广西江平地区沙坝-泻湖沉积相序与沉积环境演变过程

Sedimentary Facies Sequences and Evolutionary Process of Sedimentary Environment of the Barrier-lagoons in Jiangping area, Guangxi

本文在地貌、第四纪地质野外调查和３３个钻孔资料的基础上，运用粒度、碎屑重矿物、微体古生物和１４Ｃ年代测定等方法探讨江平沿岸沙坝－泻湖体系的沉积相序和沉积环境演变过程。沙坝－泻湖发育在一片起伏不平的基岩侵蚀面上，其沉积相序自下而上为：基岩侵蚀面→河床→、河漫滩相→河口湾、近岸浅海相→滨外沙坝、半封闭泻湖相→风成沙丘、封闭充填泻湖沼泽相。本区的沙坝泻湖属于海退型。作者初步认为本区沙坝可分为新、老２期，老沙坝大约形成于６７００～３６００ａＢ．Ｐ，新沙坝大约形成于２３００～１０００ａＢ．Ｐ。

On the basis of the landform and the field investigation of the Quaternary geology and thedata of 33 drilling bores, thiss paper discusses sedimentary facies sequences and evolutionaryprocess of sedimentary environment of the barrier-lagoons in Jiangping area, Guangxi, accord-ing to size of grains, heavy minerals, micropaleontologic analyses and 14 C dating. The barrierlagoons develop on the uneven erosional surface of basement rock. From bottom to top, the sedimentary sequences are erosional surface of basement rock river bed,flood land factesestuary,off shore factes offshore bars,Semi-enclosed lagoon facies wind-borne dunes, closed filling lagoon facies. The barrier-lagoons belong to marine regression type. The authors preliminarily consider that these barriers can be divided into two ages: the new age and the old age. Oldbarriers were formed about 6 700~3600 a B. P., and the new barriers were formed about2300~1000 a B. P..