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The bulk of sedimentary material is supplied to Lake Ladoga in the form of suspension in river water. Rivers annually deliver 1.2 Mt of sedimentary material. A significant portion of clastic material in the sedimentation basin is also related to shore and bottom abrasion. Average sedimentation rate in the lake is 0.4 mm/yr for the last 10 ka. The wide grain size spectrum of lacustrine sediments is caused by textural inhomogeneity of Quaternary rocks, which are the main source of sedimentary material. Variably-grained relict sands at the depth of 12–20 m originated during a relatively low lake level. Silt, sand, and clay at 30–75 m are formed as a result of integration of the relict and newly supplied material. The sediment composition is principally defined by Cambrian–Ordovician rocks in the southern part of the lake, morainal and postglacial deposits in the eastern part, and crystalline basement rocks and their derivatives in the northern and western parts. Textural, mineral, and petrographic transformations of the surficial sediments take place under the influence of waves, induced currents, and gyres. Waves and induced currents mainly produce mature sediments, whereas gyres lead to the integration of materials supplied from different sources and the formation of petrographicaly mixed deposits. Based on the comprehensive analysis of sedimentological information, conditions of sedimentation and main features of lithodynamics are characterized. The results obtained may serve as a basis for the creation of a conceptual model of sedimentogenesis in Lake Ladoga. 相似文献
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