Paleoecology of the Ordovician Reef-Shoal Depositional System in the Yijianfang Outcrop of the Bachu Area,West Tarim Basin  

作　　者：焦养泉 吴立群 荣辉 王永标 王瑞 

机构地区：[1]Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences [2]Faculty of Earth Resources,China University of Geosciences [3]Faculty of Earth Sciences,China University of Geosciences [4]College of Geosciences,China University of Petroleum

出　　处：《Journal of Earth Science》2012年第4期408-420,共13页地球科学学刊（英文版）

基　　金：supported by the SINOPEC Forward Looking Project of China (No. YPH08114)

摘　　要：The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang （一间房） outcrop of the Bachn （巴楚） uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system： an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies （a reef base, a reef core, and fore-reef breccias）; the organic shoal is formed from five types of genetic facies （tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals）. The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The calathium, archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while weil-preserved girvanella and nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals.The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang （一间房） outcrop of the Bachn （巴楚） uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system： an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies （a reef base, a reef core, and fore-reef breccias）; the organic shoal is formed from five types of genetic facies （tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals）. The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The calathium, archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while weil-preserved girvanella and nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals.

关 键 词：PALEOECOLOGY reef-shoal depositional system ORDOVICIAN Tarim basin. 

分 类 号：P618.13[天文地球—矿床学]