Mineral magnetic study of Late Quaternary South Caspian Sea sediments: palaeoenvironmental implications

SUMMARY Magnetic properties of sediments from a core (10 m long) in the southern basin of the Caspian Sea have been investigated. Varying concentrations of greigite (Fe 3 S 4 ) dominate the magnetic fraction in Late Pleistocene sediments. The synsedimentary formation of greigite indicates that the Late Pleistocene Caspian Sea was a brackish or fresh-water, poorly ventilated basin and suggests a water level higher than at the present. The variation in magnetic parameters, with the detrital magnetite-bearing fraction remaining constant, is interpreted in terms of greigite grain-size variation and related to the slight variation in water salinity. The Holocene sediments are characterized by detrital magnetite. This indicates better ventilation of the basin and suggests lower water levels than in the Late Pleistocene. The gradual change in magnetic properties of the sediments between 90 and #60 cm depth, with decreasing quantities of greigite, indicates stepwise establishment of oxic conditions in the Holocene.