Abstract
Research subject. Changes in the trophic structure of shallow-water pelagic ecosystems at the Devonian/Carboniferous border were investigated by studying the carbon isotope composition of conodont organic matter.Materials and methods. Two Devonian-Carboniferous shallow-water clayey-carbonate sections located in the southern part of the Pechora-Kozhva Uplift (Pechora Plate) were analysed. The Devonian-Carboniferous boundary was detected by the first occurrences of Siphonodella sulcata, S. semichatovae and Patrognathus crassus, as well as by the last occurrence of Pseudopolygnathus graulichi. The carbon isotope composition was investigated both in whole-rock carbonate samples and the conodont organic matter of two dominant species (Polygnathus parapetus and P. communis communis).Results. The distribution of stable carbon isotopes in the organic matter of conodont elements accompanied by the data on carbonate isotope composition allowed us to suggest changes in the food composition of the dominant taxa during the Late Famennian-Early Tournaisian transition. It was assumed that the latest Famennian representatives of Polygnathus parapetus and P. communis communis consumed largely phyto- and zooplankton, which is characterized by a light isotopic composition of organic carbon. The nutrition based on phyto- and zooplankton with a heavier isotopic composition of organic carbon was suggested for the early Tournaisian representatives of these species.Conclusions. The discovered variations in the carbon isotope composition of conodont organic matter in shallow-water facies may correspond to the change from the eutrophic pelagic ecosystem to the oligotrophic ecosystem, and/or global perturbation of the carbon cycle due to climatic changes. Since the available data is limited to two geological sections, it is impossible to unambiguously interpret the scale (local, regional, global) of these variations and their correlation potential.
Highlights
Уровень границы девонской и каменноугольной систем установлен по первым находкам конодонтов Siphonodella sulcata, S. semichatovae, Patrognathus crassus и исчезновению Pseudopolygnathus graulichi
Преобладание питания фито- и зоопланктоном, содержащим органический углерод с легким изотопным составом, предполагается для позднефаменских представителей Polygnathus parapetus и P. communis communis
Changes in the trophic structure of shallow-water pelagic ecosystems at the Devonian/Carboniferous border were investigated by studying the carbon isotope composition of conodont organic matter
Summary
Положительные сдвиги в изотопном соотношении карбонатного углерода в зоне praesulcata верхнего фамена и в нижней части зоны sulcata нижнего турне фиксируются в различных бассейнах в качестве изотопных событий HICE и P1 (Qie et al, 2016). Их возникновение связывают с глобальными изменениями в углеродном цикле, в частности с глобальным повышением первичной биопродуктивности и увеличением объемов захоронения органического вещества. Их соотношение с биостратиграфическими данными в изученных разрезах, совпадающее с таковым в других регионах, повышает достоверность используемого в данной работе стратиграфического расчленения. Низкие амплитуды наблюдаемых в изученных разрезах отклонений изотопного состава карбонатного углерода характерны для мелководных бассейнов. Изотопные сдвиги сходной амплитуды в пограничном девонско-каменноугольном интервале отмечены, например, во многих мелководных последовательностях по всему миру (Buggisch et al, 2008). Изотопный состав углерода органического вещества конодонтовых элементов в разрезах на р. 121-1/16 121-2/16 121-4/16 121-4/16 121-4/16 121-7/16 121-7/16 121-9/16 121-10/16 121-11/16 121-14/16 121-17/16 121-17/16 121-1/96 121-1/96 121-1/18 121-1/18 121-1/18 121-1/18 121-1/18 121-19/16 121-19/16 121-1-8/90 121-14/96 121-1-10/90 101-5/19 111A-2/19 111A-3/19 111A-1/19 111A-2/19 111A-4/19 111A-5/19 111A-6/19
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
