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The COSC-2 drill core and its well-preserved lower Palaeozoic sedimentary succession – an unexpected treasure beneath the Caledonian nappes

Lehnert, Oliver LU ; Almqvist, Bjarne ; Anderson, Mark ; Andersson, Jenny ; Cuthbert, Simon ; Calner, Mikael LU orcid ; Carter, Isabel ; Callegari, Riccardo ; Juhlin, Christopher and Lorenz, Henning , et al. (2024) In Estonian Journal of Earth Sciences 73(2). p.134-140
Abstract

The Collisional Orogeny in the Scandinavian Caledonides (COSC) project focuses on processes related to the closure of the Iapetus Ocean, causing the Ordovician–Silurian continent– continent 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 1.66–1.65 Ga Transscandinavian Igneous Belt porphyries intruded by 1.47 Ga and 1.27–1.26 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).... (More)

The Collisional Orogeny in the Scandinavian Caledonides (COSC) project focuses on processes related to the closure of the Iapetus Ocean, causing the Ordovician–Silurian continent– continent 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 1.66–1.65 Ga Transscandinavian Igneous Belt porphyries intruded by 1.47 Ga and 1.27–1.26 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.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
Baltica, Caledonian Orogen, Cambrian, ICDP, Ordovician, Scandinavian Caledonides (COSC), Sweden
in
Estonian Journal of Earth Sciences
volume
73
issue
2
pages
7 pages
publisher
Estonian Academy Publishers
external identifiers
  • scopus:85208604776
ISSN
1736-4728
DOI
10.3176/earth.2024.13
language
English
LU publication?
yes
id
0383791e-35e5-4b5d-b245-33952c594851
date added to LUP
2025-02-18 08:34:06
date last changed
2025-04-04 14:19:25
@article{0383791e-35e5-4b5d-b245-33952c594851,
  abstract     = {{<p>The Collisional Orogeny in the Scandinavian Caledonides (COSC) project focuses on processes related to the closure of the Iapetus Ocean, causing the Ordovician–Silurian continent– continent 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 1.66–1.65 Ga Transscandinavian Igneous Belt porphyries intruded by 1.47 Ga and 1.27–1.26 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.</p>}},
  author       = {{Lehnert, Oliver and Almqvist, Bjarne and Anderson, Mark and Andersson, Jenny and Cuthbert, Simon and Calner, Mikael and Carter, Isabel and Callegari, Riccardo and Juhlin, Christopher and Lorenz, Henning and Madonna, Claudio and Meinhold, Guido and Menegon, Luca and Klonowska, Iwona and Pascal, Christophe and Rast, Markus and Roberts, Nick M.W. and Ruh, Jonas B. and Ziemniak, Grzegorz}},
  issn         = {{1736-4728}},
  keywords     = {{Baltica; Caledonian Orogen; Cambrian; ICDP; Ordovician; Scandinavian Caledonides (COSC); Sweden}},
  language     = {{eng}},
  number       = {{2}},
  pages        = {{134--140}},
  publisher    = {{Estonian Academy Publishers}},
  series       = {{Estonian Journal of Earth Sciences}},
  title        = {{The COSC-2 drill core and its well-preserved lower Palaeozoic sedimentary succession – an unexpected treasure beneath the Caledonian nappes}},
  url          = {{http://dx.doi.org/10.3176/earth.2024.13}},
  doi          = {{10.3176/earth.2024.13}},
  volume       = {{73}},
  year         = {{2024}},
}