The COSC-2 drill core and its well-preserved lower Palaeozoic sedimentary succession – an unexpected treasure beneath the Caledonian nappes
| Autor: | Oliver Lehnert, Bjarne Almqvist, Mark Anderson, Jenny Andersson, Simon Cuthbert, Mikael Calner, Isabel Carter, Riccardo Callegari, Christopher Juhlin, Henning Lorenz, Claudio Madonna, Guido Meinhold, Luca Menegon, Iwona Klonowska, Christophe Pascal, Markus Rast, Nick M. W. Roberts, Jonas B. Ruh, Grzegorz Ziemniak |
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| Jazyk: | angličtina |
| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Estonian Journal of Earth Sciences, Vol 73, Iss 2, Pp 134-140 (2024) |
| Druh dokumentu: | article |
| ISSN: | 1736-4728 1736-7557 |
| DOI: | 10.3176/earth.2024.13 |
| Popis: | The Collisional Orogeny in the Scandinavian Caledonides (COSC) project focuses on processes related to the closure of the Iapetus Ocean, causing the OrdovicianâSilurian continentâcontinent collision between Baltica and Laurentia. The rock succession in the second drill core (COSC-2) from the Jämtland County, central Sweden, provides the base for detailed sedimentological, stratigraphic, geophysical, geochemical, geothermal and structural studies. The basement, comprising 1.66â1.65 Ga Transscandinavian Igneous Belt porphyries intruded by 1.47 Ga and 1.27â1.26 Ga mafic dykes and sills, is heavily weathered towards the top. Here it grades into typical saprock and saprolite (including immature soil reflecting the sub-Cambrian peneplain). The overlying sedimentary sequence starts with basal conglomerates and heterogeneous sediments with shell fragments, indicating an early Cambrian rather than a Neoproterozoic age for the marine transgression in the area. The developing early Cambrian basin was rapidly filled, initially by mostly coarse-grained sediment gravity flows. These strata are covered by sandstone turbidites that show an upward transition into the Alum Shale Formation, representing a tectonically quieter period (mid-Cambrian/Maolingian to Early Ordovician/Tremadocian). The upper part of the Alum Shale Formation is overlain by a late Early Ordovician turbidite succession. Local sources of sediments below the Alum Shale Formation and the extended deposition period may indicate continuous sedimentation in a pull-apart basin preserved in a window beneath the Caledonian thrust sheets. |
| Databáze: | Directory of Open Access Journals |
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