浙江江山晚奥陶世浊积岩系特征及浙西浊积扇模式的探讨

CHARACTERISTICS OF THE LATE ORDOVICIAN TURBIDITE SERIES IN JIANGSHAN,ZHEJIANG WITH DISCUSSION ON THE WEST ZHEJIANG TURBIDITE FAN MODEL

摘要:

在扬子地台东南的浙西、皖南地区,晚奥陶世晚期地层具有鲜明的沉积学特征。它对认识本区加里东晚期古构造环境有着十分重要的意义。关尹文(1959)、李继亮(1978)、吕洪波(1987)、余素玉(1986)先后在临安、宁国、绩溪等地对其韵律结构、沉积构造及矿物岩石学方面进行了不同程度的研究。关尹文、吕洪波称之为浅水复理石。李继亮认为是深水浊流沉积。笔者(1989)在江山一带对相应地层进行了系统的沉积相研究,结合浙、皖浊积岩系特征的对比,对浊积扇的构成及其发育的构造古地理条件进行了初步探讨。

Abstract:

It is suggested that the late Late Ordovician Changwu Formation in Jiangshan, Zhejiang are composed mainly of the tidal flat deposits and turbidity current deposits in terms of sedimentary sequences and environmental indicators. During the Late Ordovician, there occurred three turbidity current events in western Zhejiang, the second of which had the maximum energy and most important influences. On the basis of the regional geological data from western Zhejiang and southern Anhui, in conjunction with the study of sedimentary systems in the Zhejiang-Anhui marine basin, the sedimentary environments in the study area may be divided into four types, i.e. tidal flat, organic reefs, continental shelf and deep-water basin. Meanwhile, the regional correlations have also been made for the turbidite series there. A model for the development of the West Zhejing turbidite fan is proposed according to the Bouma sequence, grain size, sedimentary structures and palaeocurrent data. The present paper further deals with three tectonic factors controlling the development of the turbidity current deposits, i.e. left-lateral shear-tension movement of three deep faults controlling the Zhejiang-Anhui marine basin, the uplift of the Cathaysia and differential subsidence of the Zhejiang-Anhui marine basin. This has provided a useful tool for interpreting tectonics and palaeogeography of the Cathaysia from Phanerozoic time onwards.