摘要
龙门山中段都江堰市、彭州市、什邡县等地的侏罗系十分发育，呈ＮＥ－ＳＷ向展布。在１９９１～１９９５年１／５万区调期间，从这个地区测制的一些侏罗系剖面中划分出了千佛崖组、沙溪庙组、遂宁组和莲花口组４个岩石地层单位，并与邻区相应地层单位进行了对比，总结了它们的岩石特征和相变；根据ＥＳＲ（电子自旋共振）测年资料讨论了侏罗纪的年代地层划分；并简要叙述了千佛崖期湖相、沙溪庙—遂宁期河流相和莲花口期洪积相（冲积扇相）的划分依据。
The coastal region of modern Southeast China is called the “Zhejiang Fujian Mountainous Area”. From its northern border southward, the outer zone includes the Tiantai, Kuocang, Yandang, Jiufeng, Daiyun and Bopingling Mountains in proper order; after extending into the border of Guangdong, it also includes the Lianhua Mountain. In the inner zone are distributed, in proper order, the Huiji, Xianxialing and Wuyi Mountains; after extending into the border of Guangdong, this zone is called the Luofu,Jiulian and Qingyun Mountains (Fig.1). Their altitudes generally range between 1000m and 2000m above sea level, with a maximum altitude of 2158m at the Huanggang Mountain, the highest peak of the Wuyu Mountains. The “Zhejiang Fujian Mountainous Area”, with a mean altitude of about 1500m above sea level, is incapable of obstructing the inward intrusion of the Pacific derived moisture, and therefore both of the plain and hilly areas of Central China and the Zhejiang Fujian Mountainous Area belong to the same warm and humid subtropical climate zone, with flourishing herbs and forest, and favourable for the dwelling and multiplication of various kinds of aquatic and terrestrial animals. During the Early Cretaceous, the Zhejiang Fujian Area belonged to the active zones in the eastern coastal low land. In the early stage of Late Cretaceous, due to the westward subduction of the Pacific Plate, the Lishui Haifeng Fracture began to be activated. East of this fracture, the eastern part of the Zhejiang Fujian Guangdong provinces was rapidly elevated into the Coastal Mountains with the deposition of great thick bedded molasse accumulations formed during the process of elevation on the western slope and the piedmont belt, which are called the Fangyan Formation or the Hutoushan Conglomerate in Zhejiang; the Chishi Formation or the upper subgroup of the Shimaoshan Group in Fujian, and the Danxia Formation in northern Guangdong. All are composed of massive sandstone and conglomerate, ranging from several hundred meters to 1735m, with a maximum thickness possibly exceeding 2000m. After long standing weathering and denudation, the principle relicts are currently distributed in the Yongkang, Dongyang, Jin Qu, Ningbo, Xiakou and Si′an Basins of Zhejiang; the Shaxian, Shanghang, Chong′an and Hekou Basins of Fujian, and the Pingshi and Danxia Basins, together with those small basins around the Lianxian Yangshan area in Guangdong (Fig.2). In the small sized intermontane basins east of the Lishui Haifeng Fracture, there are neutral to acidic volcanic rocks intercalated with the conglomerate beds. These strata are called the Tangshang Formation in eastern Zhejiang, the upper subgroup of the Shimaoshan Group in Fujian. In eastern Guangdong, they are very likely corresponding to the pink rhyolite intercalated between the lower and upper red beds in the Xingning Basin. From the mudstone lenticulations intercalated in these great thick bedded sandy conglomerates, occasionally can be found fossil conchostracans, ostracodes, fishes, dinosaurs, sporopollen and plants of early Upper Cretaceous age, such as Linhaiella, Feiyunella, Yumenella, Paraclupea, Zhejiangopterus linhaiensis, Frenelopsis parceramosa, Pagiophyllum sp. and Cupressinocladus elegans and the sporpollen assemblage dominated by Schizaeoisporites with a small amount of angiospermous pollen. Based on the mean altitude of the modern Zhejiang Fujian Mountainous Area combined with the thickness of the denuded molasse accumulations, the Coastal Mountains of Southeast China ranged between 3500m and 4000m above sea level in altitude, with a width of about 500km from east to west. Such a huge barrier is much more than the modern Qinling Dabieshan Mountains, the geographical and climatic boundary between North and South China. This barrier completely blocks out the eastward Pacific derived moisture; as a result, the vast plain and hilly of the Yunmeng Lake water system in Central China began to become a tropic (subtropic) arid and hot semi desertized and sa
出处
《地层学杂志》
CSCD
北大核心
1997年第3期192-202,共11页
Journal of Stratigraphy
关键词
都江堰
侏罗系
地层对比
年代地层
地层
Coastal Mountains, SE China, desertization, saliniferous lakes, Upper Cretaceous.
