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 basal Ediacaran global boundary stratotype section and point (GSSP) horizon beneath Nuccaleena Formation cap dolostone in South Australia's central Flinders Ranges South Australia coincides with an interpreted unconformity preceding deglacial transgression. Detailed lithostratigraphy of three sections across the base of the Ediacaran System at its type area reveals contrasting character of the Elatina Formation—Nuccaleena Formation transition across c . 9 km of exposure, changing the interpretive context of the GSSP. We suggest that a locally pervasive, incisive flaser-bedded sandstone exposed between Elatina diamictites and Nuccaleena cap dolostone lies above an unconformity that correlates with the defined base of Wilpena Group, reflecting onset of terminal Elatina ‘Snowball Earth’ deglaciation and dynamic interplay between eustatic sea level change and isostatic rebound. Nuccaleena cap dolostone is sedimentologically mixed and conformable with underlying siliciclastics at Elatina Creek; hence the recently defined Ediacaran GSSP horizon, at the base of solid cap carbonate at Enorama Creek, lies in continuous section and not at an unconformity. Nuccaleena Formation cap dolostone contains pervasive terrigenous debris, including apparently detrital hematite. While magnetite and/or maghemite is produced in abundance upon heating of the cap carbonate above c . 400°C, and we cannot exclude secondary origin of any Nuccaleena magnetite, Nuccaleena Formation cap dolostone should preserve primary magnetization.