Neoproterozoic glaciated basins: a critical review ofthe Snowball Earth hypothesis by comparison withPhanerozoic glaciations

摘要

The Neoproterozoic is widely considered to have experienced some of the most severe climaticperturbations recorded in Earth history, with extensive glaciations often referred to as 'SnowballEarth' events. The Snowball Earth and competing hypotheses seek to explain a wide range of geo-logical data on Neoproterozoic pre-, syn- and post-glacial successions including glacial sedimentology,chemostratigraphy, palaeoceanography, geochronology, palaeomagnetism and palaeogeography,geodynamics, tectonics, palaeontology and palaeobiogeochemistry. However, our understandingof the Phanerozoic and particularly the Cenozoic and contemporary glacial geological record isoften relatively neglected when evaluating the evidence for apparent severe and prolonged periodsof globally synchronous glaciation. This paper presents a review of the available geological data forNeoproterozoic glacial successions in the light of what we know about the Cenozoic and recentglacial record. Most Neoproterozoic successions are shown to exhibit spatial and temporal vari-ability, with sediment stacking patterns and facies associations indicative of dynamic ice masses.These characteristics are typical of sedimentary sequences deposited along glaciated continentalmargins throughout Earth history, without the need for global synchroneity or necessarily severeclimatic excursions. Although recurrent very widespread glaciation is envisaged in the Neopro-terozoic, the presence of analogous glacigenic and interglacial successions in the Neoproterozoicand Cenozoic suggest the operation of a similar set of processes across a similar range of deposi-tional environments. Consequently, an unambiguous sedimentary record of hydrological shutdownduring a prolonged global glaciation appears to be lacking. This indicates either a preservationalbias in Neoproterozoic successions of the advance and recessional stages of glacial epochs, or theoccurrence of dynamic, non-global glaciations during the Neoproterozoic.