Carbon isotope composition and its implications of Lower Cretaceous Aptian-Albian shallow water carbonates in the Cuoqin Basin, North Tibet

2004 ◽  
Vol 47 (3) ◽  
pp. 247 ◽  
Author(s):  
Jingquan ZHU
Keyword(s):  
Shallow Water ◽  
Carbon Isotope ◽  
Lower Cretaceous ◽  
Isotope Composition ◽  
Carbon Isotope Composition

scholarly journals Preliminary results of studying the carbon isotope composition of conodont elements at the border of Devonian and Carboniferous periods (Kamenka river sections, Pechora carbonate platform)

LITOSFERA ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 829-841
Author(s):  
A. V. Zhuravlev ◽  
I. V. Smoleva
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Isotopic Composition ◽  
Shallow Water ◽  
Carbon Isotope ◽  
Stable Carbon Isotopes ◽  
Carbonate Platform ◽  
Isotope Composition ◽  
Carbon Isotope Composition ◽  
Oligotrophic Ecosystem

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.

The Homerian (late Wenlock, Silurian) carbon isotope excursion from Perunica: Does dolomite control the magnitude of the carbon isotope excursion?

2016 ◽  
Vol 53 (7) ◽  
pp. 695-701 ◽  
Author(s):  
Jiří Frýda ◽  
Barbora Frýdová
Keyword(s):  
Shallow Water ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Carbon Isotope Composition ◽  
The Other ◽  
Fluid Composition ◽  
Carbon Isotope Excursion ◽  
O Isotope ◽  
Different Content ◽  
Carbonate Composition

The δ13Ccarb records from two geographically close sections of the shallow-water Kozel Limestone Member (late Wenlock Motol Formation; Perunica microplate) significantly differ in the magnitude of the Homerian carbon isotope excursion as well as in their dolomite content. The present paper tests a hypothesis as to whether a difference of about 2‰ in the magnitude of the δ13Ccarb anomaly is caused by the different content of dolomite, which could be enriched in both 13C and 18O relative to coexisting calcite, as has been suggested by experimental data. The new data obtained reveal that the δ18O composition of calcite and dolomite was probably controlled by the pore-fluid composition during limestone diagenesis and that both carbonates seem to be close to equilibrium in oxygen isotope composition. On the other hand, the δ13C values of dolomite are similar to those of calcite, and thus the carbon isotope composition of both carbonates was probably determined by the precursor carbonate composition. Moreover, the values of δ13Cdolomite/δ13Ccalcite ratios as well as their variability suggest that both calcite and dolomite did not reach equilibrium in their carbon isotope composition. Whole-rock, mineralogical, and C and O isotope data clearly show that dolomite is not the cause for the differences in magnitudes of the δ13C records observed between dolomite-bearing and dolomite-lacking shallow-water limestone successions. The question as to whether the observed differences in the δ13C records of the studied sections across the Homerian carbon isotope excursion were controlled by the dependence of seawater composition on water depth and (or) proximity to shoreline or if the δ13C values were later affected by secondary processes during limestone diagenesis is still unsolved.

The influence of hydrodynamics on the carbon isotope composition of inorganically precipitated calcite

2021 ◽  
Vol 565 ◽  
pp. 116932
Author(s):  
Hao Yan ◽  
Wolfgang Dreybrodt ◽  
Huiming Bao ◽  
Yongbo Peng ◽  
Yu Wei ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Isotope Composition ◽  
Carbon Isotope Composition
Sign in / Sign up

Export Citation Format

Share Document