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Alluvial-channel and overlying eolian deposits exposed in coastal cliffs in the Port Campbell australite (Australian tektite) strewn field, SW Victoria, were studied stratigraphically and dated by optically stimulated luminescence (OSL) for quartz sand grains to illuminate the occurrence of australites in this area. The channel deposits, termed the Dog Trap Bay Sand, yielded OSL ages from 420 ± 40 to 230 ± 15 ka for four sites, and the two eolian units OSL ages of 203 ± 16 and 93 ± 11 ka. The ages support field evidence that, contrary to the conclusions of a previous study by others, the channel deposits are stratigraphically distinct from and much younger than the Pliocene Hanson Plain Sand, which forms a regionally extensive system of marine strandlines to the north and NE of Port Campbell. The OSL ages show some preference for times of negative temperature anomalies marking the last four glacial periods of the Middle and Late Pleistocene as indicated by ice-core data from Antarctica. Eolian and at leas...

Isolated quartzose pebbles, clusters of quartz granules, orthogonal aggregates of poorly sorted quartzose coarse sand, and ovoid pellets (≤2 mm long) of quartz silt occur in hemipelagic marine mudstone of the mid-Ediacaran Bunyeroo Formation exposed in the Adelaide Geosyncline (Adelaide Rift Complex), and ovoid pellets of quartz silt in cores of the correlative marine Dey Dey Mudstone from deep drillholes in the Officer Basin, South Australia. This detritus is interpreted respectively as dropstones, dumps, and frozen aggregates dispersed by sea ice possibly of seasonal origin, and till pellets transported by glacial ice. The ice-rafted material in the Bunyeroo Formation only has been found 500 km northwest of ...

The Holocene carbonate sequence of perennial North Stromatolite Lake, located adjacent to the Coorong Lagoon near Salt Creek, South Australia, includes a prominent sapropelic unit (7 – 12% total organic carbon), in places more than 2 m thick, that was sampled for the purpose of radiocarbon dating and documenting its diatom and ostracod biostratigraphy. The recovered ostracods were also subjected to carbon and oxygen isotopic analysis. The bulk organic matter at the base of the sapropel yielded an uncalibrated 14C age of 6080 ± 60 y BP. Diatoms, where preserved, are almost exclusively benthic. Stratigraphic variation of the proportions of key indicator species in diatom assemblages records a marked oscillation between oligosaline and eusaline conditions in the hypolimnion during deposition of the sapropel. Ostracod carbon isotope data indicate that the lake at this time was eutrophic, thereby enriching the dissolved inorganic carbon of the hypolimnion in 13C. However, the observed secular variation in δ13C...

Multidisciplinary research during the past 25 years has established that the Acraman impact structure in the 1.59 Ga Gawler Range Volcanics on the Gawler Craton, and an ejecta horizon found 240 – 540 km from Acraman in the ⩽ 580 Ma Bunyeroo Formation in the Adelaide Fold Belt and Dey Dey Mudstone in the Officer Basin, record a Late Neoproterozoic (Ediacaran) event of major environmental importance. Research since 1995 has verified Acraman as a complex impact structure that has undergone as much as 3 – 5 km of denudation and which originally had a transient cavity up to 40 km in diameter and a final structural rim possibly 85 – 90 km in diameter. The estimated impact energy of 5.2 × 106 Mt (TNT) for Acraman exceeds the threshold of 106 Mt nominally set for global catastrophe, and the impact probably caused a severe perturbation of the Ediacaran environment. The occurrence of the impact at a low palaeolatitude (12.5 + 7.1/ − 6.1°) may have magnified the environmental effects by perturbing the atmosphere in ...

New occurrences of the Acraman impact ejecta layer were recently discovered in two drillholes, Giles 1 and Murnaroo 1, in the eastern Officer Basin, South Australia, using acritarch biostratigraphy and lithostratigraphy to predict the position. Fractured crystals were also observed in palynological preparations from drillhole SCYW 1a on the Stuart Shelf. These discoveries improve stratigraphic control of Late Neoproterozoic successions, especially in the eastern Officer Basin and will allow a test of the hypothesis that the Acraman impact event caused a global catastrophe.

It appears that differences in the signature of biogenic components and cements under cathodoluminescence may aid in the determination of palaeoenvironments in coastal areas. Living and recently dead aragonitic gastropods (Coxiella spp.) from Old Man Lake sediments luminesce bright apple‐green whereas the same species from the nearby saline environment of the Coorong Lagoon shows no luminescence. Following diagenetic alteration to calcite, as confirmed by X‐ray diffraction analysis, the gastropods show characteristic orange cathodoluminescence in both environments.

Holocene sediments from southern Spencer Gulf are cool‐water carbonate‐rich gravels and sands, dominated by molluscs and Bryozoa. Five sedimentary fades are recognized: (i) molluscan gravel; (ii) branching coralline‐algal gravel, associated with shallow partially protected environments; (iii) molluscan‐biyozoan sand; (iv) mixed bioclastic sand, representative of the deeper central region of the lower gulf; and (v) bryozoan gravel, an isolated fades developed in a semi‐protected micro‐environment. The southern gulf is characterized by complex oceanographic conditions together with variations in water depth and substrate. The sediments share the characteristics of both the southern shelf and upper Spencer Gulf. Grain‐size distribution and sedimentary facies are controlled by a combination of all the above processes. Past sea level fluctuations are recognized from sea floor strand‐line deposits. The relic component of the palimpsest sediments has eroded from the Pleistocene aeolianite dunes. The sediments, t...

Benthic foraminifera are abundant in surficial sediment of Gulf St Vincent and the distribution of many species is related to water depth. For example, Nubecularia lucifuga is most abundant in shallow northern waters while Ammobaculites reophaciformis is more common in deeper southern parts of the gulf. Elphidium crispum, a shallow‐water species, and E. macelliforme, favouring deeper water, provide a useful numerical ratio. Their logarithmic relative abundance in the sediment size fraction 0.50–0.25 mm correlates closely with water depth, particularly for southern Gulf St Vincent. Vibrocore SV23 recovered an undisturbed section of Quaternary strata from one of the deepest parts (40 m) of the gulf. Late Pleistocene sediment (oxygen isotope stage 3) was in turn overlain by rapidly deposited lacustrine and restricted marginal marine sediment before development of more open Holocene marine conditions. Using the Elphidium ratios and other supporting foraminiferal data on a framework of 14C dates, a palaeosea‐l...

The U‐Pb ages of zircons from a tuff‐like layer in the Late Precambrian Bunyeroo Formation in the central and southern Flinders Ranges, South Australia, show that the layer was not formed from volcanic detritus contemporaneous with sedimentation. The ages, dominantly 1575 ± 11 Ma, are consistent with the layer having been derived largely from the Gawler Range Volcanics. On this and other evidence, the layer has been identified as the ejecta blanket from a large bolide impact (Gostin et al 1986). Zircons from a second tuff‐like layer in the Bunyeroo Formation from the northern Flinders Ranges are dominantly much younger, 1143 ± 26 Ma, and have been abraded by sedimentary processes, indicating that that layer is not part of the same blanket.

(1989). Geological Note: Discovery of the acraman impact ejecta blanket in the officer basin and its stratigraphic significance. Australian Journal of Earth Sciences: Vol. 36, No. 4, pp. 585-587.