LATE QUATERNARY SEDIMENT PROVENANCE AND PALAEOENVIRONMENT IN LIAODONG BAY, BOHAI SEA: EVIDENCE FROM DETRITAL MINERALS AND AUTHIGENIC PYRITE

Detrital minerals of a 50.1 m-long sediment core (LDD7) from the Liaodong Bay (LDB), the Bohai Sea were analyzed to investigate light/heavy mineral assemblages and sediment provenance of the sediments, chemical weathering extent of drainage basin surrounding the LDB, and relative sea-level of the Bohai Sea in Marine Isotope Stage (MIS) 3. Major light mineral components are quartz and feldspar; plate-shaped minerals and carbonate minerals come the second. Among heavy minerals, amphibole, epidote, mica group and authigenic pyrite occupy the first place; metal minerals, garnet and sphene take the second place. Coarse components of the core come from multiple sources, which mainly include the discharges from the Liaohe, Luanhe and Huanghe Rivers. As the characteristic minerals of the Huanghe River, the abundance of carbonate minerals indicate that the Huanghe River greatly influenced the core during the low sea-level stages. Ratio of quartz/feldspar, ZTR index of the very stable heavy minerals and ATi index of the apatite, which are correlated to each other to some extent, can roughly reflect the chemical weathering extent of the drainage basin. However, the impact of sediment source on these indexes should not be ignored. Authigenic pyrite, which correlates with a reducing environment, is concentrated in alluvial flat, lacustrine and tidal flat facies with low hydrodynamic force and enriched organic matter. Considering that the scatter points of age versus depth of cores from the Bohai Sea are distributed above the average relative sea-level curve of the world during MIS 3, together with the considerations of depositional water depth, tectonic subsidence and sediment compaction, relative sea-level of the Bohai Sea maybe higher than the world sea-level in MIS 3.