<i>Pediastrum</i> in Lake Sediment and Its Mineralization

Abstract

A lot of algae fossils were found in Cenozoic lake sediments, especially Pediastrum fossil sedimentary deposits in some places of China and also in some nearby seacoasts. For imitating Pediastrum mine ralization in lake sediments, several species of Pediastrum are cultured using BBM medium and sea water with 18% salt. By optical and electronic microscope observation and photosyntheic pigment analysis, we found that Pediastrum boryanum, P.duplex var clathratum and P.tetras , etc. cannot grow well in sea water. If cultured in saline medium, the specimen will die in a short period of time. We consider that probably the Pediastrum fossil that appeared in marine sediments were transported to the sea by river. In order to prove the mineralization condition of in living organism and fossils of Pediastrum, the following analysis is made. The fat soluble substances are high and they contain a small amount of alkane, alkene fatty acid and a great deal of plant pigments. Pediastrum has high H/C and low O/C (atom number ratio) value. Therefore, it is a good resource of oil formation. The products of oxidative degradation of the insoluble cell wall of Pediastrum are similar to the production obtained by kerogen, which is known to be of algal origin. So, the insolable materials of cell wall are probably a source of kerogen during the deposition.