| With rapid development of economy and urbanization in recent years, the detailed information on geologic environment is needed urgently in the eastern Yangtze delta, and specially the change about geologic environment and strata development during Quaternary Period are demanded to hold in Yangtze estuary.Based on analysis of lithology, palynology, micropaleontology , palaeomagnetism, chronology , the palynology and foraminifer series are analysed from the sediment core of MZ at Chongming island. By high-resolution research of palynology and foraminifer series, the palynology and foraminifer sequence are established in order to reveal the process of vegetational succession, climatic fluctuation, and changes of sea level.The emphasis is to find environmental events that impact climatic change and environmental evolvement in the study area. Based on that, combined with chronology data, the strata is divided and contrasted with the near region. The paleogeographic environment at Yangtze estuary is re-established. The main conclusions are as follows:The palynology series established based on palynology data is divided 9 sporo-pollen belts, which is further divided 19 sporo-pollen subzones. The climatic character is different from others according to spore-pollen series in the Quaternary Period. That is to say, there are some kinds of semitropical pollen that do not disappear despite of less quantity. As a whole, the temperature fluctuation was great, but that of precipitation was little in the Quaternary. The climate was cold and dry in Early Pleistocene, then it was better in Middle Pleistocene, and it got warm and wet in Late Pleistocene, including the phases that were cold-dry, and fluctuated between dry and wet. Four climatic fluctuations are revealed in Holocene.Transforming sporo-pollen data from MZ borehole as an aid in setting up pollen-climate transfer functions The Quaternary sequence about mean annual temperature is reestablished, by use of the factor analysis based on modern and fossil pollen data. The climatic fluctuation was not distinct during early and middle of the Quaternary, and then its mean annual temperature were below that of) the present (from 2600 to 780 kaB.P., the mean annual temperature was 14.8℃; from 780 to 110 kaB.P, the mean annual temperature was 15.0℃). From then on , the change of temperature greatly fluctuated four times: raising in fluctuations(from 110 to 40.4 kaB.P., the mean annual temperature was 15.6℃ ) , declining (from 40.4 to 20.5 kaB.P., the mean annual temperature was 15.5℃),rising and keeping temperaturehigh(from 20.5 to 16.3 kaB.P., the mean annual temperature was 16.7℃; from 16.3 to 8.16 kaB.P., it was 16.8℃; from 8.16 to 5.5kaB.R, it was 17.rc),falling(from 5.5 to 1.87 kaB.P., the mean annual temperature was 14.9℃), and being consistent with the present(from 1.87 kaB.R to the present, the range was from 15.2℃ to 15.8℃). A cold event occurred),(its mean annual temperature was 14.3 ℃) in 5460±220a.B.P. The climatic condition in 72870±4340a.B.P was similar to that of MIS 5a.The foraminifer from the upper 60meters of the core is divided 5 belts from the bottom up, based on the characteristic of The foraminifer series about the richness, simple diversity and composite diversity of foraminifer. The characteristic of The foraminifer series was similar to that of No 1 transgression and No 2 transgression in the Quaternary, and the affect of No 3 transgression was revealed in terms of spore-pollen, so we find that 3 transgressions occurred in Holocene, Middle of Late Pleistocene and Early of Late Pleistocene. The transgressions of The Quaternary in Yangtze estuary was weaker than that of the northern plain of the Jiangsu Province China.There were many carbonate nodules in Early Pleistocene which shows it was cold on the whole and occurred several wet and dry fluctuations. It had responsed to Mid-Pleistocene Revolution.MZ borehole is 284.5 meter-long. According to the characteristics of rock, sedimentary structure, depositional cycle, combined with that of sporo-pollen, f...
|
PDF Full Text Request