Neoproterozoic glacial palaeolatitudes: a global update
D. A. D. Evans, T. D. Raub, 2011. "Neoproterozoic glacial palaeolatitudes: a global update", The Geological Record of Neoproterozoic Glaciations, Emmanuelle Arnaud, Galen P. Halverson, Graham Shields-Zhou
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New stratigraphic, geochronological and palaeomagnetic constraints allow updates to be made to a synthesis of Neoproterozoic glacial palaeolatitudes, including modifications to some reliability estimates. The overall pattern of a Neoproterozoic climatic paradox persists: there is an abundance of tropical palaeolatitudes and near to complete absence of glaciogenic deposits demonstrably laid down between latitudes of 60° and 90°. In addition to 12 units with palaeolatitude estimates that are somewhat reliable, estimates with moderate to high reliability now include Konnarock (less than 10° from the palaeo-equator), Elatina, Rapitan, Mechum River, Grand Conglomerat (10–20°), Upper Tindir, Puga (20–30°), Nantuo, Gaskiers (30–40°) and Walsh (40–50°). Among these, Elatina, Upper Tindir and Nantuo are considered to have the highest reliability, all with estimates of low to moderate palaeolatitude. The Elatina result stems from sedimentary rocks with quantitative correction of inclination-shallowing effects, and the Upper Tindir result stems from data collected from igneous rocks that are precisely coeval with the glacial deposits. Despite continuing debate on the global character of Neoproterozoic ice ages, their pan-glacial extent (ice extending to low latitude in a low-obliquity world) is well demonstrated.
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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.