干旱区生态环境知识资源中心

Meromictic Shira Lake is situated in the semi-arid climatic area of South Siberia. The lake has a size of 5 x 9 km and a maximum depth of 24 m. A sediment column of 155 cm in length was retrieved in the deepest part of the lake. The sediment has thin laminated structure, where black clay carbonate organic-bearing layers are coupled with white organic free ones. Thickness of coupled rhythms varied from 2 mm in the uppermost 20 cm of core to 0.4 mm close to the bottom. For calculation of the layers were used pictures of wet core, optical thin sections and geochemical indicators, marking each annual layer. For dating the depth of the core were used AMS data C-14 content, the activity of Cs-137 and Pb-210. Comparison of age model, obtained by counting annual layers with radiocarbon data, showed that the reservoir effect in Lake Shira is equal 1275 years. Radiocarbon data reduction by this amount gives a good coincidence all results.