Abstract Sedimentary features characteristic of ice-rafting are present in the Bunyeroo Formation (Wilpena Group) of the Adelaide Geosyncline and in the coeval Dey Dey Mudstone (Ungoolya Group) of the eastern Officer Basin (Figs 66.1 & 66.2), providing evidence of a mid-Ediacaran glacial climate in South Australia. The Acraman asteroid impact, a negative shift in marine δ 13 C, and a major acritarch turnover coincided with this frigid epoch.

Abstract The record of two Neoproterozoic glaciations in South Australia has been known for about a century. The earlier glaciation, of Sturtian age, is represented by the Yudnamutana Subgroup and is characterized by widespread diamictites with both intrabasinal and extrabasinal clasts, some locally faceted and striated. Associated facies include shallow-water sandstone, bedded and laminated siltstone with lonestones and dropstones, and sedimentary ironstones (mainly ferruginous siltstone and diamictite). Proximal settings adjacent to the Curnamona Province display massive basement-derived conglomerate and gigantic basement megaclasts (up to hundreds of metres across). Sturtian glaciogenic sediments of the Yudnamutana Subgroup unconformably overlie a variety of older rock units, including crystalline basement near basin margins and uppermost Burra Group sediments in the depocentre, and were deposited both in shallow marine shelf environments and in tectonically active rift basins encircling the Curnamona Province, with corresponding increases in total thickness from 100–300 m to more than 5 km. Recent U–Pb zircon SHRIMP dating of a thin volcaniclastic layer indicates that the waning stages of the Sturtian glaciation occurred at c. 660 Ma. Unlike the deposits of the younger Elatina glaciation, the Yudnamutana Subgroup has so far not yielded reliable palaeomagnetic data.

Abstract Deposits of the late Cryogenian Elatina glaciation constitute the Yerelina Subgroup in the Adelaide Geosyncline region, South Australia. They have a maximum thickness of c . 1500 m, cover 200 000 km 2 , and include the following facies: basal boulder diamictite with penetrative glaciotectonites affecting preglacial beds; widespread massive and stratified diamictites containing faceted and striated clasts, some derived from nearby emergent diapiric islands and others of extrabasinal provenance; laminated siltstone and mudstone with dropstones; tidalites and widespread glaciofluvial, deltaic to marine-shelf sandstones; a regolith of frost-shattered quartzite breccia up to 20 m thick that contains primary sand wedges 3+ m deep and other large-scale periglacial forms; and an aeolian sand sheet covering 25 000 km 2 and containing primary sand wedges near its base. These deposits mark a spectrum of settings ranging from permafrost regolith and periglacial aeolian on the cratonic platform (Stuart Shelf) in the present west, through glaciofluvial, marginal-marine and inner marine-shelf in the central parts of the Adelaide Geosyncline, to outer marine-shelf in sub-basins in the present SE and north. The Elatina glaciation has not been dated directly, and only maximum and minimum age limits of c . 640 and 580 Ma, respectively, are indicated. Palaeomagnetic data for red beds from the Elatina Formation (Fm.) and associated strata indicate deposition of the Yerelina Subgroup within 10° of the palaeoequator. The Yerelina Subgroup is unconformably to disconformably overlain by the dolomitic Nuccaleena Fm., which in most places is the lowest unit of the Wilpena Group and marks Early Ediacaran marine transgression. Supplementary material Photographs are available at http://www.geolsoc.org.uk/SUP18481 .

Abstract: The storm-dominated, high-energy, cool-water Lincoln Shelf occupies the central part of the southern Australian continental margin. Carbonate sediments on this modern distally-steepened ramp were produced by slow deposition during the Terminal Quaternary Sea-level Cycle (0 75 Ka), a high-amplitude, asymmetric cycle of sea-level change. The 50 to 150-mwd (meters water depth), 120-170 km-wide surface is a rocky substrate covered by a patchy, m-scale, palimpsest sediment veneer composed mostly of bryozoans, molluscs, foraminifers and coralline algae. Facies of the condensed Terminal Quaternary Sequence are interpreted to reflect accumulation during different parts of the Terminal Quaternary Sea-level Cycle that are now variably mixed. Accumulation during early stages of the Terminal Quaternary Regression, Isotope Stage-3/4 (IS-3/4), when sea level fluctuated between 30- and at least 60-mwd, took place in a series of shallow marine to paludal environments. Small-scale, 5th-order sea-level fluctuations resulted in recurring deposition, surf-zone reworking and exposure. Such conditions generating Relict Particles, brown- colored, abraded grains filled with carbonate precipitates, that are now concentrated on the middle to inner shelf (< 100-mwd). The Terminal Quaternary Lowstand (early IS-2) at 120-mwd resulted in deposition on the outermost shelf and exposure of the middle and inner shelf. This was a period of mesotrophic conditions and overall upwelling, leading to prolific bryozoan growth and the formation of a bryozoan biostrome at the shelf edge. These conditions continued during the early Terminal Quaternary Transgression (late IS-2) resulting in shelf facies rich in articulated coralline algal particles and rhodolites. Rapid sea-level rise, coupled with a change to more oligotrophic conditions during the late Terminal Quaternary Transgression (early IS-1), drowned these environments and resulted in belts of Stranded Particles on the middle to outer shelf. The modern setting, during the present Terminal Quaternary Highstand, reflects a complex oceanography. Waters are mildly oligotrophic, with yearly incursion of warm, oligotrophic waters from the west, seasonal upwelling of mesotrophic waters and annual outflow of cold, saline bottomwaters from the large shallow embayment of Spencer Gulf. Recent Particles are diverse: bivalves dominate inner-middle shelf sediments; bryozoans are most abundant on the outer shelf; shelf sediments opposite Spencer Gulf saline outflows are rich in benthic foraminifers; and corallines are most abundant inshore. The moribund biostrome is now populated by a rich and diverse suite of deeper water bryozoans and ahermatypic corals. Sediments on the western part of the shelf, with scattered large foraminifers, illustrate the sporadic influence of warmer waters.