The Paleoproterozoic Grythyttan Field in the Svecofennian Orogen, West Bergslagen, Central Sweden: Structure, Stratigraphy and Age.

F.F. Beunk, Gerrit Kuipers, Keewook Yi, Frederik van der Wateren

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

A number of discrete slate belts of limited size occur in the Paleoproterozoic volcano-sedimentary Bergslagen Group of western Bergslagen in the Fennoscandian shield of south central Sweden. The Grythyttan Slate Belt, studied for more than a century, forms a single basin with the nearby Saxån Slate Belt. We use the lithostratigraphy of the Grythyttan Slate Formation of the Grythyttan belt, based on basin scale sedimentary facies associations of the volcaniclastic sediments in time and space, as a method to interpret overall tectonic structure. Contrary to traditional views, we reconstruct the GSB as a single overturned limb of a km-scale anticline with horizontal axis in the hanging wall of an east vergent thrust fault, reactivating a listric extensional fault. The fold connects the GSB to the neighboring SSB. Folding and thrusting were related to tectonic closure of a volcanic back- or intra-arc basin. The early folds were subsequently affected by strike-slip shearing and folding around vertical fold axes, which partitioned preferentially into the least competent lithologies (slates and marbles), significantly modifying the map appearance of the slate belt. The late shearing and folding resulted from accretion of Bergslagen onto the Fennoscandian continental margin during the late, Svecobaltic phase of the Svecofennian orogeny. The GSB forms a thin, intraformational wedge in the Bergslagen Group and represents a relatively short interlude with a conglomeratic alluvial fan and turbiditic volcaniclastics followed by more felsic volcanic rocks resembling those of the Bergslagen Group. We suggest that the GSB, and by inference the other slate belts, stem from calderas, as either terrestrial volcanic lakes or shallow submarine eruption centers. The conglomerates are pre-orogenic, not a post-orogenic molasse, as traditionally conceived, and their clast fabric has resulted from sedimentary processes only. Newly determined SIMS U-Pb zircon ages constrain the age of the GSB at ca. 1895 Ma.
Original languageEnglish
Pages (from-to)33-57
Number of pages25
JournalNorwegian journal of geology
Volume98
Issue number3
DOIs
Publication statusPublished - 2018

Fingerprint

Svecofennian
slate
stratigraphy
folding
fold
Svecofennian orogeny
basin
molasse
lithostratigraphy
tectonic structure
felsic rock
hanging wall
thrust fault
alluvial fan
anticline
marble
caldera
clast
conglomerate
limb

Keywords

  • Paleoproterozoic, structure, stratigraphy, geochronology, Bergslagen, Sweden

Cite this

@article{10783cda5b9a49c8a30ab389c9f8bf59,
title = "The Paleoproterozoic Grythyttan Field in the Svecofennian Orogen, West Bergslagen, Central Sweden: Structure, Stratigraphy and Age.",
abstract = "A number of discrete slate belts of limited size occur in the Paleoproterozoic volcano-sedimentary Bergslagen Group of western Bergslagen in the Fennoscandian shield of south central Sweden. The Grythyttan Slate Belt, studied for more than a century, forms a single basin with the nearby Sax{\aa}n Slate Belt. We use the lithostratigraphy of the Grythyttan Slate Formation of the Grythyttan belt, based on basin scale sedimentary facies associations of the volcaniclastic sediments in time and space, as a method to interpret overall tectonic structure. Contrary to traditional views, we reconstruct the GSB as a single overturned limb of a km-scale anticline with horizontal axis in the hanging wall of an east vergent thrust fault, reactivating a listric extensional fault. The fold connects the GSB to the neighboring SSB. Folding and thrusting were related to tectonic closure of a volcanic back- or intra-arc basin. The early folds were subsequently affected by strike-slip shearing and folding around vertical fold axes, which partitioned preferentially into the least competent lithologies (slates and marbles), significantly modifying the map appearance of the slate belt. The late shearing and folding resulted from accretion of Bergslagen onto the Fennoscandian continental margin during the late, Svecobaltic phase of the Svecofennian orogeny. The GSB forms a thin, intraformational wedge in the Bergslagen Group and represents a relatively short interlude with a conglomeratic alluvial fan and turbiditic volcaniclastics followed by more felsic volcanic rocks resembling those of the Bergslagen Group. We suggest that the GSB, and by inference the other slate belts, stem from calderas, as either terrestrial volcanic lakes or shallow submarine eruption centers. The conglomerates are pre-orogenic, not a post-orogenic molasse, as traditionally conceived, and their clast fabric has resulted from sedimentary processes only. Newly determined SIMS U-Pb zircon ages constrain the age of the GSB at ca. 1895 Ma.",
keywords = "Paleoproterozoic, structure, stratigraphy, geochronology, Bergslagen, Sweden",
author = "F.F. Beunk and Gerrit Kuipers and Keewook Yi and {van der Wateren}, Frederik",
year = "2018",
doi = "10.17850/njg98-3-05",
language = "English",
volume = "98",
pages = "33--57",
journal = "Norwegian journal of geology",
issn = "0029-196X",
publisher = "Geological Society of Norway",
number = "3",

}

The Paleoproterozoic Grythyttan Field in the Svecofennian Orogen, West Bergslagen, Central Sweden: Structure, Stratigraphy and Age. / Beunk, F.F.; Kuipers, Gerrit; Yi, Keewook; van der Wateren, Frederik.

In: Norwegian journal of geology, Vol. 98, No. 3, 2018, p. 33-57.

Research output: Contribution to JournalArticleAcademicpeer-review

TY - JOUR

T1 - The Paleoproterozoic Grythyttan Field in the Svecofennian Orogen, West Bergslagen, Central Sweden: Structure, Stratigraphy and Age.

AU - Beunk, F.F.

AU - Kuipers, Gerrit

AU - Yi, Keewook

AU - van der Wateren, Frederik

PY - 2018

Y1 - 2018

N2 - A number of discrete slate belts of limited size occur in the Paleoproterozoic volcano-sedimentary Bergslagen Group of western Bergslagen in the Fennoscandian shield of south central Sweden. The Grythyttan Slate Belt, studied for more than a century, forms a single basin with the nearby Saxån Slate Belt. We use the lithostratigraphy of the Grythyttan Slate Formation of the Grythyttan belt, based on basin scale sedimentary facies associations of the volcaniclastic sediments in time and space, as a method to interpret overall tectonic structure. Contrary to traditional views, we reconstruct the GSB as a single overturned limb of a km-scale anticline with horizontal axis in the hanging wall of an east vergent thrust fault, reactivating a listric extensional fault. The fold connects the GSB to the neighboring SSB. Folding and thrusting were related to tectonic closure of a volcanic back- or intra-arc basin. The early folds were subsequently affected by strike-slip shearing and folding around vertical fold axes, which partitioned preferentially into the least competent lithologies (slates and marbles), significantly modifying the map appearance of the slate belt. The late shearing and folding resulted from accretion of Bergslagen onto the Fennoscandian continental margin during the late, Svecobaltic phase of the Svecofennian orogeny. The GSB forms a thin, intraformational wedge in the Bergslagen Group and represents a relatively short interlude with a conglomeratic alluvial fan and turbiditic volcaniclastics followed by more felsic volcanic rocks resembling those of the Bergslagen Group. We suggest that the GSB, and by inference the other slate belts, stem from calderas, as either terrestrial volcanic lakes or shallow submarine eruption centers. The conglomerates are pre-orogenic, not a post-orogenic molasse, as traditionally conceived, and their clast fabric has resulted from sedimentary processes only. Newly determined SIMS U-Pb zircon ages constrain the age of the GSB at ca. 1895 Ma.

AB - A number of discrete slate belts of limited size occur in the Paleoproterozoic volcano-sedimentary Bergslagen Group of western Bergslagen in the Fennoscandian shield of south central Sweden. The Grythyttan Slate Belt, studied for more than a century, forms a single basin with the nearby Saxån Slate Belt. We use the lithostratigraphy of the Grythyttan Slate Formation of the Grythyttan belt, based on basin scale sedimentary facies associations of the volcaniclastic sediments in time and space, as a method to interpret overall tectonic structure. Contrary to traditional views, we reconstruct the GSB as a single overturned limb of a km-scale anticline with horizontal axis in the hanging wall of an east vergent thrust fault, reactivating a listric extensional fault. The fold connects the GSB to the neighboring SSB. Folding and thrusting were related to tectonic closure of a volcanic back- or intra-arc basin. The early folds were subsequently affected by strike-slip shearing and folding around vertical fold axes, which partitioned preferentially into the least competent lithologies (slates and marbles), significantly modifying the map appearance of the slate belt. The late shearing and folding resulted from accretion of Bergslagen onto the Fennoscandian continental margin during the late, Svecobaltic phase of the Svecofennian orogeny. The GSB forms a thin, intraformational wedge in the Bergslagen Group and represents a relatively short interlude with a conglomeratic alluvial fan and turbiditic volcaniclastics followed by more felsic volcanic rocks resembling those of the Bergslagen Group. We suggest that the GSB, and by inference the other slate belts, stem from calderas, as either terrestrial volcanic lakes or shallow submarine eruption centers. The conglomerates are pre-orogenic, not a post-orogenic molasse, as traditionally conceived, and their clast fabric has resulted from sedimentary processes only. Newly determined SIMS U-Pb zircon ages constrain the age of the GSB at ca. 1895 Ma.

KW - Paleoproterozoic, structure, stratigraphy, geochronology, Bergslagen, Sweden

U2 - 10.17850/njg98-3-05

DO - 10.17850/njg98-3-05

M3 - Article

VL - 98

SP - 33

EP - 57

JO - Norwegian journal of geology

JF - Norwegian journal of geology

SN - 0029-196X

IS - 3

ER -