Zawartość i skład izotopowy węgla organicznego z utworów formacji poznańskiej (miocen–pliocen) z rejonu Konina (środkowa Polska : sugestie paleośrodowiskowe i stratygraficzne

The paper presents interpretation of total organic carbon (TOC) content and carbon isotopic composition of organic matter within the Miocene/Pliocene Poznań Formation deposits recorded in BK 110 borehole in the Konin area (Central Poland). The TOC content as well as a :13C(TOC) PDB values vary widely throughout the deposits, from 0.1% to 6.1% (0.6% at average) and from –14.2‰ to –26.2‰ (–23.2‰ at average), respectively. The distribution of these parameters within the series allow to distinguish the lower part, which is thinner and enriched in organic matter accumulation, and the upper part, which is thicker and clastic. The a:13CTOC values indicate that C3 plant material prevailed in the lower part, while the upper part contains of C3+C4 plant material or C3 + marine organic matter. The subdivision of the Formation into lower and upper parts reflects a shift from peat-bog vegetation in nearshore lake into brackish lagoon environment with a periodical supply of terrigenous land material. The shift in the origin of the organic matter and sedimentological features of the Poznań Formation sediments imply a tectonic event or/and climatic shift, possibly connected with evolution of plants population and thus relative decrease in C3 and increase in C4 organic material at the Miocene– Pliocene boundary.