Affiliation:
1. Institute of Geography RAS
2. Lomonosov Moscow State University, Faculty of Chemistry
3. Faculty of Geography and Geoinformation Technology, HSE
Abstract
The article discusses the first results of studying the structure of the bottom topography and bottom sediments of Chukhlomskoe Lake (Kostroma Region, Chukhlomsky District). We analyzed the lake bottom topography based on the results of our bathymetric survey and discovered two hollows with maximum depths diverging from the lake’s center towards the city of Chukhloma. The maximum depth inside the hollows (and for the entire lake) reaches 5.4 m, and the average lake depth is 2.2 m. There are two steps seen in the bottom topography; 2.0–2.4 m and 1.5–1.8 m. The bottom sediment structure of Chukhlomskoe Lake was revealed by drilling from the ice with two boreholes (with lengths of 9.45 and 7.45 m, located in the area of background depths and inside the hollow, respectively). Five radiocarbon AMS dates were obtained for the core from the hollow’s bottom. The sedimentary sequences of the pre-Holocene part of both cores show high similarity in structure and depths of the marker horizons identified by a set of lithological analyses. The structure and thickness of Holocene sediments differ significantly. In the area of background depths, the Holocene organo-mineralogenic silt is 3.8 m, and inside the hollow, the thickness of this layer is only 1.45 m. Moreover, hiatuses in sedimentation were documented in the structure of the Holocene sediment inside the hollow. The age of hiatuses, based on the sedimentary model, was estimated as 10.6–5.3 and 4.9–0.06 thousand years ago. A probable mechanism for the origin of hollows is localized erosion caused by wind currents in a highly shallow lake. An additional erosion factor can be the degassing of bottom sediments, which leads to the loosening of the bottom layer of sediments, which makes them susceptible to erosion. The cutoff of sediment erosion inside the hollow coincided in time with the construction of a dam on the Veksa River and a rise in the lake level by 1.0–1.5 m in the 1960s.
Publisher
The Russian Academy of Sciences
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