The δ13C chemostratigraphy of Ordovician global stage stratotypes: geochemical data from the Floian and Sandbian GSSPs in Sweden
9
Citation
29
Reference
10
Related Paper
Citation Trend
Abstract:
The δ13C chemostratigraphy of five of the seven Ordovician global stages has been published previously but no such data have been available from the Floian GSSP and most of the Sandbian GSSP in Sweden. This lack of information has now been remedied by isotope data obtained from series of closely spaced shale samples collected from the Floian stratotype at Diabasbrottet in Västergötland and the Sandbian stratotype at Fågelsång in Scania. Although the bases of these stages cannot be precisely tied to levels of conspicuous δ13C excursions, that of the Floian Stage, which is marked by the appearance of the graptolite Tetragraptus approximatus, is between the closely spaced excursions named LTNICE and BFICE. The base of the Sandbian Stage, which is defined as the appearance level of the graptolite Nemagraptus gracilis, is just below a negative excursion previously known as the "Upper Kukruse Low", which is nowadays known as the LSNICE. The relations between chemostratigraphy and graptolite and conodont biostratigraphy in the Swedish GSSPs and some coeval key sections in Baltoscandia, China, and America are briefly discussed. It is concluded that the data at hand indicate that there is good regional agreement in these relations.Keywords:
Chemostratigraphy
Conodont
Stratotype
The demarcation of the Lower—Middle Triassic boundary is a disputed problem in stratigraphic research in the world. Lower—Middle Triassic strata of different types, from platform facies to basin facies, are well developed in Southwest China. This is helpful for the research on the Global Stratotype Section and Point (GSSP). According to the research on conodonts in the Ganheqiao section in Wangmo County and the Qingyan section in Guiyang City, Guizhou Province, six conodont zones, which can be correlated with those in other regions, have been recognized. They are in ascending order as follows: ① Neospathdus cristagalli interval-zone, ② Neospathodus pakistanensis interval-zone, ③ Neospathodus waageni interval-zone, ④ Neospathodus homeri- N. triangularis assemblage-zone, ⑤ Chiosella timorensis interval-zone, ⑥ Neogongdolella regale range-zone. An evolutionary series of conodont Neospathodus—Chiosella—Neogongdolella occurred in the Ganheqiao section and Qingyan section in the Early—Middle Triassic. In this evolutionary series, a transitional Neospathodus qingyanensis appeared between Neospathodus homeri and Chiosella timorensis in the upper part of Neospathodus homeri- N. triangularis zone. This shows an excellent Early—Middle Triassic evolutionary series of conodont across the Lower—Middle Triassic boundary. The Lower—Middle Triassic boundary is located 1.5m below the top of the Ziyun Formation, where the Chiosella timorensis zone first appears on the Qingyan section; while the Lower—Middle Triassic boundary is situated 0.5 m below the top of the Ziyun Formation, where the Chiosella timorensis zone first appears on the Ganheqiao section. Based on the above-mentioned discussion, the present authors suggest that the Qingyan section can be regarded as a candidate of the GSSP of the Lower—Middle Triassic boundary and the Ganheqiao section as a reference of the GSSP of the Lower—Middle Triassic boundary for further necessary investigation.
Conodont
Stratotype
Section (typography)
Cite
Citations (15)
Conodont
Stratotype
Early Triassic
Ravine
Section (typography)
Stratigraphic unit
Cite
Citations (18)
Conodont
Radiolaria
Stratotype
Section (typography)
Cite
Citations (35)
Conodont
Section (typography)
Sequence (biology)
Cite
Citations (34)
中间的奥陶纪的底(即 Dapingian 舞台) 在 conodont Baltoniodus 的第一本外观资料(一度时髦的风尚) 被定义 ? 在 Huanghuachang， Yichang，中国，而是到要决定的另外的外形遗体的区域的边界的精确关联的 triangularis。此处，我们考察 Huanghuachang 全球标准 Stratotype 节和点(GSSP ) 节的 biostratigraphy 和 chemostratigraphy，并且在 Yichang，和 Hengtang 石场节在附近的 Chenjiahe 节上介绍我们的最近的 stratigraphic 工作， Jiangshan，浙江，它斜坡外形被认为是代表性。象 Chenjiahe 节的 chemostratigraphy 一样的 conodont 和 graptolite biostratigraphy 显示中间的奥陶纪的库也在 graptolite Azygograptus suecicus 地区以内掉落，并且在一次次要的积极的碳同位素旅行以内与高或最大的 13C 值与一致，建议基础边界能乐意地越过全部 Yangtze 峡区域被认出。综合 graptolite 和 conodont biostratigraphy 和 Hengtang 节的 chemostratigraphy， Jiangshan，显示基础边界可能在 graptolite Isograptus caduceus imitatus 以内掉落躺 Azygograptus suecicus 地区，并且与 13C 的显著落下与一致的地区。这差别显示一条多学科的途径是批评的在在哪儿的那些区域识别基础边界 Baltoniodus ? triangularis 是不在的
Conodont
Chemostratigraphy
Cite
Citations (0)
AbstractThe Stage 10 Working Group of the International Subcommission on Cambrian Stratigraphy is tasked with recommending a stratotype section and horizon for the base of Stage 10, the uppermost stage of the Cambrian System. We identify three sections in the House Range in western Utah, USA, for consideration as locations for defining and characterizing the base of the proposed stage. We also propose a boundary horizon at the base of the Eoconodontus conodont Zone combined with a distinctive negative carbon-isotope excursion named the HEllnmaria–Red Tops Boundary (HERB) event. These and other biological and nonbiological tools can be used for correlating the proposed stage.Keywords:: Cambrian Stage 10conodontstrilobitesbrachiopodscarbon isotopessequence stratigraphy AcknowledgementsRaymond Ethington and John Repetski reviewed an early version of this manuscript and made several suggestions that improved the final draft. John Cutler assisted with some of the fieldwork.
Conodont
Stratotype
Excursion
Geologic time scale
Cite
Citations (16)
Xiakou section is situated north of the central Yangtze platform with successive Late Permian to Early Triassic strata, thicker than the Global Stratotype Section and Point (GSSP) of the PermianTriassic boundary (PTB). We recognized three conodont zones across the PTB in this section by high-precision biostratigraphy. They are the Hindeodus latidentatus Clarkina meishanensis Zone, Hindeodus parvus Zone, and Isarcicella isarcica Zone in ascending order, which correspond well with the GSSP. The present biostratigraphic work on Xiakou section certainly confirmed the conodont zonation through the PTB at the GSSP and also testified to the correctness of the PTB demarcation in Xiakou section. Based on this precise demarcation of the PTB, the appearance of a clay layer, bed ZSJI266, just beneath the PTB should be an important advantage over the GSSP, because this clay layer approaches to the PTB much in contrast with those two clay layers, bed 26 and bed 28, in the GSSP. Therefore, the radiometric isotopic dating in bed ZSJI266 at Xiakou section should give a more accurate age for the PTB.
Conodont
Stratotype
Section (typography)
Cite
Citations (41)
Conodont
Laurentia
Stratotype
Chemostratigraphy
Historical geology
Orogeny
Cite
Citations (9)
Kungurian 阶段是三个留下的阶段之一二叠那被全球 Stratotype 节和点(GSSP ) 还没在底定义。在在 Urals 的 Yuryuzan' 河的候选人节产出很少 conodonts，并且在边界附近包含非海洋的沉积。为合适的、连续海洋的继任的搜索是为二叠的地层学上的分会的一项主要任务。Leonardian，直接在基础 Guadalupian Roadian 下面与它在西南美国的类型区域，并且在客观 stratigraphic 继任上演，有优先级用作一个子序列更低二叠。然而，不同方言与基于 fusuline 的 Tethyan timescale 限制 Leonardian 石块地区的关联。Conodonts 能在 Pangea 的相反的方面上在许多重要区域被相关，当与 fusuline 和 ammonoid 地区联系 conodont 地区时，然而，矛盾产生。不同分类哲学高度为冲突的原因被怀疑，而且从在韦斯特得克萨斯的类型 Roadian 有不同 conodonts。给在中亚的 Pamir 和 Darvaz 是困难的存取，在丰富的 fusulines 和 ammonoids 在整个 Tethyan 区域便于关联的地方，进一步的调查应该集中于华南，并且在哪儿与北美洲的 conodonts 许可证关联。
Conodont
Stratotype
Cite
Citations (0)