摘要
结合野外露头剖面观察与深入剖析,对宣汉盘龙洞长兴组生物礁沉积特征和成礁模式进行了室内综合分析。该礁位于鄂西-城口海槽西侧台缘带,为相对海平面整体下降背景下形成的一套加积-进积型台地边缘生物礁。该露头出露良好,长兴组以海绵骨架礁灰岩和海绵骨架礁白云岩为主。综合岩性、古生物等沉积相标志,该区长兴组属于碳酸盐岩台地边缘沉积体系,可进一步划分出斜坡相、台地边缘生物礁和台地边缘生屑滩相,其中台地边缘生物礁又可划分为礁基、礁核、礁盖、礁前、礁后等亚相。区域沉积环境、岩性、古生物以及生物礁的内部构成分析认为,盘龙洞生物礁可分为3期成礁旋回:第一旋回礁是低能环境下形成的未经充分生长而被淹死的礁,主要由生屑泥晶灰岩和少量骨架岩组成;第二旋回礁形成于较高能环境下,经历了充分生长后暴露而死亡,暴露时间短,仅顶部发生了较弱的白云岩化;第三旋回礁则形成于高能环境下,经历了充分生长并暴露出海平面后死亡,其死亡后经波浪和水流的改造作用而形成生屑滩,长期暴露发生强烈白云岩化。
Based on the multidisciplinary analysis of outcrop and microfacies observation,the sedimentary characteristics and forming model of Changxing Formation reef are researched in detail in Panlongdong Section.The reef is located in the platform margin of Exi-Chengkou trough.It is a huge platform marginal reef deposition during aggradation-progradation in a background of relative sea-level fall.The reef is full of outcrops.Sponge skeleton reef limestone and sponge skeleton reef dolomite are the main rocks.According to the sedimentary facies＇ characteristics,Panlongdong region belongs to a carbonate platform marginal sedimentary system,and can be divided into slope facies,platform marginalreef,and platform marginal bio-clast bank.The platform marginal reef facies can be divided into reef base,reef core,reef cap,fore reef,and back reef.Panlongdong reef consists of three depositional cycles：the first cycle of reef was formed in a low energy environment which was drown without sufficient growth;the second cycle of reef was formed in a relative high energy environment which died of exposure after experiencing sufficient growth with weak dolomitization on the top;and the third cycle of reef was formed in a high energy environment which died of exposure after experiencing sufficient growth,and then the reef formed a bio-clast bank,and later was destroyed by waves and tides.The reef and bio-clast bank experienced an intensive dolomitization after a long-term exposure.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2015年第5期1322-1331,共10页
Journal of Jilin University：Earth Science Edition
基金
国家油气重大专项(2011ZX05004)
中石油重大专项(2014E-3201)
关键词
长兴组
生物礁
沉积特征
成礁模式
Changxing Formation
reefs
sedimentary characteristics
reef-forming model
作者简介
李秋芬（1979-），女，博士，主要从事沉积地质学、层序地层学研究，E-mail：liqiufen@petro—china．com．cn。
