浙江江山晚古生代岩相古地理及其构造控制

LATE PALAEOZOIC SEDIMENTARY FACIES AND PALAEOGEOGRAPHY AND THEIR TECTONIC CONTROLS IN JIANGSHAN, ZHEJIANG

关键词:  古生态学  沉积序列  华夏古陆  沉积环境  构造控制

Key words:  palaeoecology  sedimentary Sequence  Cathaysia  sedimentary environment  tectonic control

摘要:

根据岩石学、古生态学、地球化学特征及沉积序列,结合区域地质资料的系统研究,本文论述了浙江江山地区石炭纪和二叠纪沉积相与沉积环境的演变规律及其构造意义。
叶家塘组属辫状河流快速堆积的产物,区域上为早石炭世大塘期华夏古陆西缘冲积相带的组成部分;藕塘底组具海陆交互沉积特征,剖面结构为岸进序列;石头山灰岩为浅海碳酸盐台地稳定沉积;丁家山组是浙西台地发展过程中浑水干扰叠加的产物。
研究表明,华夏古陆在晚石炭世威宁期和早二叠世茅口期发生过差异性隆起,威宁期隆升造成藕塘底组的岸进序列。茅口期隆升提供泥砂浑求,浙皖海盆碳酸盐台地的发育受到干扰。由此可见,古陆间歇性活跃、海浸持续稳定是本区华力西期构造发展的基本特点。

Abstract:

In the light of petrographic, palaeoecological and geochemical characteristics and sedimentary sequences, in combination with regional geological data, the present paper deals with the evolution and tectonic implications of the Carboniferous and Permian sedimentary facies and environments in the Jiangshan region, Zhejiang.
The Yejiatang Formation is interpreted as the rapidly accumulated products in braided rivers, and regionally,as a part of the Datangian (Early Carboniferous)alluvial facies belts on the western margin of the Cathaysia. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with progradational sequences. The Shitoushan Limestones are assigned to the stable deposits on shallow-marine carbonate platforms. The Dingjiashan Formation is thought to be the turbid-water-disturbed and superimposed products during the western Zhejiang platform development.
During the Weiningian(Late Carboniferous)and Maokouian (Early Permian),the differential uplifts once occurred on the Cathaysia. The Weiningian uplifts were responsible for the formation of the progradarional sequences in the Outangdi Formation,whereas the Maokouian uplifts delivered to the turbid water with mud and sand,which permitted the development of the carbonate platforms in the Zhejiang-Anhui marine basin to be disturbed. It follows that the Variscan tectonic development is characterized by the intermittently active ancient land and steady transgressions in the study area.