Characteristics of modern pollen distribution in surface sediment samples for the northern South China Sea from three transects

Abstract

The present study is an analysis of the distribution of pollen in surface sediments of the northern South China Sea (SCS) as recorded in 74 samples from the area 12.00–23.72°N, 108.57–120.00°E at water depths of 14–4410 m. The characteristics of the pollen distribution along north–south, northeast–southwest and northwest–southeast directions in the northern South China Sea are described below: (1) Based on PCA analysis, samples in the present study are mainly dominated by river transport (Component 1). Pollen Area I has samples with Component 1 > 0, located in the east and south part of the study area, with the dominant species of Poaceae, Pinus (water-transported), Monolete Spores, Podocarpus macrophyllus, Fungi, Rhizophoraceae, Artemisia, and Castanopsis, transported by Pearl River, rivers from Taiwan Island, Mekong River. Pollen Area II has samples with Component 1 < 0, they are located in the east and south around Hainan Island, with dominant Trilete Spores, transported by rivers from Hainan Island and summer monsoon forced marine current. (2) The characteristics of the percentages of pollen grains were influenced mainly by the geomorphology of the seafloor. Pollen percentages from sample sites on the continental shelf or near islands are different from those in the sea basin. The percentages of Trilete spores at continental shelf or island sites are higher than those at sea basin sites. (3) The pollen percentages and concentrations indicate that Castanopsis and Evergreen Quercus pollen are most abundant in the southwest. These pollen could be transported from Indochina by the Mekong River. The percentage of Castanopsis pollen decreased from north to south and from northwest to southeast, indicating that the Guangdong coast is a secondary source area. Monolete spores, Cyperaceae and Poaceae abundances decreased from northwest to southeast, related to input from the Pearl River or proximity to the Guangdong coast. In the north–south direction, Monolete spores and Poaceae decreased from the north and from the south to the middle of the basin, which can be attributed to inputs from the Pearl River or Guangdong coast in the north and Indochina in the south.