An interval several hundred metres thick in the lower part of the late Ediacaran Billy Springs Formation (Fm.) of the NE Flinders Ranges, South Australia, includes both diamictic levels, ‘dropstones’ and isolated ‘stone-clusters’ in a thin-bedded, silty or fine sandy matrix, which is commonly laminated. Slumping at a variety of scales is prevalent, but extensive panels of ‘right-way-up’, moderately dipping beds host dropstones, which disturbed the laminae. It is difficult to explain laminated sediments peppered with dropstones other than by ice-rafting, and the stone-clusters comply with sinking pieces of ice loaded with debris. Although common reworking occurred in channels, larger erratics in this material are out of hydrodynamic equilibrium. Deposition occurred offshore on an unstable slope.
Isotopic δ13Ccarb measurements show a strong negative excursion through the preceding Wonoka Fm., and several further similar negative excursions in the Billy Springs Fm. This record shows similarities to that of Ediacaran carbonates on the Yangtze platform, south China. Compilation based on a survey of palaeomagnetic data for Gondwana continents, Baltica and Laurasia permits a possible palaeogeography indicating a relatively high palaeolatitude at the time of deposition. Indications of age are imprecise but may be comparable with, or younger(?) than the c. 580 Ma Gaskiers Fm. of Newfoundland.
Figures & Tables
The Geological Record of Neoproterozoic Glaciations
In recent years, interest in Neoproterozoic glaciations has grown as their pivotal role in Earth system evolution has become increasingly clear. One of the main goals of the IGCP Project No. 512 was to produce a synthesis of newly available information on Neoproterozoic successions worldwide similar in format to Hambrey & Harland’s (1981) Earth’s pre-Pleistocene Glacial Record. This Memoir therefore consists of a series of overview chapters followed by site-specific chapters. The overview chapters cover key topics including the history of research on Neoproterozoic glaciations, identification of glacial deposits, chemostratigraphic techniques and datasets, palaeomagnetism, biostratigraphy, geochronology and climate modelling. The site specific chapters for 60 successions worldwide include reviews of the history of research on these rocks and up-to-date syntheses of the structural framework, tectonic setting, palaeomagnetic and geochronological constraints, physical, biological, and chemical stratigraphy, and descriptions of the glaciogenic and associated strata, including economic deposits.