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Subaerial speleothems and deep karst in central Sweden linked to Hirnantian glaciations

Kroger, Bjorn; Ebbestad, Jan Ove R.; Lehnert, Oliver LU ; Ullmann, Clemens V.; Korte, Christoph; Frei, Robert and Rasmussen, Christian LU (2015) In Journal of the Geological Society 172(3). p.349-356
Abstract
The limestones of the upper Katian Boda mud mounds (Ordovician) of the Siljan district in central Sweden are deeply fractured. The fissures were partly synsedimentary and are often lined with stromatolite-like crusts. These crusts thus far are the only known subaerial Ordovician speleothems. They reach depths of up to 30 m below the former mound top. Macroscopically the crusts form decimetre-sized, cone-shaped domal aggregates, stalactites and stalagmites. Microfabric and morphology identify them as microbially mediated speleothems in a dark environment. Combined Sr and C isotope values indicate a formation of the speleothems from meteoric waters without influence of a significant soil horizon. For the first time the age of the speleothems... (More)
The limestones of the upper Katian Boda mud mounds (Ordovician) of the Siljan district in central Sweden are deeply fractured. The fissures were partly synsedimentary and are often lined with stromatolite-like crusts. These crusts thus far are the only known subaerial Ordovician speleothems. They reach depths of up to 30 m below the former mound top. Macroscopically the crusts form decimetre-sized, cone-shaped domal aggregates, stalactites and stalagmites. Microfabric and morphology identify them as microbially mediated speleothems in a dark environment. Combined Sr and C isotope values indicate a formation of the speleothems from meteoric waters without influence of a significant soil horizon. For the first time the age of the speleothems can be precisely constrained by delta C-13 whole-rock and brachiopod shell isotope data to the mid-Hirnantian. Repeated and/or prolonged subaerial exposure of the Boda mud mounds during the Hirnantian is evident from karst surfaces and early cements in the mound capping carbonates. The speleothems and the karst surfaces record an estimated sea-level fall in the range of 80-130 m within the time window of the Hirnantian Isotopic Carbon Excursion. This massive regression coincides with maximum ice sheet extent inferred from sections in West Gondwana. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the Geological Society
volume
172
issue
3
pages
349 - 356
publisher
The Geological Society Publishing House
external identifiers
  • wos:000353722600008
  • scopus:84928885397
ISSN
2041-479X
DOI
10.1144/jgs2014-071
language
English
LU publication?
yes
id
9ab98fa4-003c-4827-b167-753fd8b14b23 (old id 7433131)
date added to LUP
2015-06-24 08:41:43
date last changed
2017-07-02 03:04:37
@article{9ab98fa4-003c-4827-b167-753fd8b14b23,
  abstract     = {The limestones of the upper Katian Boda mud mounds (Ordovician) of the Siljan district in central Sweden are deeply fractured. The fissures were partly synsedimentary and are often lined with stromatolite-like crusts. These crusts thus far are the only known subaerial Ordovician speleothems. They reach depths of up to 30 m below the former mound top. Macroscopically the crusts form decimetre-sized, cone-shaped domal aggregates, stalactites and stalagmites. Microfabric and morphology identify them as microbially mediated speleothems in a dark environment. Combined Sr and C isotope values indicate a formation of the speleothems from meteoric waters without influence of a significant soil horizon. For the first time the age of the speleothems can be precisely constrained by delta C-13 whole-rock and brachiopod shell isotope data to the mid-Hirnantian. Repeated and/or prolonged subaerial exposure of the Boda mud mounds during the Hirnantian is evident from karst surfaces and early cements in the mound capping carbonates. The speleothems and the karst surfaces record an estimated sea-level fall in the range of 80-130 m within the time window of the Hirnantian Isotopic Carbon Excursion. This massive regression coincides with maximum ice sheet extent inferred from sections in West Gondwana.},
  author       = {Kroger, Bjorn and Ebbestad, Jan Ove R. and Lehnert, Oliver and Ullmann, Clemens V. and Korte, Christoph and Frei, Robert and Rasmussen, Christian},
  issn         = {2041-479X},
  language     = {eng},
  number       = {3},
  pages        = {349--356},
  publisher    = {The Geological Society Publishing House},
  series       = {Journal of the Geological Society},
  title        = {Subaerial speleothems and deep karst in central Sweden linked to Hirnantian glaciations},
  url          = {http://dx.doi.org/10.1144/jgs2014-071},
  volume       = {172},
  year         = {2015},
}