МЕХАНИЗМ ОБРАЗОВАНИЯ, ВОЗРАСТ И ЭВОЛЮЦИЯ ОЗЕРНЫХ КОТЛОВИН ЦЕНТРАЛЬНОЙ ЧАСТИ ПСКОВСКОЙ НИЗМЕННОСТИ, "Геоморфология"
2018
Lake Belaya Struga, Lake Bolshoe, Lake Chernoe are located in the central part of Pskov Lowland, on both sides of the Luga stage marginal formations (the Late Valday ice sheet) and confined to the different genetic types of relief. Analyses of the lake sediment lithology in borehole cores and the position of lakes in the relief allowed to reconstruct the mechanism of lake basin formation and to mark main stages of the evolution of the lakes in the Late Glacial time and Holocene. The formation of lake basins within limnoglacial plains is associated with uneven glacier accumulation in condition of melting of dead ice and the activity of proglacial lakes. The isolation of such lakes occurred in the period from 14.4 to 13.8 ka BP. The formation of lake basins within outwash plains was due to the subsidence and glacio-karst mechanism. The lacustrine stage of sedimentation in the basins of this type is associated with the beginning of the Alleroed (in Lake Chernoe no later than 13140 ± 250 ka BP). Radiocarbon dating helped to locate the Late Pleistocene – Holocene boundary in the lacustrine sequence, to estimate the age of lacustrine sediments at different depths and the rates of their sedimentation. The values of loss on ignition at 550 and 1000 °C indicate: the minerogenic type of sedimentation prevailed in all lakes during the Late Glacial time and in Lake Belaya Struga during the Holocene; the organogenic type dominated in the Lake Chernoe and Lake Bolshoe during the Holocene. It was established that the highest sedimentation rates in lakes occurred n the Atlantic period of the Holocene. The remaining lifetime of the lakes (duration of time until the overgrowning with aquatic plants and turning into swamps) was estimated on the basis of the average rates of sedimentation in the last 5–7 ka (0.2 to 0.3 mm/ year) and is approximately as follows: Lake Chernoe – 5500 years, Lake Belaya Struga – 10800 years, Lake Bolshoe – 3500 years.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
8
References
0
Citations
NaN
KQI