Isotope Studies of the Caspian Sea: Climatic record from bottom sediments (preliminary results)

摘要

Two cores (7.8 m and 9.3 m long) of bottom sediments from the southern and middle Caspian Sea were studied. Variation of the stable isotopes of oxygen and carbon in the carbonates, radiocarbon dating, lithological structure and distribution of the main salt ions Cl~-, Na~+, and K~+ along the core length were used to develop a general picture of the relationship between water level fluctuation and climatic change in the sea basin within the last 70 ka. It was found that during the glacial ages the sea level dropped as far as the Apsheron sill, and the southern and middle parts of the sea were separated. At the time of interglacial episodes, when the southern and northern glaciers melted, the water level rose and both sea basins merged. It was determined that about 40 ka BP, during the Khvalinean transgression after the Ostashkov episode of the Valday (Wurm) glaciation, the Caspian Sea discharged to the Black Sea through the Kuma-Manych Valley (25 m a.s.l.).