川东北宣汉盘龙洞长兴组生物礁剖面沉积相分析

Analysis on sedimentary facies of Changxing Formation reefs profile of Panlongdong in Xuanhan,Northeastern Sichuan Basin

结合区域构造、地层概况、岩相古地理等方面的背景资料,对宣汉盘龙洞上二叠统长兴组生物礁地层剖面进行了观测描述。通过室内镜下岩石薄片鉴定分析,识别出主要岩石类型为礁灰岩、礁云岩、生屑灰岩、颗粒灰岩及晶粒白云岩。根据露头观察和室内镜下岩石薄片鉴定分析,结合岩石学、古生物等沉积相标志的研究,认为该剖面发育开阔台地、台地边缘生物礁和台地边缘浅滩三种沉积相类型,其中台地边缘生物礁发育,可进一步识别出礁基、礁核和礁前亚相,礁核以骨架礁和障积礁为主;台地边缘浅滩进一步划分为粒屑滩、鲕粒滩等亚相。初步总结出了该剖面的沉积相模式,并对该剖面的沉积演化序列和识别标志进行了讨论。

Based on the background information about the regional tectonics, stratigraphic profiles, paleogeographic, detailed description about reefs stratigraphic profile was made on the Upper Permian Changxing Formation. Meanwhile, combining with the rock slice appraisal analysis under the microscope indoor, main rock types were identified, such as limestone reef, dolomite reef, bioclastic limestone, granular limestone and dolomite. According to the outcrop observation, indoor rock slice identification analysis and the study of sedimentary facies marks through the perspective of petrology and paleontology, three types of sedimentary facies develop, there are open platform, platform margin reefs and platform edge shallow facies. In which, platform margin reefs is the most developed facies, and we could further identify the reef base, reef core and fore-reef subfacies. Reef core mainly consists of framework reef and barrier reef, and platform edge shoals facies could be further divided to grain beach and oolitic beach subfacies. Sedimentary facies pattern of this profile are sammarized preliminarily, and finally the sedimentary evolution sequence and their identification marks are discussed.