辽宁兴城夹山地区中元古界团山子组叠层石的发现及其地层学意义

摘要

Stromatolites from the Mesoproterozoic Changcheng System dolomite in the Jiashan area of Xingcheng are reported for the first time. The stromatolite bed had previously been attributed to the top of the Changzhougou Formation. From the bottom up, the stromatolites occur in the section as Stratifera sp. , Cryptozo-on sp. , Eucapsiphora sp.. Both this stromatolite assemblage and those from the Tuanshanzi Formation in adjacent area of Huludao belong to the type of stromatolite zones in the Tuanshanzi Formation in Yanshan and Taihang Ranges. The presence of the stromatolites in the section provides important biostratigraphic evidences to conclude that the beds belong to the Tuanshanzi Formation. According to the lithostratigraphic characteristics, and the relationship between the vertical distribution rule of stromatolites' morphology and the paleoenvironment, the sedimentary environment history of the Tuanshanzi Formation in Xingcheng area should be fromregression (shallows to intertidal zone and supratidal zone) to transgression (intertidal zone and supratidal zone to intertidal zone and subtidal zone).%辽宁省兴城市夹山地区中元古界长城系白云岩中首次发现叠层石,其产出层位为前人在这一地区划分的“常州沟组”顶部,自下而上为Stratifera sp.层叠层石(未定种),Cryptozoon sp.卷心菜叠层石(未定种),Eucapsiphora sp.叠球藻叠层石(未定种).该组合以及邻区葫芦岛等地团山子组中的叠层石类型均属于燕山、太行地区团山子组叠层石组合带分子.上述叠层石的发现为夹山地区划分出团山子组提供了重要的生物地层学证据.根据岩石组合特征、叠层石形态垂向分布规律及其与古环境演化的关系分析,认为兴城地区团山子组沉积环境演化为海退沉积序列(浅滩到潮间、潮上带)到海侵沉积序列(潮间、潮上带到潮间、潮下带).