Carpathian Journal of Earth and Environmental Sciences

This study is focused on the lithological pattern of the sediment composition, trying to distinguish the causes of the local sedimentary processes and the differences in terms of hydrological andhydro-biogeochemical particularities. Sediment grab and sediment core samples from 7 lakes located within the Danube Delta were analyzed for the main sediment components: organic matter, carbonate sand minerogenic/siliciclastic material. The vertical and areal distribution of the lithological components was studied, in order to establish the main factors which influenced the lacustrine sedimentation in time and in space. As a general remark, there is a constant inverse correlation between the siliciclastic fraction and the organic matter, the main sediment components, and only a minor participation of the carbonate minerals. The results indicate that the distribution of organic matter in sediments is mainly influenced by the in-situ organic fluxes and less by the input derived through the hydrological network. The position more or less protected of the lakes within the Delta in relation to the Danube River inputs controls the sediment composition: the lakes directly influenced by the direct riverine inflows contain more siliciclastic sediments as compared with the more confined lacustrine areas, characterized by sediments very rich in organic matter. The carbonates distribution shows relatively low amounts and probably their contents are related to some biochemical processes occurring inside the lake.