Biomarker and carbon isotope variation in coal and fossil wood of Central Europe through the Cenozoic

Carbon isotope analyses of terrigenous organic matter are often used to reconstruct changes in the isotopic composition of upper ocean and atmospheric carbon reservoirs. Carbon isotope values from tree-rings, fossil wood, and coal matrices have been related to climatic change (e.g. temperature, humidity) via water-use efficiency of land plants. In this study, we report on carbon isotope analyses on low-rank coal deposits of the Alpine Realm and Middle German Lignite District covering the Early Eocene to Pliocene time interval.Fossil wood and extracted wood cellulose from gymnosperms and angiosperms, respectively, are used for paleoenvironmental reconstructions. The trend in δ13C is parallel to the carbon isotope record obtained from benthic foraminifera, because both data sets sample a common reservoir in the atmosphere.The evaluation of the magnitudes of δ13C variations of coal caused by environmental change, requires the correction of the δ13C data due to the effects of different contents of lipids in the organic matter, differences in biogeochemical carbon cycling, varying contributions of gymnosperms versus angiosperms to peat formation, and differences in δ13C of atmospheric CO2. The resulting carbon isotope record of coal generally co-varies with the estimated variability in mean annual temperatures during the Tertiary, based on paleobotanical data. Changes in humidity and pCO2 may be responsible for deviations between the isotopic trend and the paleotemperature curve during the Miocene. The obtained temperature coefficient for δ13C of C3 plants of about 0.3‰/°C is in agreement with the results of previous studies.