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961.
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963.
长江口北槽柱状沉积物粒度分布特征及沉积环境指示意义 总被引:3,自引:0,他引:3
为了研究长江口北槽深水航道的泥沙回淤机制及来源,通过对长江口北槽深水航道中部南、北导堤两侧坝田区域所采浅钻柱状样的沉积物特征、粒度参数特征、粒度成分和沉积速率特征等的分析,探讨北槽深水航道水动力条件和泥沙沉积环境。结果显示,柱状样以黏土质粉砂为主,受径流和潮汐作用,分选性都较差,偏态均为正偏,北导堤和南导堤两侧柱状样的分选系数、偏态和峰态在同一侧相互之间的特征较一致,且三组分组成接近;南北导堤异侧之间的粒度特征差异较为明显,北导堤一侧的平均粒度比南导堤的小,北导堤坝田附近的柱状样粒级百分比在垂向上波动变化较大,南导堤则表现的较为单一;南北导堤的敏感组分主要集中在粒级100μm部分。结合资料和测年数据,综合得出,由于北导堤和南导堤的涨落潮不对称,导致了其粒度特征上的不同;北槽淤积中的流域供沙逐渐减少,泥沙来源逐渐转变为滩槽交换供沙为主;北槽受深水航道工程影响巨大,泥沙沉积过程复杂,还需深入研究。 相似文献
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965.
Dawei Lv Mingzhen Zhang Huiyong Wang Guangzeng Song Ziqun Zhou Yanru Meng Penglin Yong Qing Yang 《Arabian Journal of Geosciences》2016,9(3):228
Qingdong Sag is a potential area for oil and gas exploration in Bohai Bay Basin of Northern China. In order to find a direction for the subsequent exploration of Jiyang Depression, oil and gas accumulation conditions of Qingdong Sag are studied in details by using geochemistry, sequence stratigraphy, sedimentology, and petroleum geology methods, integrated with geological, seismic, and testing data. The results show that the Shahejie Formation in the Qingdong Sag was mainly deposited in deltaic and lacustrine settings. The upper part of member 4 of the Shahejie Formation formed in delta, beach bar, low stand fan, and submarine fan. Three tectonic settings (extensional, strike-slip, and extension and strike-slip compound) were recognized. Accumulation of oil and gas in Qingdong Sag is influenced by structures and reservoir and cap rock conditions. Six oil and gas accumulation systems were found, which are north fault terrace-north subdepression oil and gas accumulation system, west slope belt and gas accumulation system, middle Horst oil and gas accumulation system, south Horst oil and gas accumulation system, drape structural belt of Qingdong 2 well oil and gas accumulation system, and Qingnan area oil and gas accumulation system. Members 3 and 4 of the Shahejie Formation are the main target of hydrocarbon source rocks because the organic matter abundance is up to the standard of good hydrocarbon source rocks. The north of the Qingdong Sag and second slope-break belt should be the key objectives of exploration in the future. 相似文献
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968.
JIA Qiuhuan SUN Qing XIE Manman SHAN Yabing LING Yuan ZHU Qingzeng TIAN Mingzhong 《《地质学报》英文版》2016,90(2):738-748
We present n-alkane distributions in the soil samples along a transect from Lhasa on the Tibetan Plateau to Bharatpur in Nepal, which covers a large geographical area and a wide range of climatic conditions. These data allow us to assess the significance of n-alkane distributions in different vegetation types and their relationships to temperature and precipitation. In the tropical rainforest and broadleaved forest zones, n-alkanes exhibit a bimodal distribution pattern with dominant homologues around n-C_(31) and n-C_(23). The bimodal distribution of tropical rainforest n-alkanes may be a general pattern because of the presence of many lianas, epiphytic plants, algae and the strong microbial activity and degradation involved in the postdepositional process. In the warm-temperate mixed forest and needle-leaved forest zones, the long-chain alkanes have a pattern of n-C_(31) n-C_(33) n-C_(27). In the alpine shrub and grassland zone, although the most abundant homologue is n-C_(31) , relatively high n-C_(23) concentrations have also been observed in some samples. The statistical results show a good correlation between n-alkane proxies and climatic factors. The average chain length(ACL) values are positively correlated with precipitation and temperature across the transect. The carbon preference index(CPI) values show a negative correlation with temperature and precipitation along a Lhasa–Bharatpur transect. Although there is a positive relationship between ACL and temperature, it is difficult to separate the two climatic variables(temperature and precipitation) because they are well coupled in the monsoon region. 相似文献
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970.
Using model results from the first phase of the Pliocene Model Intercomparison Project (PlioMIP) and four experiments with CAM4, the intensified African summer monsoon (ASM) in the mid-Piacenzian and corresponding mechanisms are analyzed. The results from PlioMIP show that the ASM intensified and summer precipitation increased in North Africa during the mid-Piacenzian, which can be explained by the increased net energy in the atmospheric column above North Africa. Further experiments with CAM4 indicated that the combined changes in the mid-Piacenzian of atmospheric CO2 concentration and SST, as well as the vegetation change, could have substantially increased the net energy in the atmospheric column over North Africa and further intensified the ASM. The experiments also demonstrated that topography change had a weak effect. Overall, the combined changes of atmospheric CO2 concentration and SST were the most important factor that brought about the intensified ASM in the mid-Piacenzian. 相似文献