d13C OF ORGANIC MATERIAL IN PERMIAN AND LOWER TRIASSIC SEDIMENTS

High-resolution records of secular variation in d¹³C of marine biogenic carbonates have been established for the entire Phanerozoic. Due to the fact that sedimentary organic material (TOC) receives carbon from the same pool (atmosphere) as carbonates, the secular variations should be mimicked by d¹³C of TOC. As a result of different photosynthetic pathways modern terrestrial plants have variable carbon isotope signatures which are distinct from those of marine algae. Bacterial degradation and/or impregnation by migrating hydrocarbons can result in a significant overprint of the original carbon isotope signal of bulk organic matter. Therefore, a detailed characterisation of biological provenance (marine, terrestrial, bacterial) and post-sedimentary degradation of organic material is required for the interpretation of the carbon isotope signature of organic material (OM). This can be achieved by a complementary combination of organic geochemical, palynological and organic petrological techniques. For the present study we analysed marine and terrestrial organic matter of Permian and Lower Triassic age for their d¹³C signature with complementary analysis performed on several subsets of our sample collection. The temporal d¹³C record of bulk TOC clearly verifies the well-known isotope shift at the Permian Triassic Boundary. In general, the d¹³C of coals are roughly 2 ‰ higher than those of contemporaneous marine bulk TOC. However, refractory terrestrial OM may contaminate the latter. The biomarker distribution analysed by GC/MS proves the autochthonous nature of the studied OM and a moderate thermal maturity. The latter is also proven by vitrinite reflectance measurements of Permian coal samples which gave values between 0,62 und 0,65 % Rm.