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A lowstand epikarstic intertidal flat from the middle Silurian of Gotland, Sweden

Calner, Mikael LU (2002) In Sedimentary Geology 148(3-4). p.389-403
Abstract
This paper describes the sedimentology, morphology and diagenesis of recently discovered Middle Silurian low-relief micro-epikarst from the Klintehamn area on western Gotland (Sweden). The epikarst represents the most distal portion of an unconformity that truncates stratigraphic units across a major part of the Baltic palaeo-basin. It formed in the intertidal area during the late stage of platform development and following a short period of regression and siliciclastic influx to the basin at the closing of the Cyrtograptus lundgreni Chron, An overlying oncolite shows signs of repeated exposure to meteoric and marine waters, supporting the interpretation of a karstic flat setting. Four microfacies with different stable isotopic signatures... (More)
This paper describes the sedimentology, morphology and diagenesis of recently discovered Middle Silurian low-relief micro-epikarst from the Klintehamn area on western Gotland (Sweden). The epikarst represents the most distal portion of an unconformity that truncates stratigraphic units across a major part of the Baltic palaeo-basin. It formed in the intertidal area during the late stage of platform development and following a short period of regression and siliciclastic influx to the basin at the closing of the Cyrtograptus lundgreni Chron, An overlying oncolite shows signs of repeated exposure to meteoric and marine waters, supporting the interpretation of a karstic flat setting. Four microfacies with different stable isotopic signatures are recognised across the unconformity: dolomitic siltstone and altered siltstone in the topmost Frojel Formation, below the contact, and ferruginous crinoid algal packstone and ferruginous oncolite grainstone above the contact, in the basal lag of the transgressive Halla Formation. Endolithic structures of inferred fungal/algal origin occur frequently in the two transgressive microfacies. The set of observations pointing towards subaerial exposure and karstic processes include: (a) an understanding of the regional geology; (b) erosional relief with undercutting and an associated conglomerate; (c) vertical and subvertical conduits (karren), indicating gravitationally controlled waters; (d) widening of fissures and subsequent polyphase fillings (splitkarren); (e) eluviated, internal sediment (e.g,, crystal silt); (f) blackening; (g) repeated etching of carbonate allochems; (h) a fitted grain-fabric; (i) circum-granular cracking; (j) pendant nonluminescent cements; (k) abundant intercrystalline and intergranular (secondary) porosity, and (1) anomalous stable isotopes. A synsedimentary iron-crust at the contact was not related to karstification but formed a few centimetres below the sediment surface during the ensuing transgression. (C) 2002 Elsevier Science B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stable isotopes, Silurian, epikarst, Gotland
in
Sedimentary Geology
volume
148
issue
3-4
pages
389 - 403
publisher
Elsevier
external identifiers
  • wos:000175528900002
  • scopus:0036258010
ISSN
0037-0738
DOI
10.1016/S0037-0738(01)00144-0
language
English
LU publication?
yes
id
8ac6648f-2f75-41c6-917c-bb3d77b35eda (old id 337743)
date added to LUP
2007-08-02 14:07:01
date last changed
2017-01-01 06:47:47
@article{8ac6648f-2f75-41c6-917c-bb3d77b35eda,
  abstract     = {This paper describes the sedimentology, morphology and diagenesis of recently discovered Middle Silurian low-relief micro-epikarst from the Klintehamn area on western Gotland (Sweden). The epikarst represents the most distal portion of an unconformity that truncates stratigraphic units across a major part of the Baltic palaeo-basin. It formed in the intertidal area during the late stage of platform development and following a short period of regression and siliciclastic influx to the basin at the closing of the Cyrtograptus lundgreni Chron, An overlying oncolite shows signs of repeated exposure to meteoric and marine waters, supporting the interpretation of a karstic flat setting. Four microfacies with different stable isotopic signatures are recognised across the unconformity: dolomitic siltstone and altered siltstone in the topmost Frojel Formation, below the contact, and ferruginous crinoid algal packstone and ferruginous oncolite grainstone above the contact, in the basal lag of the transgressive Halla Formation. Endolithic structures of inferred fungal/algal origin occur frequently in the two transgressive microfacies. The set of observations pointing towards subaerial exposure and karstic processes include: (a) an understanding of the regional geology; (b) erosional relief with undercutting and an associated conglomerate; (c) vertical and subvertical conduits (karren), indicating gravitationally controlled waters; (d) widening of fissures and subsequent polyphase fillings (splitkarren); (e) eluviated, internal sediment (e.g,, crystal silt); (f) blackening; (g) repeated etching of carbonate allochems; (h) a fitted grain-fabric; (i) circum-granular cracking; (j) pendant nonluminescent cements; (k) abundant intercrystalline and intergranular (secondary) porosity, and (1) anomalous stable isotopes. A synsedimentary iron-crust at the contact was not related to karstification but formed a few centimetres below the sediment surface during the ensuing transgression. (C) 2002 Elsevier Science B.V. All rights reserved.},
  author       = {Calner, Mikael},
  issn         = {0037-0738},
  keyword      = {stable isotopes,Silurian,epikarst,Gotland},
  language     = {eng},
  number       = {3-4},
  pages        = {389--403},
  publisher    = {Elsevier},
  series       = {Sedimentary Geology},
  title        = {A lowstand epikarstic intertidal flat from the middle Silurian of Gotland, Sweden},
  url          = {http://dx.doi.org/10.1016/S0037-0738(01)00144-0},
  volume       = {148},
  year         = {2002},
}