On the initial material of organic matter of the Baltic Dictyonema shales

Coal petrography and micropaleophytology were used to investigate the initial material of organic matter of thiэ Baltic Lower-Eocene dictyonema shales. Microscopic examination of , dictyonema shales microsections revealed planktonic Dictyonema and their attritus, rare inclusions of tallomoalginite, as well as numerous, unanalyzable fine light lines, 10-15 mkm in thickness and 40-120 mkm in length. Micropaleophytological investigation of dictyonema shales exposed а rich and diverse complex of planktonic microfossils which served as the initial material of their organic matter. The complex is abundant in microphytofossils and Leiosphaeridia Eisenack. The first are represented bу at least 14 types of the subgroups Sphaeromorphitae, Hercomorphitae, Acanthomorphitae and Diacromorphitae, with Leiosphaeridia minutissima (Naum.) prevailing. Green algae of the type Tasmanites and cyanobacteria of the type Gloeocapsomorpha are present in lower quantities. The residues of Acrita obviously accumulate microcomponents not identified Ьу microscopic examination of microsections, while those of green algae and cyanobacteria are determined as tallomoalginite. Consequently, judging Ьу the initial material composition of their organic matter dictyonema shales are dictyonema-microphytofossils rather than dictyonema. According to G. К. Khrustaleva's classification (1987) they may belong to zoophytoplanktonites. In sedimentation basins where accumulation of dictyonema slits took place zoobenthos was not present (Berry, 1984). In the main genetic characteristics dictyonema shales entirely differ from the, Baltic Middle-Ordovician kukersite investigated earlier whose residues of phytoplankton are amazingly homogeneous and are represented also exclusively bу cyanobacteria of the type Gloeocapsomorpha. Low quantities of microphytofossils are also present (Lapo, Mikhailova, 1986). Unlike dictyonema shales, the contribution of benthos to the formation of kukersite is establithed bу numerous findings of moss animals, trilobites and worms, as well as bу signs of bioturbation.