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Formation and significance of a middle Silurian ravinement surface on Gotland, Sweden

Eriksson, Mårten LU (2004) In Sedimentary Geology 170(3-4). p.163-175
Abstract
A laterally extensive and conspicuously smooth erosional surface is exposed near the Wenlock-Ludlow boundary on east-central Gotland, Sweden. It occurs in the reef complex area of a carbonate platform, has an undulating topography, and separates truncated bioherms and biostromes from overlying allochthonous high energy deposits. On a basin regional scale, the surface is associated to a shift from a prograding to a retrograding platform, and to a substantial hiatus in basin marginal areas (Estonia). The significance of the surface is further indicated by: (a) clear-cut truncation of the reef complex, including m-sized stromatoporoids, along a distance of at least 20 km, (b) an erosional relief exceeding 2.08 in, (c) a conspicuously smooth... (More)
A laterally extensive and conspicuously smooth erosional surface is exposed near the Wenlock-Ludlow boundary on east-central Gotland, Sweden. It occurs in the reef complex area of a carbonate platform, has an undulating topography, and separates truncated bioherms and biostromes from overlying allochthonous high energy deposits. On a basin regional scale, the surface is associated to a shift from a prograding to a retrograding platform, and to a substantial hiatus in basin marginal areas (Estonia). The significance of the surface is further indicated by: (a) clear-cut truncation of the reef complex, including m-sized stromatoporoids, along a distance of at least 20 km, (b) an erosional relief exceeding 2.08 in, (c) a conspicuously smooth nature in both palaeolows and palaeohighs, (d) present, although scarce, subaerial diagenetic indications, e.g. shallow karst features at the unconformity surface and pendant/meniscus cement in the lowermost part of overlying strata, (e) a locally occurring basal conglomeratic lag in overlying strata, and (0 peritidal indications and, as evident from at least one quarry, onlapping geometry in overlying strata. The unconformity has implications for the analysis of the middle Silurian Baltic basin evolution as well as for the interpretation of erosional surfaces on carbonate platforms in general. Based on the above characteristics, the formation of the unconformity is attributed to a relative sea-level fall, causing subaerial exposure, followed by transgressive abrasion in a rocky shore environment, The unconformity hence constitutes a ravinement surface which, based on the associated basin regional sedimentary changes, is interpreted as coinciding with a regional exposure surface (sequence boundary). It thus increases our understanding of the hitherto poorly understood palaeogeographic evolution of the middle Silurian Baltic basin. Further, the transgressive erosion was significant as well as recurrent, as indicated by the clear-cut truncation of large stromatoporoids at the unconformity surface and by truncated marine fossil fragments in upper edges of karst infills. The unconformity therefore constitutes a good example of the capability of transgressive erosion in creating stratigraphic incompleteness, and hence in removing subaerial indications, on previously exposed carbonate platforms. (C) 2004 Elsevier B.V. All rights reserved. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
Baltic basin, abrasion, ravinement surface, rocky shoreline, Gotland, Silurian
in
Sedimentary Geology
volume
170
issue
3-4
pages
163 - 175
publisher
Elsevier
external identifiers
  • wos:000224239600003
  • scopus:10044277187
ISSN
0037-0738
DOI
10.1016/j.sedgeo.2004.07.001
language
English
LU publication?
yes
id
320f6a42-8713-4a1f-8f1a-17f4b071dcf4 (old id 264439)
date added to LUP
2007-10-22 14:57:47
date last changed
2017-01-01 07:02:57
@article{320f6a42-8713-4a1f-8f1a-17f4b071dcf4,
  abstract     = {A laterally extensive and conspicuously smooth erosional surface is exposed near the Wenlock-Ludlow boundary on east-central Gotland, Sweden. It occurs in the reef complex area of a carbonate platform, has an undulating topography, and separates truncated bioherms and biostromes from overlying allochthonous high energy deposits. On a basin regional scale, the surface is associated to a shift from a prograding to a retrograding platform, and to a substantial hiatus in basin marginal areas (Estonia). The significance of the surface is further indicated by: (a) clear-cut truncation of the reef complex, including m-sized stromatoporoids, along a distance of at least 20 km, (b) an erosional relief exceeding 2.08 in, (c) a conspicuously smooth nature in both palaeolows and palaeohighs, (d) present, although scarce, subaerial diagenetic indications, e.g. shallow karst features at the unconformity surface and pendant/meniscus cement in the lowermost part of overlying strata, (e) a locally occurring basal conglomeratic lag in overlying strata, and (0 peritidal indications and, as evident from at least one quarry, onlapping geometry in overlying strata. The unconformity has implications for the analysis of the middle Silurian Baltic basin evolution as well as for the interpretation of erosional surfaces on carbonate platforms in general. Based on the above characteristics, the formation of the unconformity is attributed to a relative sea-level fall, causing subaerial exposure, followed by transgressive abrasion in a rocky shore environment, The unconformity hence constitutes a ravinement surface which, based on the associated basin regional sedimentary changes, is interpreted as coinciding with a regional exposure surface (sequence boundary). It thus increases our understanding of the hitherto poorly understood palaeogeographic evolution of the middle Silurian Baltic basin. Further, the transgressive erosion was significant as well as recurrent, as indicated by the clear-cut truncation of large stromatoporoids at the unconformity surface and by truncated marine fossil fragments in upper edges of karst infills. The unconformity therefore constitutes a good example of the capability of transgressive erosion in creating stratigraphic incompleteness, and hence in removing subaerial indications, on previously exposed carbonate platforms. (C) 2004 Elsevier B.V. All rights reserved.},
  author       = {Eriksson, Mårten},
  issn         = {0037-0738},
  keyword      = {Baltic basin,abrasion,ravinement surface,rocky shoreline,Gotland,Silurian},
  language     = {eng},
  number       = {3-4},
  pages        = {163--175},
  publisher    = {Elsevier},
  series       = {Sedimentary Geology},
  title        = {Formation and significance of a middle Silurian ravinement surface on Gotland, Sweden},
  url          = {http://dx.doi.org/10.1016/j.sedgeo.2004.07.001},
  volume       = {170},
  year         = {2004},
}