【作者】 曹珂；

【导师】 王成善； 李祥辉；

【作者基本信息】 成都理工大学 ， 构造地质学， 2007， 硕士

【摘要】 自垩纪是地质历史中的一个特殊时期，被认为是典型的“温室气候”，但是这种观点仍旧缺乏来自于陆相白垩纪沉积的证据。四川盆地是中国白垩纪最具代表性的陆相沉积盆地之一，主要发育一套广布的红色碎屑岩沉积，且膏盐、沙漠相沉积发育。是否同人们的一般认识一样，红层、膏盐、沙漠相的出现就代表了干旱气候；温室气候下的四川盆地是否具有均一不变的气候条件；如果变化，四川盆地及其周边地区气候条件又是如何演变的。前人通过红层分子化石及沉积体系演变讨论了四川盆地边缘晚侏罗—早白垩世的古环境及古气候特征。但是盆地内部仍旧缺乏有说服力的证据。本文在前人地层古生物研究的基础上，借助粘土矿物气候指标、结合沉积物碎屑成分着重讨论了中侏罗世—古近纪早期四川盆地及周边地区的气候状况及演变过程。气候指数(F／Q)与构造指数(L／Q)分别指示了构造因素和气候因素对沉积物的影响作用。经统计分析，盆地北部边缘，中侏罗世气候因子占优势，而晚侏罗世及早自垩世早期构造因子占主导作用；盆地南部以气候因子占优势为主，说明构造活动对沉积物影响不大。粘土矿物分析参照粘土矿物组合、伊利石结晶度、伊利石化学指数三个指标。经对比发现粘土矿物主要以蒙脱石和伊利石为主。多数样品蒙脱石和伊利石同时出现，表明沉积物源区以干冷与暖湿交替的气候环境为主；局部层段只有伊利石，表明为干冷气候。同时，所有样品伊利石化学指数值均大于0.5，说明粘土矿物经历了强烈的化学风化作用，说明盆地内部为暖湿气候。更多还原

【Abstract】 The Cretaceous has been thought to be a period of "greenhouse". But there have not been enough evidences from land sediment for this viewpoint. Sichuan basin is one of the most representatives in the Cretaceous terrestrial basin, in which a group of red clastic deposition with gypsum and desert had been deposited.If sediments of redbed, desert and gypsum represent products in a arid climate as a general knowledge. Whether Sichuan basin have been in a homogeneous climate of greenhouse in Cretaceous period or not. Then how did the climate change? Some people had studied paleoenvironment and paieoelimate of basinal edge by the research of molecular fossils and evolving of depositional system. But there is no enough compellent evidences inside basin for this climate. Based on clay minerals and component of rocks, this study anlyzes the climate evoluation of in Sichuan basin in the Middle Jurassic through early Paleogene.Both climate and tectonic index can be transfered by parametes of F/Q and L/Q. Our experimental results demonstrate that the climate had been strongly influnced the sediments in Middle Jurassic but the tectonics are the main controls afterwards in the Late Jurassic along the edge of the basin. In the south of the basin, climate is the dominant factor, which implies that tectonic doesn’t extremely influence the deposition in the Middle Jurassic to early Paleogene.Proxies of clay minerals to paloeclmiate are the relative composition, crystallinity of illite, chemic index of illite. The result of experiments indicate that the main clay minerals in the redbeds are illite and smectite. Illite and smectite appear together in most samples. It implies that climate of the sourc area is mostly cool and arid. But there is only illite in sediments of Early Cretaceous and K/T boundary interval, which sugguests a warm and wet climate exisitance. Chemical index of illite of all samples are over 0.5, which indicate all clay minerals have been processed by strong chemical weathering. Consequently, climate in the basin had been in warm and wet.更多还原