Abstract:

During the sporopollen and algae research of the deep-sea sediments at Core 69 in the South China Sea, five sporopollen zones have been distinguished in ascending order as Zone 1 (552.5—470 cm): Quercus (evergreen)-Pinus-Cyathea-Artemisia, Zone 2 (470—350 cm): Pinus-Podocarpus-Quercus-Polypodiaceae, Zone 3 (350—250 cm): Quercus (evergreen)-Castanopsis-Pinus-Polypodiaceae, Zone 4 (250—140cm): Pinus-Podocarpus-Artemisia-Polypodiaceae, and Zone 5 (140—0 cm): Podocarpus-Cyathea-Quercus (evergreen)-Pinus-Polypodiaceae. The sporopollen zones reflect three evolution stages of vegetation, climate and paleoenviornment in the South China Sea since 64 000 yr BP as follows: hot and wet tropical monsoon rainforest, semievergreen monsoon rainforest of northern tropics, and return to hot and wet tropical monsoon rainforest. Stage 1: During this period, the vegetation was characterized by tropical monsoon rainforest，reflecting a hot and wet climate when the sea level rose. There were many evergreen tree species. The tree layer was dominated by Dacrydium, Podocarpus, evergreen Quercus, Pinus, Elaeocarpus, Magnolia, Castanopsis, Palmae, Myrica and Altingia, among others. The herbage layer under canopy included Gramineae, Artemisia，Chenopodiaceae and Cyperaceae. The ferns were dominated by Polypodiaceae, Microlepia, Cyathea, Diplopterygium and Pteris. Mangrove plants grew along the coastal areas. Stage 2: The vegetation was semievergreen monsoon rainforest of northern tropics. This stage was indicated by the palynological Zones 2 to 4. The elements of evergreen Quercus, Castanopsis, Pinus and Magnolia from the southern subtropical zone increased in the vegetation, whereas the elements of Elaeocarpus, Dacrydium and Palmae from the tropical zone decreased. The herbage layer under canopy consisted of Gramineae, Artemisia and Cyperaceae, among others. The ferns were dominated by Polypodiaceae, Pteridium, Cyathea, Diplopterygium and Adiantum. Mangrove plants grew along the coastal areas. The vegetation was characterized by the northern tropical semievergreen monsoon rainforest, reflecting a slightly dry and warm climate when the sea level dropped. Stage 3: The vegetation was again tropical monsoon rainforest. Indicated by palynological Zone 5, the vegetation mainly consisted of Dacrydium, Podocarpus, Altingia, Palmae, Lauraceae, Magnolia, Sapindaceae, evergreen Quercus, Castanopsis and Myrica, among others. The herbage layer under canopy was dominated by Gramineae, Umbelliferae, Chenopodiaceae and Artemisia. The ferns included Polypodiaceae, Cyathea, Dicranopteris, Diplopterygium and Pteris. Mangrove plants grew along the coastal areas. All of these showed a hot and wet environment when the sea level rose. Combined the sporopollen and algae data with oxygen isotope dating, a stratigraphic division was done for the Core 69 in the South China Sea. Palynological Zone 1 corresponds to oxygen isotope period 3, and its stratigraphic time is Q33—2; Palynological Zones 2 to 4 correspond to oxygen isotope period 2, and its stratigraphic time is Q33—3; Palynological Zone 5 corresponds to oxygen isotope period 1, and its stratigraphic time is Q4.

Key words: the South China Sea, palonological record, paleoclimate