Skład materii organicznej jako wskaźnik genezy osadów jeziora Sarbsko

Abstract

Organic matter composition as an indicator of genesis of Lake Sarbsko sediments.A b s t r a c t. In the study the applicability of some organic geochemical indices in paleoenvironment reconstruction in highly dynamic coastal basin was assessed. Within the frame of the study 9 samples from the profile Sa1/2, representative for Lake Sarbsko, were investigated. Bulk organic geochemical parameters (TOC/TN, TOC/TS, HI, δ13CTOC) and molecular composition of selected hydrocarbons were used to recognize variations in paleosalinity, to determine origin of organic compounds as well as to demonstrate diagenetic alterations of the sediments. Fluctuations of salinity during the lake evolution are reflected by changes in TOC/TS and steroid/hopanoid ratios as well as δ13CTOC values. Anoxic conditions of sedimentation correlate with low values of pristane/phytane ratio and extended microbial acitivity is mirrored by elevated contribution of hopanoids in the samples. Organic matter in Lake Sarbsko sediments originated from both enhanced biological productivity in the water column and terrestrial sources. It was shown, that organic geochemical indices are a complementary method for reconstruction of salinity, as there is satisfactory correlation between different organic and inorganic geochemical proxies. On the other hand, early diagenesis and complex mechanisms delivering organic matter to coastal basins hinder interpretations of origin of organic compounds.