Risto A. Kumpulainen, 2011. "The Neoproterozoic glaciogenic Lillfjället Formation, southern Swedish Caledonides", The Geological Record of Neoproterozoic Glaciations, Emmanuelle Arnaud, Galen P. Halverson, Graham Shields-Zhou
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The Tossåsfjället Group, which crops out in the Middle Allochthon of the Scandinavian Caledonides, contains the glaciogenic Lillfjället Fm. Evidence that supports the interpretation of the Lillfjället formations as glacially related include the presence of diamictite beds, the presence of lonestones, although few, in laminated units, one possible faceted clast, involution-like deformation structures, and the presence of sandstone wedges cutting 2.5–3 m down into two different diamictite beds. Similar to the other glaciogenic formations in southern and central Scandinavia (Moelv and Långmarkberg formations), the Lillfjället Fm. rests on a unit of peritidal, sabkha-type dolomite of the Storån Fm. Poor exposure contributes to the uncertainty about the thickness of the formation. In this account, the Lillfjället Fm. stratigraphy has been divided into three subunits: (i) a lower diamictite-dominated unit, (ii) a middle unit composed of distinctly laminated grey sandy mudstone and (iii) an upper diamictite-dominated unit. There is no information available from the Tossåsfjället Group concerning palaeolatitudes and chemostratigraphy. Poor isotopic evidence (40Ar/39Ar) from the Ottfjället Dolerites, which cut the Tossåsfjället Group, indicates that the succession is older than c. 665 Ma, so a reliable correlation with global glaciation events is not yet possible.
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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.