ORGANIC MATTER ACCUMULATION IN BOTTOM SEDIMENTS OF LAKES OF THE KAMA-KELTMA LOWLAND (PERM CIS-URALS) IN THE LATE GLACIAL AND HOLOCENE

Abstract

In three sediment cores collected from the lakes Novozhilovo and Chelvinskoye, the organic matter content wasanalyzed by measuring the loss on ignition (LOI). The cores ranged in thickness from 2.8 to 5.2 meters. The lower part of thesediment uncovered by core NZH-1 was deposited during the Late Glacial, while cores NZH-2 and CHOL-1 covered the entire Holocene. It is for the first time that a detailed chronology of changes in lake ecosystem productivity over the past 14 ka h as beenobtained for the Perm Cis-Urals. Based on the dynamics of the organic matter content in the cores, six periods with similar sedimentation characteristics were identified. Three stages with increased accumulation of organic matter were observed in the co res: during the Bölling–Allerød Interstadial, at the beginning and in the middle of the Holocene. These periods of organic matter accumulation were mainly associated with the intensity of lake production processes which, in turn, were a result of climatic changes during the Late Glacial and Holocene. On a regional scale, paleogeographical events, such as the active restructuring of river systems, changes in runoff, and physical weathering within the lake catchment area, all contribute to changes in organogenic sedimentation rates. For the selected time periods, sediment accumulation rates were determined using Bayesian age modeling, and a correlation was found with regional changes in plant communities recorded in the palynological spectra of reference sections from the Late Glacial to Holocene.