MINERAL MAGNETIC STUDY OF LATE QUATERNARY SOUTH CASPIAN SEA SEDIMENTS- PALEOENVIRONMENTAL IMPLICATIONS

Magnetic properties of sediments from a core (10 m long) in the southe rn basin of the Caspian Sea have been investigated. Varying concentrat ions of greigite (Fe3S4) dominate the magnetic fraction in Late Pleist ocene sediments. The synsedimentary formation of greigite indicates th at the Late Pleistocene Caspian Sea was a brackish or fresh-water, poo rly ventilated basin and suggests a water level higher than at the pre sent. The variation in magnetic parameters, with the detrital magnetit e-bearing fraction remaining constant, is interpreted in terms of grei gite grain-size variation and related to the slight variation in water salinity. The Holocene sediments are characterized by detrital magnet ite. This indicates better ventilation of the basin and suggests lower water levels than in the Late Pleistocene. The gradual change in magn etic properties of the sediments between 90 and approximate to 60 cm d epth, with decreasing quantities of greigite, indicates stepwise estab lishment of oxic conditions in the Holocene.