| 1. |
- Bergstroem, Stig M., et al.
(author)
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A new upper Middle Ordovician-Lower Silurian drillcore standard succession from Borenshult in Ostergotland, southern Sweden: 2. Significance of delta C-13 chemostratigraphy
- 2012
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In: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 134:1, s. 39-63
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Journal article (peer-reviewed)abstract
- A total of 239 isotope samples are used for establishing the delta C-13 chemostratigraphy in the upper Middle Ordovician to Lower Silurian succession in the approximately 70 m long Borenshult drillcore. The study interval starts in the upper Darriwilian Furudal Limestone and ends in the Rhuddanian Motala Formation. Four named delta C-13 excursions are recognized in 3-4 formations, namely the Guttenberg isotope carbon excursion (GICE) in the lower-middle Freberga Formation, the Kope (Rakvere) excursion in the uppermost Freberga Formation and possibly the Slandrom Formation, the Whitewater (Moe) excursion in the Lower Member of the Jonstorp Formation and the Hirnantian isotope carbon excursion (HICE) in the Loka Formation. The Middle Darriwilian isotope carbon excursion (MDICE) is missing in the drillcore and it is suggested that the study succession starts just above the interval of this excursion, which is in agreement with the range of MDICE in other Baltoscandic successions. The widespread Waynesville (Saunja) excursion may be cut out by the prominent unconformity below the Fjacka Shale. The two most conspicuous excursions are the GICE (peak value similar to+1.9 parts per thousand) and the HICE (peak value similar to+3.7 parts per thousand), whereas the other excursions are represented by relatively minor perturbations in the delta C-13 curve. The Borenshult drillcore chemostratigraphy, which has been closely tied to conodont biostratigraphy, is quite similar to that of Estonian drillcores and is useful for not only trans-Baltic but also trans-Atlantic correlations. It is the first drillcore-based delta C-13 chemostratigraphy from the Swedish Ordovician.
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| 2. |
- Bergstroem, Stig M., et al.
(author)
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First record of the Hirnantian (Upper Ordovician) delta C-13 excursion in the North American Midcontinent and its regional implications
- 2006
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In: Geological Magazine. - 0016-7568. ; 143:5, s. 657-678
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Research review (peer-reviewed)abstract
- The most prominent of the two major global delta C-13 excursions in the Ordovician, the Hirnantian delta C-13 excursion (HICE), which is previously recorded from the uppermost Ordovician in a few sections in Nevada, Quebec, Arctic Canada, Baltoscandia, Scotland and China, is documented for the first time from the North American Midcontinent. Samples through the Girardeau Limestone and Leemon Formation in Missouri and Illinois show elevated delta C-13 values of + 4 parts per thousand to + 5 parts per thousand. Although not determined precisely, the beginning of the HICE is likely to be in the upper part of the Orchard Creek Shale, and it ends in the upper Leemon Formation. Being extraordinarily useful chronostratigraphically, the presence of the HICE makes it possible to provide a firm dating of the study interval, whose age has long been controversial. Comparison between the study sections and coeval HICE sequences in North America and Europe show striking similarities, especially in sea-level history, indicating that major local lowstands reflect eustatic sea-level changes. A comparison with Hirnantian diamictite successions in North and South Africa and Argentina suggests that these lowstands correspond to two major Gondwanan glacial episodes.
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| 3. |
- Albanesi, Guillermo L., et al.
(author)
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Darriwilian (Middle Ordovician) delta C-13(carb) chemostratigraphy in the Precordillera of Argentina: Documentation of the middle Darriwilian Isotope Carbon Excursion (MDICE) and its use for intercontinental correlation
- 2013
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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 389, s. 48-63
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Journal article (peer-reviewed)abstract
- Although documented from Estonia, Latvia, Sweden, eastern North America, and China, the Middle Ordovician (Darriwilian) positive delta C-13 excursion known as the MDICE has previously not been recognized with certainty in South America. The most promising region in South America for detailed Middle Ordovician carbon isotope research is the Precordillera of western Argentina, where there are many excellent exposures of biostratigraphically well-dated carbonate successions spaning the Tremadocian through Sandbian stratigraphic interval. For this project, we collected numerous isotope and conodont samples from the middle Darriwilian Las Chacritas and Aguaditas formations at their type localities, which yielded important biostratigraphic data as well as informative delta C-13(carb) values. In the E. pseudoplanus Zone in the upper half of the Las Chacritas Formation, there is a relatively modest but distinct delta C-13(carb) excursion. Because its stratigraphic position and magnitude closely agree with the MDICE in other parts of the world, we recognize it as the first firm record of this excursion in South America. The fact that the delta C-13(carb) curve from the Las Aguaditas Formation shows no such excursion is due to the existence of a stratigraphic gap between the Lower and Middle Members of this formation that cuts out the excursion interval. The Precordilleran MDICE is used for detailed long-range correlations with successions in Baltoscandia, Newfoundland, and China illustrating the usefulness of also this delta C-13(carb) excursion as a global stratigraphic tool. A recent proposal of a greatly extended chronostratigraphic range of the Table Head Group on Newfoundland is rejected based on well-established biostratigraphic evidence. (C) 2013 Elsevier B.V. All rights reserved.
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| 4. |
- Bergstroem, Stig M., et al.
(author)
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A new upper Middle Ordovician-Lower Silurian drillcore standard succession from Borenshult in Ostergotland, southern Sweden: 1. Stratigraphical review with regional comparisons
- 2011
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In: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 133:3-4, s. 149-171
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Journal article (peer-reviewed)abstract
- A recent drilling at Borenshult near Motala resulted in discovery of the stratigraphically most complete succession through the upper Darriwilian-Rhuddanian interval known in Ostergotland. The approximately 70m long drillcore succession is subdivided into eight formations, the oldest being the late Darriwilian Furudal Limestone and the youngest being the Rhuddanian Motala Formation. Conodonts are used for a detailed biostratigraphic classification of the Borenshult drillcore into three subzones of the Pygodus serra Zone, two subzones of the Pygodus anserinus Zone, and three subzones of the Amorphognathus tvaerensis Zone. The base of the Amorphognathus superbus Zone is taken to be similar to 10m above the Kinnekulle K-bentonite, that of the Amorphognathus ordovicicus just below the Fjacka Shale, and that of the Ozarkodina hassi Zone at the base of the Middle Member of the Loka Formation. Because of its unique lithology and paleontology and its wide geographic occurrence, this member is formally named herein the Skultorp Member. The previously uncertain stratigraphical position of the internationally known "Borenshult fauna" is shown to correlate with the Skultorp Member. A regional comparison of the Borenshult drillcore succession shows it to be most similar to coeval successions in Vastergotland and Dalarna but there are some significant regional differences. The average rate of net rock accumulation during late Darriwilian and Sandbian time is calculated to be similar to 3-4 mm/ka.
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| 5. |
- Bergstroem, Stig M., et al.
(author)
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First documentation of the Ordovician Guttenberg delta C-13 excursion (GICE) in Asia: chemostratigraphy of the Pagoda and Yanwashan formations in southeastern China
- 2009
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In: Geological Magazine. - 0016-7568. ; 146:1, s. 1-11
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Journal article (peer-reviewed)abstract
- The only published VC data from the Ordovician of China are from the Lower and Upper Ordovician, and only the latter records include a significant excursion, namely the Hirnantian excursion (HICE). Our recent chemostratigraphic work on the Upper Ordovician (Sandbian-Katian) Pagoda and Yanwashan formations at several localities oil the Yangtze Platform and Chiangnan (Jiangnan) slope belt has resulted in the recognition of a positive delta C-13 excursion that has values of similar to+1.5 parts per thousand above baseline values. This excursion starts a few metres above a stratigraphic interval with B. alobatus Subzone conodonts as well as graptolites of the N. gracilis Zone. The distinctive conodonts Amorphognathus aff. Am. ventilatus and Hamarodus europaeus first occur at, or very near, the excursion interval. Because these conodonts appear in the stratigraphic interval of the Guttenberg VC excursion (GICE) in Estonia, we identify the Chinese excursion as the GICE. This is the first record of the GICE in the entire Asian continent. It confirms that GICE is a global excursion and provides an illustration of how VC chemostratigraphy, combined with new biostratigraphic data, solves the problem of the previously controversial age of the Pagoda Formation and how this classical stratigraphic unit correlates with the Baltoscandian and North American successions.
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| 6. |
- Bergstroem, Stig M., et al.
(author)
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Global Upper Ordovician correlation by means of delta C-13 chemostratigraphy: implications of the discovery of the Guttenberg delta C-13 excursion (GICE) in Malaysia
- 2010
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In: Geological Magazine. - 0016-7568. ; 147:5, s. 641-651
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Journal article (peer-reviewed)abstract
- Apart from a single study of the early Katian delta C-13 chemostratigraphy in two regions in China, no investigations of the Sandbian and Katian chemostratigraphy have been published from anywhere in Asia. A recent study of the conodont biostratigraphy of the classical Ordovician succession on Langkawi Islands, peninsular Malaysia, showed the presence there of strata coeval with those having the Guttenberg Carbon Excursion (GICE) on the Yangtze Platform. In an effort to establish for the first time the presence of this widespread delta C-13 excursion in southern Asia, a series of samples from the upper part of the Kaki Bukit Formation was isotopically analysed. This resulted in the discovery of a conspicuous delta C-13 excursion with peak values of similar to 2% above the baseline values. The excursion is located just above the Baltoniodus alobatus Subzone and near the level of the first appearance of Hamarodus europaeus, hence the same stratigraphic position as the GICE on the Yangtze Platform. Using the GICE, the Malaysian study interval is closely correlated with the GICE intervals at three localities representing an approximately 23 000 km long transect from Malaysia across Baltoscandia to central North America. This shows the usefulness of delta C-13 chemostratigraphy to clarify previously obscure stratigraphic relationships between geographically very widely separated localities.
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| 7. |
- Bergstroem, Stig M., et al.
(author)
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Hirnantian (latest Ordovician) delta C-13 chemostratigraphy in southern Sweden and globally: a refined integration with the graptolite and conodont zone successions
- 2014
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In: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:2, s. 355-386
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Journal article (peer-reviewed)abstract
- The delta C-13(org) chemostratigraphy of the Hirnantian and lower Rhuddanian in the biostratigraphically well-controlled Rostanga-1 drillcore from west-central Scania is used for an improved integration of the Hirnantian Isotope Carbon Excursion (HICE) with the standard graptolite zonation. In this drillcore succession, the end of the HICE corresponds to the top of the range of Metabolograptus persculptus. Baseline delta C-13(org) values occur in the uppermost Hirnantian Avitograptus avitus Faunal Interval as well as in the Rhuddanian Akidograptus ascensus Zone, and the isotope curve is also tied to the Swedish uppermost Katian and Hirnantian trilobite zonation. Chemostratigraphic data from sections in Vastergotland confirm that the beginning of the HICE is at, or very close to, the base of the Skultorp Member of the Loka Formation. The biostratigraphically less precisely controlled end of the HICE is at least locally in the Upper Member of the same formation. The graptolite biostratigraphy in the Mt. Kinnekulle succession indicates that the lowermost Kallholn Formation, which has long been known as the Leonaspis (formerly Acidaspis) Shale, is of Hirnantian rather than earliest Silurian age which is consistent with the age of the lowermost Kallholn Formation in the Rostanga-1 drillcore. Comparisons with Hirnantian sections in the United Kingdom, North America and China make it possible to improve the calibration of the HICE with conodont and graptolite biostratigraphy and confirm the usefulness of delta C-13(org) chemostratigraphy for detailed correlations. The upper Katian carbon chemostratigraphy in key sections in North America and eastern Baltoscandia indicates that the Elkhorn and Paroveja excursions are the same. Available data are used for a new Hirnantian eustasy-climate-faunal evolution model.
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| 8. |
- Bergstroem, Stig M., et al.
(author)
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Lower Katian (Upper Ordovician) delta(13)C chemostratigraphy, global correlation and sea-level changes in Baltoscandia
- 2011
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In: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 133:1-2, s. 31-47
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Journal article (peer-reviewed)abstract
- A long-standing problem in the Ordovician stratigraphy of south-eastern Norway has been to the relations between the Mjosa Formation in the Lake Mjosa region and coeval strata in the Oslo region. The recent discovery of the globally distributed Guttenberg delta(13)C excursion (Guttenberg Isotopic Carbon Excursion) in the Mjosa region provided the impetus to search for this excellent chemostratigraphic marker in the classical Oslo region succession, where it was found in the Frognerkilen Formation. Another positive delta(13)C excursion, which we identify as the Kope excursion, was discovered in the Solvang Formation. The new data show that the lower Katian delta(13)C chemostratigraphy in the Oslo region is closely similar to that from south-eastern and southern Estonia. This permits detailed correlations across Baltoscandia, which are useful for recognising the Baltic stage boundaries in the Oslo region succession. Both the Lake Mjosa and Oslo regions study successions can be chemostratigraphically correlated with those in North America and eastern Asia. The newly established stratigraphic relations in the Oslo region are also used for a re-assessment of lower Katian local and eustatic sea-level changes.
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| 9. |
- Bergstroem, Stig M., et al.
(author)
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The delta C-13 chemostratigraphy of the Upper Ordovician Mjosa Formation at Furuberget near Hamar, southeastern Norway: Baltic, Trans-Atlantic, and Chinese relations
- 2010
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In: Norsk Geologisk Tidsskrift. - 1502-5322. ; 90:1-2, s. 65-78
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Journal article (peer-reviewed)abstract
- Whereas no studies have previously been carried out on the delta C-13 chemostratigraphy of the Sandbian-Katian (Upper Ordovician) succession anywhere in Norway, such investigations in Sweden and the East Baltic region have made the delta C-13 chemostratigraphy of that interval well known. 1 an attempt to document for the first time the presence of the globally distributed and stratigraphically important Guttenberg Carbon Isotope Excursion (GICE), 45 samples were collected at 2 m intervals through the Furnesfjorden and Galas members of the Mjosa Formation from two sections at Furuberget in the Nes-Hamar District 70 km north of the City of Oslo. Relatively high delta C-13 values, which are interpreted to represent the GICE, were obtained throughout the Galls Member. The presence of this delta C-13 excursion in the middle part of the Mjosa Formation, combined with biostratigraphic and other evidence, are used for detailed correlations of the Mjosa Formation with other successions in Baltoscandia, North America, and on the Yangtze Platform in southern China.
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