Cyclic water level oscillations of the KaraBogazGol-Caspian Sea system

摘要

The KaraBogazGol (KBG) water level oscillations were reconstructed in the last 200 years using the geochemical evolution of the uppermost meter of its sedimentary infill. High-resolution studies of the mineralogical composition of the KBG sediments show alternating periods of high concentration brines followed by periods of more dilute waters. The relative water level reconstruction was based on statistical models (factor analysis (FA), correspondence analyses (CA) and detrended correspondence analyses (DCA)) whilst the chronological framework was established using the ~(210)Pb technique. This reconstruction was compared with the instrumental water level record of the Caspian Sea, showing a high degree of correlation (r~2 = 0.83). The agreement between the reconstructed and the measured water level oscillations of the Caspian Sea indicates that environmental changes can be reconstructed from closed lakes provided that an accurate chronological control of sedimentary processes is available. The water level reconstruction shows that the Caspian Sea water level fluctuations follow a cyclical pattern rather than an 'erratic' one, as has been suggested in the literature. Two main periodicities of 62.5 and 38.46 years have been found.