idea that manganese oxides in association with paleoweathering can offer insight into the factors affecting the formation and evolution of weathering profiles. Finding from laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia; Indication the plateaus and consistent isochron ages confirm the feasibility dating of supergene manganese oxides by the 40Ar/39Ar technique; Identification of two distinct structural sites hosting Ar isotopes; Mention of degassing behaviors discovered by incremental heating analyses; Assertion there is no significant Ar gas released at laser power higher than 1.0 W, which suggests the breakdown of tunnel sites hosting the radiogenic and nucleogenic components; Suggestion that some isotopes occupy crystallographic sites; Evidence that 39ArK loss from the tunnel site during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur; Assertion that neither the overwhelming atmospheric 40Ar nor the very-fined nature of the supergene manganese oxides will be a problem in extracting significant information from the analysis of supergene manganese oxides minerals.

Rocks from the Sulphur Springs Group, a newly identified stratigraphic succession hosting volcanogenic massive sulphide (VMS) base-metal deposits in the Soanesville Belt, Pilbara Craton, northwestern Australia, have been analyzed by sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon mass-spectrometry to determine their age and tectonostratigraphic relationships. Most volcanism occurred between 3238 and 3235 Ma, distinctly different from the time interval spanned by the Wyman Formation (type section is 3315 Ma, other dates ∼3325 Ma) with which it was previously correlated. Outlying volcanic rocks with similar geochemistry at the Bernts and Obelix prospects also produce dates from 3240 to 3235 Ma and are, therefore, best interpreted as structurally-detached fragments of the Sulphur Springs Group. The Strelley Granite, an intrusion which shares geochemical characteristics with the overlying volcanic rocks, also yields similar ages, thus extending the period of temporally-linked extrusive–intrusive silicic magmatism in the evolution of the Pilbara Craton. Model Pb–Pb dating of galena from the Zn–Cu mineralization at the various VMS prospects has yielded ages consistent with the zircon U–Pb ages of the host rocks, indicating that the hydrothermal mineralizing systems were contemporaneous with and apparently initiated by igneous activity. An epicontinental tectonic setting for the Sulphur Springs Group during VMS mineralization is implied by the broad range of old zircon ages obtained from a tuff at the base of the volcanic pile. As the igneous episode coincides with the peak regional metamorphic event recorded in other east Pilbara supracrustal rocks and with voluminous intrusive activity in nearby granitoid complexes, it marks a major event in the crustal evolution of the eastern Pilbara Craton. [Copyright &y& Elsevier]

A new radiometric date of 3.6 Ma for the basalt overlying fossiliferous units of the Allingham Formation, provides a minimum age for the Bluff Downs Local Fauna. Ground studies and interpretation of aerial photography has clarified the volcanic history of the area and a new basalt flow has been identified and named. Although the age of the capping basalt permits a younger age for the Bluff Downs Local Fauna than originally described, the stratigraphy,combined with the interpreted stage of evolution of the fauna, still supports an Early Pliocene age for the site. [ABSTRACT FROM AUTHOR]

The age of the Ashburton Province, comprising an older divergent-margin megasequence and a younger convergent-margin megasequence, is poorly constrained. The Boolaloo Granodiorite, which intruded the divergent-margin megasequence on the western margin of the Ashburton Province, has given a SHRIMP zircon U–Pb age of 1786 ± 5 Ma, and therefore post-dates convergent-margin, backarc basin sequences, with established conventional zircon U–Pb ages of ca 1843–1828 Ma. However, it pre-dated deformation of convergent-margin, remnant-ocean sequences. Similarly aged (ca 1797–1791 Ma) granitoids are present in the adjacent Gascoyne Province, thereby identifying a magmatic fold-thrust belt that abutted a remnant ocean in the Ashburton Province. [ABSTRACT FROM AUTHOR]

Examines the geochronology of supracrustal from the Golden Grove area of Murchison Province, Yilgran Craton, Western Australia. Division of the domains of Yilgran Craton; Recognition of the stratigraphic units; Geology of the Warriedar Fold Belt.