C-Isotopes and Biomarkers in Tertiary Coals

Stable carbon isotope ratios in tree rings are widely used to trace paleoenvironmental conditions, implying that cellulose of plant tissue is isotopically invariable. During previous studies at the Research Center Jülich (Germany), a cellulose extraction procedure has been established for fossil wood collected from Tertiary coals. Artificial aging experiments on wood of different taxa indicated a minor discrimination in carbon isotopic composition of cellulose relative to that obtained from untreated wood. In line with these experimental results, studies on fossil wood from German Tertiary coal deposits revealed a general isotope difference between angiosperm and gymnosperm wood specimens, as well as a higher isotopic difference between fossil wood and wood cellulose then observed in modern trees. Therefore, variations in carbon isotopic composition of fossil wood or cellulose could be used to deduce paleoenvironmental information. A continuous record of carbon isotope variations within Tertiary coal seams can be provided by analyses on coal matrix. Recently, high-frequency oscillations in carbon isotope ratios within coals of the Lower Rhine Embayment have been interpreted as a direct signal of environmental changes while medium-term variations were explained by varying proportions of gymnosperms within the peat-forming vegetation. Ongoing detailed petrographical and organic geochemical studies on Tertiary lignites of the Eastern Alpine region (FWF project P14245-CHE) revealed the importance of individual biomarkers in reconstructing the ancient biosphere. The relationships between maceral composition, organic geochemistry, palynology, and carbon isotope ratios of total organic matter and fossil wood remains provided informations on the major factors affecting the isotopic composition of coals. During the Tertiary, decreasing temperatures and atmospheric carbon dioxide levels from the Eocene to the Pliocene have been proposed. Within the frame of the proposed project coals of low rank, fossil wood and wood cellulose from the Eastern Alpine region and central Germany, covering the time interval between the Early Eocene and the Pliocene, will be investigated for its organic geochemical and stable carbon isotopic composition. It is anticipated that the combination of the results with climatic proxies from previous studies, and existing palynological data, will address fundamental questions regarding the biogeochemical carbon cycle and environmental changes.

Stable carbon isotope ratios in tree rings are widely used to trace paleoenvironmental conditions, implying that cellulose of plant tissue is isotopically invariable. During previous studies at the Research Center Jülich (Germany), a cellulose extraction procedure has been established for fossil wood collected from Tertiary coals. Artificial aging experiments on wood of different taxa indicated a minor discrimination in carbon isotopic composition of cellulose relative to that obtained from untreated wood. In line with these experimental results, studies on fossil wood from German Tertiary coal deposits revealed a general isotope difference between angiosperm and gymnosperm wood specimens, as well as a higher isotopic difference between fossil wood and wood cellulose then observed in modern trees. Therefore, variations in carbon isotopic composition of fossil wood or cellulose could be used to deduce paleoenvironmental information. A continuous record of carbon isotope variations within Tertiary coal seams can be provided by analyses on coal matrix. Recently, high-frequency oscillations in carbon isotope ratios within coals of the Lower Rhine Embayment have been interpreted as a direct signal of environmental changes while medium-term variations were explained by varying proportions of gymnosperms within the peat-forming vegetation. Ongoing detailed petrographical and organic geochemical studies on Tertiary lignites of the Eastern Alpine region (FWF project P14245-CHE) revealed the importance of individual biomarkers in reconstructing the ancient biosphere. The relationships between maceral composition, organic geochemistry, palynology, and carbon isotope ratios of total organic matter and fossil wood remains provided informations on the major factors affecting the isotopic composition of coals. During the Tertiary, decreasing temperatures and atmospheric carbon dioxide levels from the Eocene to the Pliocene have been proposed. Within the frame of the proposed project coals of low rank, fossil wood and wood cellulose from the Eastern Alpine region and central Germany, covering the time interval between the Early Eocene and the Pliocene, will be investigated for its organic geochemical and stable carbon isotopic composition. It is anticipated that the combination of the results with climatic proxies from previous studies, and existing palynological data, will address fundamental questions regarding the biogeochemical carbon cycle and environmental changes.