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Late Ordovician-Early Silurian delta C-13 chemostratigraphy in the Upper Mississippi Valley: implications for chronostratigraphy and depositional interpretations

Bergstrom, Stig M.; Kleffner, Mark and Schmitz, Birger LU (2011) In Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102. p.159-178
Abstract
A pioneer study of the previously unknown delta C-13 chemostratigraphy in the Ordovician/Silurian boundary interval in eastern Iowa and northeastern Illinois resulted in the discovery of the Hirnantian Isotope Carbon Excursion (HICE). The presence of this major isotope excursion in the Mosalem Formation in Iowa and the Wilhelmi Formation in Illinois, which indicates that the excursion interval in these units is of Hirnantian (latest Ordovician) rather than Early Silurian age, necessitates a revised chronostratigraphic classification of these units. Although the precise level of the Ordovician/Silurian boundary remains somewhat uncertain in the absence of the diagnostic graptolites, it is herein placed in the upper part, but well below the... (More)
A pioneer study of the previously unknown delta C-13 chemostratigraphy in the Ordovician/Silurian boundary interval in eastern Iowa and northeastern Illinois resulted in the discovery of the Hirnantian Isotope Carbon Excursion (HICE). The presence of this major isotope excursion in the Mosalem Formation in Iowa and the Wilhelmi Formation in Illinois, which indicates that the excursion interval in these units is of Hirnantian (latest Ordovician) rather than Early Silurian age, necessitates a revised chronostratigraphic classification of these units. Although the precise level of the Ordovician/Silurian boundary remains somewhat uncertain in the absence of the diagnostic graptolites, it is herein placed in the upper part, but well below the top, of the Mosalem Formation and at the top of the Wilhelmi Formation. During a major regression following the deposition of the Maquoketa Shale, the upper part of the latter elastic unit was in some places deeply eroded, resulting in a topographically dissected landscape with upland areas separated by wide incised valleys. During a subsequent late Hirnantian transgression, these palaeovalleys were gradually filled with marine sediments, but the upland areas were not transgressed until earliest Silurian times. The new chemostratigraphical evidence is in good agreement with the available biostratigraphical data, especially from corals, conodonts, and brachiopods. A preliminary chemostratigraphical study of the presumably coeval Edgewood Group successions in Pike County, northeastern Missouri failed to document any heavy delta C-13 values characteristic of the HICE and some, or all, of the Hirnantian values obtained there may be diagenetically overprinted. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
conodonts, depositional history, eustacy, geological evolution, HICE, Hirnantian, Upper Ordovician
in
Earth and Environmental Science Transactions of the Royal Society of Edinburgh
volume
102
pages
159 - 178
publisher
Royal Society of Edinburgh
external identifiers
  • wos:000307605400002
  • scopus:84865273524
ISSN
1755-6929
DOI
10.1017/S1755691012011061
language
English
LU publication?
yes
id
a83d905a-f0ba-47ba-ab2b-85e21d8f0d8e (old id 3470425)
date added to LUP
2013-02-25 08:05:57
date last changed
2017-08-27 03:07:45
@article{a83d905a-f0ba-47ba-ab2b-85e21d8f0d8e,
  abstract     = {A pioneer study of the previously unknown delta C-13 chemostratigraphy in the Ordovician/Silurian boundary interval in eastern Iowa and northeastern Illinois resulted in the discovery of the Hirnantian Isotope Carbon Excursion (HICE). The presence of this major isotope excursion in the Mosalem Formation in Iowa and the Wilhelmi Formation in Illinois, which indicates that the excursion interval in these units is of Hirnantian (latest Ordovician) rather than Early Silurian age, necessitates a revised chronostratigraphic classification of these units. Although the precise level of the Ordovician/Silurian boundary remains somewhat uncertain in the absence of the diagnostic graptolites, it is herein placed in the upper part, but well below the top, of the Mosalem Formation and at the top of the Wilhelmi Formation. During a major regression following the deposition of the Maquoketa Shale, the upper part of the latter elastic unit was in some places deeply eroded, resulting in a topographically dissected landscape with upland areas separated by wide incised valleys. During a subsequent late Hirnantian transgression, these palaeovalleys were gradually filled with marine sediments, but the upland areas were not transgressed until earliest Silurian times. The new chemostratigraphical evidence is in good agreement with the available biostratigraphical data, especially from corals, conodonts, and brachiopods. A preliminary chemostratigraphical study of the presumably coeval Edgewood Group successions in Pike County, northeastern Missouri failed to document any heavy delta C-13 values characteristic of the HICE and some, or all, of the Hirnantian values obtained there may be diagenetically overprinted.},
  author       = {Bergstrom, Stig M. and Kleffner, Mark and Schmitz, Birger},
  issn         = {1755-6929},
  keyword      = {conodonts,depositional history,eustacy,geological evolution,HICE,Hirnantian,Upper Ordovician},
  language     = {eng},
  pages        = {159--178},
  publisher    = {Royal Society of Edinburgh},
  series       = {Earth and Environmental Science Transactions of the Royal Society of Edinburgh},
  title        = {Late Ordovician-Early Silurian delta C-13 chemostratigraphy in the Upper Mississippi Valley: implications for chronostratigraphy and depositional interpretations},
  url          = {http://dx.doi.org/10.1017/S1755691012011061},
  volume       = {102},
  year         = {2011},
}