AMS14C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-siz...AMS14C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600-1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750-850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study.展开更多
A new approach to the basic composition char- acter of deep sea sediment is discussed in this paper for indi- cating its paleoenvironment meaning. For this purpose high precision grain size character of sediments from...A new approach to the basic composition char- acter of deep sea sediment is discussed in this paper for indi- cating its paleoenvironment meaning. For this purpose high precision grain size character of sediments from core NS93-5 was analysed by using the Laser Diffraction Particle Size Analyzer, combining with results of micropalaeontologic counting and trace element and calcium carbonate testing, to illustrate some main grain size indexes and their relationship with micropalaeontologic makeup and terrigenous input. It was showed that the grain sizes of deep sea sediment may reflect materials properties and their buildup framework. There are obvious relations between indexes of grain size ranges and abundances of different micropalaeontologic groups and terrigenous matters, in which grain size of <2 μm represents terrigenous composition, that of >5 μm is mainly made up of various microfossil shells, except for containing volcanic dust layers, and median diameter (MD) of grain size may be taken as proxy of paleoproductivity or paleoecologi- cal dynamic. These index and proxy were consistent with micropaleontologic records for well indicating important features of paleoceanographic ecology, showing that the mi- cropalaeontologic growth in the southwestern slope area of the South China Sea (SCS) was negatively correlated to ter- rigenous input since late Pleistocene and corresponded to glacial-interglacial global climatic changes incompletely, but had a regional particularity in this sea area.展开更多
基金sponsored by a innovation fund from IOCAS(Grant No.L61022811)the Chinese Academy of Sciences Pilot Project of the National Knowledge Innova-tion Program(Grant No.KZCX3-SW-220).
文摘AMS14C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600-1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750-850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study.
基金This work was supported by the Knowledge In-novation Project of the Chinese Academy of Sciences(Grant No.KZCX3-SW-220)the National Natural Science Foundation of China(Grant No.40476024)+1 种基金the National Key Project for Basic Research of China(Grant No.2000078500)the Ministry of Science and Tech-nology of China(Grant No.2003DEA6N041).
文摘A new approach to the basic composition char- acter of deep sea sediment is discussed in this paper for indi- cating its paleoenvironment meaning. For this purpose high precision grain size character of sediments from core NS93-5 was analysed by using the Laser Diffraction Particle Size Analyzer, combining with results of micropalaeontologic counting and trace element and calcium carbonate testing, to illustrate some main grain size indexes and their relationship with micropalaeontologic makeup and terrigenous input. It was showed that the grain sizes of deep sea sediment may reflect materials properties and their buildup framework. There are obvious relations between indexes of grain size ranges and abundances of different micropalaeontologic groups and terrigenous matters, in which grain size of <2 μm represents terrigenous composition, that of >5 μm is mainly made up of various microfossil shells, except for containing volcanic dust layers, and median diameter (MD) of grain size may be taken as proxy of paleoproductivity or paleoecologi- cal dynamic. These index and proxy were consistent with micropaleontologic records for well indicating important features of paleoceanographic ecology, showing that the mi- cropalaeontologic growth in the southwestern slope area of the South China Sea (SCS) was negatively correlated to ter- rigenous input since late Pleistocene and corresponded to glacial-interglacial global climatic changes incompletely, but had a regional particularity in this sea area.
