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A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa

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Linnemann, Ulf and Pieren, Agustín and Hofmann, Mandy and Drost, Kerstin and Quesada, Cecilio and Gerdes, Axel and Marko, Linda and Gärtner, Andreas and Zieger, Johannes and Ulrich, Jens (2018) A ~565 Ma old glaciation in the Ediacaran of peri-Gondwanan West Africa. International Journal of Earth Sciences, 107 (3). pp. 885-911. ISSN ISSN: 1437-3254, online ISSN: 1437-3262

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Official URL: https://link.springer.com/article/10.1007%2Fs00531-017-1520-7


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Abstract

In the Cadomian orogen of the NE Bohemian Massif and of SW Iberia, a post-Gaskiers glacial event dated at c. 565 Ma has been detected. Such Ediacaran-aged glaciomarine deposits occur in the Weesenstein and Clanzschwitz groups of the Saxo-Thuringian zone (Bohemia) and in the Lower Alcudian group of the southern Central Iberian zone (Iberia). Both areas are parts of Cadomia situated in the Western and Central European Variscides. Glaciomarine sedimentary rocks are characterized by such features as dropstones, flat iron-shaped pebbles (“Bügeleisen-Geschiebe”), facetted pebbles, dreikanters, and zircon grains affected by ice abrasion. For age and provenance determination, LA–ICP–MS U–Pb ages (n = 1124) and Hf isotope (n = 446) analyses were performed. The maximum age of the glaciomarine deposits within a Cadomian back-arc basin based on U–Pb analytics resulted in the youngest detrital zircon populations showing ages of 562–565 Ma and of c. 566–576 Ma old zircon derived from granitoid pebbles within the diamictites. The youngest age recorded was 538–540 Ma based on zircon from the plutons which had intruded the previously deformed Ediacaran metasedimentary rocks. Previously described glaciomarine diamictites of Cadomia (Weesenstein, Clanzschwitz, and Orellana diamictites) are most definitely younger than the c. 579–581 Ma Gaskiers glaciation in Newfoundland (Gaskiers) and in SE New England (Squantum). We propose the term Weesenstein–Orellana glaciation for this new Ediacaran glacial event, named after the most relevant regions of exposure. Palaeogeographically, these glaciomarine diamictites and related sedimentary deposits lie on the periphery of the West African Craton (western peri-Gondwana), and evidence has been provided by detrital zircon U–Pb ages and their Hf isotope composition. Correlation with similar glaciomarine deposits in the Anti-Atlas (Bou Azzer) and Saudi Arabia suggests a continued distribution of post-Gaskiers glacial deposits along the Gondwana margin of Northern Africa. The Weesenstein–Orellana glaciation correlates in part with the Shuram–Wonoka δ13C anomaly.


Item Type:Article
Uncontrolled Keywords:Glaciation, Ediacaran, Weesenstein–Orellana glaciation, Neoproterozoic palaeoclimate, peri-Gondwana, West African craton, Cadomian orogeny, U–Pb zircon ages, Hf isotopes
Subjects:Sciences > Geology > Stratigraphic geology
Sciences > Geology > Geochemistry
ID Code:47352
Deposited On:27 Apr 2018 05:45
Last Modified:11 Dec 2018 08:41

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