Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka...Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.展开更多
Based on a detailed study of the radiolarian fauna, the abundance pattern of planktic foraminifera as well as on isotope and sedimentological records, the Mid-Pleistocene climate transition as a multiple transition ph...Based on a detailed study of the radiolarian fauna, the abundance pattern of planktic foraminifera as well as on isotope and sedimentological records, the Mid-Pleistocene climate transition as a multiple transition phenomenon could be recognized at Core 17957-2 from the South China Sea. Distinct changes in the radiolarian/foraminfera ratio, the coarse fraction and the radiolarian assemblages can be related to the global climate cooling observed at the Mid-Pleistocene revolution (MPR) around 900 ka. A pronounced southward shift of the North Equatorial Current that leads to lower sea-surface temperatures in the South China Sea is documented by the shift of tropical to subtropical radiolarian assemblages at 900 ka. Increasing radiolarian abundance after the MPR can be interpreted as a result of stronger upwelling and nutrient supply. These abrupt variations could result from the northern trade wind system and East Asian monsoon circulation.展开更多
Based on a quantitative radiolarian analysis, 5 radiolarian zones (NR1-NR5) have been defined at Core 17957-2 from the South China Sea, considering radiolarian zonations from low latitudes. The absolute age assignment...Based on a quantitative radiolarian analysis, 5 radiolarian zones (NR1-NR5) have been defined at Core 17957-2 from the South China Sea, considering radiolarian zonations from low latitudes. The absolute age assignment of the radiolarian zones and the ranges of the six marker species is based on the direct correlation with the paleomagnetic and isotopic record, respectively. A comparison of the radiolarian stratigraphic data obtained from Core 17957-2 from the South China Sea with those from the equatorial Pacific and the tropical Indian Ocean shows a close similarity to the ages defined in the equatorial Pacific. The obtained biostratigraphic data provide an excellent tool for further dating of Pleistocene sediments in the China Sea.展开更多
基金This project was supported by the National Natural Science Foundation of China under contract! Nos 49946011 and 49999560 by
文摘Abrupt changes in radiolarian composition are discovered over the last 600 and 120 ka B. P. based on quantitative analyses of radiolarians in ~ 17957 - 2 of the southern South China Sea. The distinct changes at 600 ka B. P. could correspond to the onset of the 100 ka cycle during the glacial and interglacial periods. This abrupt change in the 100 ka cyclicity at 600 ka B. P. occurred also in the magnetic susceptibility signal that is obtained from and paleosol sequences of the China Loss Plateau. The larger amplitude and stronger cyclicity in the susceptibility signal after 600 ka B. P. reflect the prominent change in the intensity of the monsoon, induced by an enhancement of the momsoon circula- tion. Stronger seasonality during the glacial period in the South China Sea, resulted from strengthening of winter monsoon, might lead to the changes in the radiolarian composition at 600 and 120 ka B. P. It can be suggested that only species adapted to a broader temperature range might have been able to live in this environment. Therefore, the abrupt changes in radiolarian composition at 600 and 120 ka B. P. could be attributed to the stronger so differences between summer and winter that were caused by the striking change in the intensity of the monsoon circulation.
文摘Based on a detailed study of the radiolarian fauna, the abundance pattern of planktic foraminifera as well as on isotope and sedimentological records, the Mid-Pleistocene climate transition as a multiple transition phenomenon could be recognized at Core 17957-2 from the South China Sea. Distinct changes in the radiolarian/foraminfera ratio, the coarse fraction and the radiolarian assemblages can be related to the global climate cooling observed at the Mid-Pleistocene revolution (MPR) around 900 ka. A pronounced southward shift of the North Equatorial Current that leads to lower sea-surface temperatures in the South China Sea is documented by the shift of tropical to subtropical radiolarian assemblages at 900 ka. Increasing radiolarian abundance after the MPR can be interpreted as a result of stronger upwelling and nutrient supply. These abrupt variations could result from the northern trade wind system and East Asian monsoon circulation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 49291100)by the German Federal Ministry for Education, Science, Research and Technology (BMBF) as part of a German/Chinese scientific cooperation Program. This is Alfred
文摘Based on a quantitative radiolarian analysis, 5 radiolarian zones (NR1-NR5) have been defined at Core 17957-2 from the South China Sea, considering radiolarian zonations from low latitudes. The absolute age assignment of the radiolarian zones and the ranges of the six marker species is based on the direct correlation with the paleomagnetic and isotopic record, respectively. A comparison of the radiolarian stratigraphic data obtained from Core 17957-2 from the South China Sea with those from the equatorial Pacific and the tropical Indian Ocean shows a close similarity to the ages defined in the equatorial Pacific. The obtained biostratigraphic data provide an excellent tool for further dating of Pleistocene sediments in the China Sea.
