Pollen distribution in hemipelagic surface sediments of the South China Sea and its relation to modern vegetation distribution

摘要

This paper analyses the distribution of pollen in thesurface sediments of the South China Sea as recorded in 28samples from the area 6°09'-20°06'N and 112°05'-119°45'E,at water depths of 329-4307m. Pollen concentrations rangefrom 444 kgrains/g (dry wt) on the lower part of the continentalslope in the northeast to zero in the central basin below 4000mwater depth. Pollen distribution patterns in the concentration andpercentage isopolls (incorporating data from the literature) reflectthe routes and mechanisms of pollen transport, pollen source areasand considerable systematic differences betweennorth and south.The northern SCS is distinguished by very high concentrations dueto the high production and effective long-distance transport of pinepollen and fern spores. The maximum of their concentrationoccurs in the north, adjacent to the convergence of the Bashi andTaiwan Straits, rather than near the estuaries of big rivers, andstretches as a saddle from NE to SW, consistent with the directionof the NE winter monsoon and sea current. This pattern impliesthat pine pollen and fern spores, adapted to wind transport andwater flotation, come from the northeast through the straits borneon the winter monsoon and sea current forced by it. Their sourceareas should cover large regions, probably including south andsoutheast China. Most pollen of tropical and subtropical broad-leaved trees found in the northern part of the SCS occur in lowconcentrations, however, these concentrations decrease uniformlyoffshore, implying a fluvial discharge from nearby lowlands inSouth China. In the southern part of the SCS, pollen of tropicaland subtropical broad-leaved trees predominate. Total pollenconcentrations, however, aremuch lower, only 1/10 of those of thenorthern part. The greatest concentrations occur offshore northBorneo and decrease toward deep water, suggesting fluvial inputfrom relatively local sources on the adjacent islands (e.g. Borneo).