摘要
北京西郊下苇甸地区下寒武统昌平组底部含燧石角砾白云岩之上发育的一套豹斑灰岩,实为发育在高能环境下的凝块石灰岩,宏观形态上可包括斑状凝块石、带状凝块石和网状凝块石3种,其成因多与厚微生物席相关,且分别具有不同的微观结构。露头实测和镜下观察结果表明凝块石的初始沉积组分受控于沉积大/微环境,且三者的互动决定了凝块石的最终沉积特征。该套沉积成因的凝块石,其白云质凝块不局限于潜穴,且潜穴内部见大量保存完好微生物结构和疑似球状原生白云石,因此这种白云质凝块很可能与微生物白云石化密切相关,并以此区别于局限于生物遗迹位置,且内部充填物为粉细晶白云石的成岩成因的豹斑灰岩。
Developing above the chert breccia dolomites at the bottom of the Cambrian Changping Formation,Series 2,western Beijing,is a set of so-called leopard limestones that are actually thrombolites in a high-energy environment and macroscopically include spotted,zonary,and reticular thrombolites.With various microstructures,their geneses are always related to the thick microbial mat.According to the results of outcrop observation and thin section identification,initial fabrics are controlled by the sedimentary and microenvironment in the microbial mat,and their interactions result in the final characteristics of the thrombolites.Thrombolites derived from dolomitic clots of sedimentary origin are not restricted in burrows,where well-preserved microfabrics and primary dolomites are found,and are closely related to the microbial dolomitization.These phenomena show the difference between sedimentary throm-bolites and diagenetic leopard limestones whose leopard clots are limited to the location of the organic hieroglyph and filled with fine-grained dolomites.
作者
白莹
罗平
徐旺林
王珊
龚骥遥
BAI Ying;LUO Ping;XU WangLin;WANG Shan;GONG JiYao(Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China;No.2 Drilling Company of Bohai Drilling Engineering Company,CNPC,Langfang,Hebei 065007,China)
出处
《沉积学报》
CAS
CSCD
北大核心
2021年第4期873-885,共13页
Acta Sedimentologica Sinica
基金
国家科技重大专项(2016ZX05004)
中国石油天然气股份有限公司重大科技专项(2014E-3201)
中国石油勘探与生产分公司科技项目(Kt20180401)。
关键词
北京
寒武系
第二统
凝块石
豹斑灰岩
微生物席
Beijing
Cambrian
Series 2
thrombolites
leopard limestone
microbial mat
