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

This paper analyses the distribution of pollen in the surface sediments of the South China Sea as recorded in 28 samples from the area 6 degrees 09'-2 0 degrees 07'N and 112 degrees 05/-119 degrees 45'E, at water depths of 329 -4307 m. Pollen concentrations range from 444 kgrains/g (dry wt) on the low er part of the continental slope in the northeast to zero in the central ba sin below 4000 m water depth. Pollen distribution patterns in the concentra tion and percentage isopolls (incorporating data from the literature) refle ct the routes and mechanisms of pollen transport, pollen source areas and c onsiderable systematic differences between north and south. The northern SC S is distinguished by very high concentrations due to the high production a nd effective long-distance transport of pine pollen and fern spores. The ma ximum of their concentration occurs in the north, adjacent to the convergen ce of the Bashi and Taiwan Straits, rather than near the estuaries of big r ivers, and stretches as a saddle from NE to SW, consistent with the directi on of the NE winter monsoon and sea current. This pattern implies that pine pollen and fern spores, adapted to wind transport and water flotation, com e from the northeast through the straits borne on the winter monsoon and se a current forced by it. Their source areas should cover lame regions, proba bly including south and southeast China. Most pollen of tropical and subtro pical broad-leaved trees found in the northern part of the SCS occur in low concentrations, however, these concentrations decrease uniformly offshore, implying a fluvial discharge from nearby lowlands in South China. In the s outhern part of the SCS, pollen of tropical and subtropical broad-leaved tr ees predominate. Total pollen concentrations, however, are much lower, only 1/10 of those of the northern part. The greatest concentrations occur offs hore north Borneo and decrease toward deep water, suggesting fluvial input from relatively local sources on the adjacent islands (e.g. Borneo). (C) 19 99 Elsevier Science B.V. All rights reserved.