Sedimentary feature on Borsog Bay, eastern shore of Lake Khuvsgul in Northern Mongolia

This study reports on the sedimentary characteristics of Lake Khuvsgul which is located at the southern end of the Baikal Rift System within the continental interior of East Eurasia. With an elevation of 1645 m a.s.l., it has a climate that is mainly controlled by the Siberian-Mongolian high pressure system and the westerly wind systems from the Atlantic Ocean. Lake Khuvsgul, Mongolia’s second largest lake by surface area (2760 km2), is the country’s deepest fresh water lake with a bottom that is only 262 m a.s.l. Fed by 96 rivers and streams, it is drained by the Eg River which, after joining the Selenge River, fl ows into Lake Baikal. Analysis of a 12.3 m core from Borsog Bay near the eastern shore of the lake indicates a sedimentation rate of about 0.08 cm/a. It is believed that this relatively high sedimentation rate is due to the large sedimentary input from River Borsog and the variability of the turbidity currents at depths shallower than 9 m. It further suggests that the large sedimentation rate may be correlated with the annual and seasonal variations in the dominant westerly wind system over the Siberian Plateau. Such variations have resulted in a lowering of lake level and impacted the rate of erosion within the river’s catchment area and therefore the sediment input to the lake. Because this is a preliminary report, further research into the sedimentary dynamics within Lake Khuvsgul and the role played in those dynamics by the climatic variability over Mongolia and Central Asia is planned.

W pracy przedstawiono charakterystykę osadów dennych w zatoce Borsog na Jeziorze Khuvsgul w północnej Mongolii. Właściwości fizyczne i chemiczne osadów określono na podstawie próby o miąższości 12,3 m, którą podzielono na 1233 próbki. Datowanie wieku poszczególnych warstw osadów wykonano na podstawie zawartości izotopu węgla 14C. Stwierdzono, że osady na głębokości 12 m pod powierzchnią dna zatoki mają około 7800 lat, a średnie tempo przyrostu miąższości osadów wynosi 0,08 cm·rok–1. Na podstawie analizy tempa przyrostu poszczególnych warstw osadu oraz zmienności ich właściwości fizycznych i chemicznych stwierdzono, że występuje duża zgodność przebiegu procesu sedymentacji osadów w zatoce Borsog z lokalnymi zmianami klimatu.