| 1. |
- Calner, Mikael, et al.
(författare)
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d(13)C chemostratigraphy in the Lower-Middle Ordovician succession of Oland (Sweden) and the global significance of the MDICE
- 2014
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:1, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- Based on the Tingskullen drillcore, we present the first continuous carbon isotope stratigraphy from the Lower-Middle Ordovician orthoceratite limestone of oland, Sweden. The extremely condensed Tremadocian and Floian stages include large gaps as well as the Ceratopyge Regressive Event and the widespread Evae transgression accompanied by prominent shifts in the C-13 record. The Dapingian and Darriwilian stages are characterised by low sedimentation rates and a relatively complete sedimentary record. A total of 99 whole-rock samples were analysed for carbon isotope geochemistry from the Ordovician part of the succession (46m thick). The most striking anomaly detected is the middle Darriwilian isotope carbon excursion (MDICE) that appears unusually well developed and complete for the region, and thus forms an important proxy for intercontinental correlation of the succession.
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| 2. |
- del Rey, Álvaro, et al.
(författare)
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Stable ocean redox during the main phase of the Great Ordovician Biodiversification Event
- 2022
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Ingår i: Communications Earth and Environment. - : Springer Science and Business Media LLC. - 2662-4435. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- The Great Ordovician Biodiversification Event (GOBE) represents the greatest increase in marine animal biodiversity ever recorded. What caused this transformation is heavily debated. One hypothesis states that rising atmospheric oxygen levels drove the biodiversification based on the premise that animals require oxygen for their metabolism. Here, we present uranium isotope data from a Middle Ordovician marine carbonate succession that shows the steepest rise in generic richness occurred with global marine redox stability. Ocean oxygenation ensued later and could not have driven the biodiversification. Stable marine anoxic zones prevailed during the maximum increase in biodiversity (Dapingian–early Darriwilian) when the life expectancy of evolving genera greatly increased. Subsequently, unstable ocean redox conditions occurred together with a marine carbon cycle disturbance and a decrease in relative diversification rates. Therefore, we propose that oceanic redox stability was a factor in facilitating the establishment of more resilient ecosystems allowing marine animal life to radiate.
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| 3. |
- Lehnert, Oliver, et al.
(författare)
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delta C-13 chemostratigraphy in the upper Tremadocian through lower Katian (Ordovician) carbonate succession of the Siljan district, central Sweden
- 2014
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Ingår i: Estonian Journal of Earth Sciences. - : Estonian Academy Publishers. - 1736-7557 .- 1736-4728. ; 63:4, s. 277-286
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Tidskriftsartikel (refereegranskat)abstract
- Based on delta C-13 data from two drillcores recovered from the Siljan district, we present a first continuous carbon isotope record of the upper Tremadocian-lower Katian limestone succession of central Sweden. New names for some isotopic carbon excursions from the Cambrian-Ordovician boundary through the basal Darriwilian are introduced. The Mora 001 core from the western part of the Siljan impact structure ranges through the Lower-Middle Ordovician, whereas the Solberga 1 core from its eastern part ranges through the Middle-lower Upper Ordovician. Upper Tremadocian and Floian units are extremely condensed and include extensive stratigraphic gaps. Multiple hardgrounds, sometimes with minor karstic overprint, imply recurrent periods of erosion and/or non-deposition. Like in other parts of Sweden, the Dapingian and Darriwilian succession is characterized by a relatively complete sedimentary record and low sedimentation rates.
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| 4. |
- Wu, Rongchang, et al.
(författare)
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Early-Middle Ordovician conodont biofacies on the Yangtze Platform margin, South China: Applications to palaeoenvironment and sea-level changes
- 2014
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120. ; 96, s. 194-204
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Tidskriftsartikel (refereegranskat)abstract
- 9172 Conodonts have been recovered from the uppermost Hunghuayuan Formation and the Zitai Formation at two sections in Shitai County, southern Anhui Province, South China, which was situated close to the margin of the Lower Yangtze Platform during the Early to Middle Ordovician. Systematic and multivariate statistical studies on these conodonts permit recognition of seven conodont biofacies: Tropodus biofacies, Diaphorodus biofacies, Oepikodus biofacies, Baltoniodus biofacies, Paroistodus biofacies, Periodon biofacies and Protopanderodus biofacies. Each biofacies is restricted to a particular lithofacies and stratal position and shows a consistent order and/or position within the succession. Turnover of these conodont biofacies is related to sea-level changes. The transgressive-regressive patterns demonstrated by the conodont biofacies compare closely to published sea level curves for South China, and highlight the utility of conodont biofacies as a means of confirming sedimentological evidence of relative sea-level change. (C) 2014 Elsevier Ltd. All rights reserved.
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| 5. |
- WU, RONGCHANG, et al.
(författare)
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Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE
- 2017
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Ingår i: Geological Magazine. - 0016-7568. ; 154:02, s. 334-353
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Tidskriftsartikel (refereegranskat)abstract
- One of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) is herein documented from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (~46 m) on the island of Öland, southeastern Sweden, we provide an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including the Oepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus (Microzarkodina hagetiana and Microzarkodina ozarkodella subzones), E. suecicus, Pygodus serra (E. foliaceus, E. reclinatus, E. robustus and E. lindstroemi subzones) and Pygodus anserinus zones in ascending order. The δ13Ccarb record reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness of c. 27 m in the core and spans the Eoplacognathus pseudoplanus, E. suecicus, Pygodus serra and P. anserinus conodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China.
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| 6. |
- Wu, Rongchang, et al.
(författare)
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Lower-Middle Ordovician delta C-13 chemostratigraphy of western Baltica (Jamtland, Sweden)
- 2015
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Ingår i: Palaeoworld. - : Elsevier BV. - 1875-5887 .- 1871-174X. ; 24:1-2, s. 110-122
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Tidskriftsartikel (refereegranskat)abstract
- The province of Jamtland, central Sweden, records a well-preserved but very thin suite of the Lower-Middle Ordovician cool-water carbonates. In this study we present the first carbon isotope profile for these strata on the basis of whole-rock samples from the Brunflo 2 core. The studied succession is 41.55 m thick and includes, in ascending order, the Bjorkasholmen Formation, Latorp Limestone, Toyen Shale, and the Lanna, Holen, and Segerstad limestones. We identify two distinct positive delta C-13 excursions that can be used for intra-as well as inter-continental correlations. A positive excursion in the Toyen Shale probably correlates to the mid-late Floian and the Oepikodus evae Zone in Baltica and Precordillera, and the Reutterodus andinus Zone in North America. A continuous increase in delta C-13 values through the upper Holen Limestone and the preserved part of the overlying Segerstad Limestone is interpreted as the rising limb of the Middle Darriwilian Isotope Carbon Excursion (MDICE), an important tie-point for the global correlation of the Jamtland strata. Negative delta C-13 values associated with the Latorp Limestone may correlate with similar low values in the late Tremadocian and early Floian of the Argentine Precordillera and the Shingle Pass and Ibex sections in North America. (C) 2015 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.
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| 7. |
- Yan, Guanzhou, et al.
(författare)
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The record of early Silurian climate changes from South China and Baltica based on integrated conodont biostratigraphy and isotope chemostratigraphy
- 2022
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 606
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Tidskriftsartikel (refereegranskat)abstract
- New conodont and stable isotope data are presented from the classical Baizitian section in the Yanbian County of Sichuan Province, South China. The Telychian to Sheinwoodian strata were sampled and studied for carbon isotope stratigraphy and conodont biostratigraphy. The paired δ13Ccarb and δ13Corg data reveal a pronounced positive excursion, the Manitowoc carbon isotope excursion (Manitowoc CIE, ‘Manitowoc Excursion’) spanning the upper Pterospathodus eopennatus Zone and the lower Pterospathodus amorphognathoides amorphognathoides Superzone, with an increase of ca. 2‰ in δ13Ccarb and ca. 5‰ in δ13Corg. Well-bracketed by conodont biostratigraphy, the Manitowoc CIE is an essential tie-point for correlation between the Baizitian succession and the Telychian strata of Baltica and Laurentia. Our new δ13Ccarb and δ13Corg data imply that the carbon isotope excursion previously recognized as the ‘Ireviken Excursion’ (Early Sheinwoodian Carbon Isotope Excursion) at Baizitian should be revised as being the Manitowoc CIE. The Δ13C data presented in this study further suggest a slight concurrent drop of atmospheric CO2, and thus add evidence for a perturbation of the global carbon cycle during the middle Telychian. Based on the combined information from the conodont apatite oxygen isotope records from Estonia and the significant stratigraphic gaps recognized at the Baizitian section, we propose that the latter stratigraphic gaps should correlate with the Telychian Valgu and the early Sheinwoodian glaciation.
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