摘要
寒武纪苗岭世早期的毛庄组沉积时期,华北地台围绕着西北部的古陆分布着两个沉积相带,靠近古陆的是局限潮坪相带,远离古陆的是开阔潮坪相带,前者以海侵体系域的干旱红层或海岸萨布哈沉积与高水位体系域的潮坪相白云岩沉积序列为特征,后者则以海侵体系域的潮坪相砂泥岩与开阔海台地相(潮下坪)灰岩沉积序列为特征;大连金州湾剖面的毛庄组,属于远离古陆的开阔潮坪相带的产物,在其高水位体系域中为一套夹有鲕粒灰岩的叠层石与均一石生物丘灰岩,组成一个特别的生物丘复合体。以下特征表明,这个微生物碳酸盐岩生物丘复合体代表着一个较为罕见的蓝细菌主导的微生物席形成的微生物碳酸盐岩的典型实例:①在生物丘复合体第一个单元的大型柱状和穹隆状砂泥质叠层石中发现孢网菌状组构,说明了这些叠层石属于蓝细菌微生物席的钙化作用产物;②在第二个单元均一石灰岩生物丘中,见到少量丝状蓝细菌鞘化石,表明均一石可能为较厚的蓝细菌微生物席的钙化作用产物;③在小型柱状叠层石组成的顶部单元中,保存较好的蓝细菌泥晶纹层、以及充填在叠层石柱体之间的基质中的蓝细菌团块,较为特征地说明了这些小型柱状叠层石是蓝细菌所主导的微生物席的建造物;④在鲕粒灰岩组成的第三个单元中,鲕粒边缘中的丝状蓝细菌鞘化石,表明了鲕粒的蓝细菌生物膜成因。因此,毛庄组生物丘复合体构成了一个壮观的沉积学现象,成为窥视"显生宙早期第一幕蓝细菌钙化作用事件"的典型实例。
The depositional period of the Maozhuang Formation of the early period of the Series 3 of the Cambrian in North-China Platform was distributed in two facies zones around the oldland,i.e.the restricted tidal-flat facies zone near the oldland and the open tidal-flat facies zone off the oladland.The restricted tidal-flat facies zone is marked by the transgressive purple and red mudstone of the arid red bed(or sebkha facies)and the high-stand dolostone of the clear tidal-flat facies.The open tidal-flat facies zone is characterized the transgressive purple sandy mudstone of the tidal-flat facies and the high-stand limestone of the subtidal facies.The Maozhuang Formation at the Jinzhouwan section in the Dalian City of Liaoning province is composed of an open tidal-flat facies,the high-stand limestone which is marked by a set of bioherm limestones of both the stromatolite and the leiolite interbedded oolitic grainstones,which make up aparticular bioherm complex.Several features of this particular complex of bioherm indicate that it is a rare and typical example of microbial carbonates dominated by the cyanobacterial mat:①In the first unit of the complex of bioherm madding up of large column and domelike silty and muddy stromatolites,the bacinellid fabric indicates that these stromatolites resulted from the calcification of cyanobacterial mats;②Within the second unit composed of leolites,few sheath fossils of filament cyanobacteria indicate that the formation of leolites is genetically related to the calcification of the relatively thick cyanobacterial mat;③In the top unit composed of small column like stromatolites,both the sheath fossils of filament cyanobacteria within the stromatolitic columns and the micritic clump composed of cyanobacteria clearly show that these stromatolites were constructed by the microbial mat dominated by cyanobacteria;④In the third unit,sheath fossils of filament cyanobacteria developed in margin of a ooid indicate that the origin of these ooids is genetically related to the cyanobacterial biofilm.Therefore,this bioherm complex in the upper part of the Maozhuang Formation represents an impressive sedimentological phenomenon and is a typical example for studying the first episode of the cyanobacterial calcification event in the early period of the Phanerozoic Eon.
作者
梅冥相
胡媛
孟庆芬
MEI Mingxiang;HU Yuan;MENG Qingfen(School of Earth Sciences and Natural Resources,China University of Geosciences,Beijing,100083;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing,100083)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2020年第2期375-395,共21页
Acta Geologica Sinica
基金
国家自然科学基金会资助项目(41472090,40472065,49802012)的研究成果.
关键词
钙化蓝细菌
微生物碳酸盐生物丘
毛庄组
寒武系
大连金州湾剖面
Calcified cyanobacteria
bioherm complex of microbial carbonate
Maozhuang Formation
Cambrian
Jinzhouwan section of Dalian City
作者简介
梅冥相,男,1965生,教授,主要从事沉积学与地层学研究工作,Email:meimingxiang@263.net。
