Molar-tooth构造(简称臼齿构造或MT)是前寒武纪碳酸盐岩中产出特殊的沉积构造,发育于特定的沉积环境。臼齿碳酸盐岩及其沉积环境的研究有助于其成因解释。大连金石滩新元古代兴民村组臼齿碳酸盐岩的研究表明,兴民村组的MT形成于开阔陆表海浅潮下带—潮间带动荡环境,海平面升降频繁;沉积序列主要为泥晶灰岩与含泥灰岩、砂屑灰岩与泥晶灰岩、纹层状泥晶灰岩与泥晶灰岩和砂屑灰岩与纹层状泥晶灰岩的韵律。MT形成于过饱和CaCO3的微高盐度和高古温度环境,少有陆源物质影响。
Molar-tooth structure(abbreviated MT)is a special sedimentary structure produced in carbonates of Precambrian,it was generated only in a certain sedimentary environment.A systematic study of MT-bearing carbonates and sedimentary environment will lend a hand in the genesis interpretation of MT structure.The study on Neoproterozoic MT carbonates from the Xingmincun Formation(Jinshitan,Dalian)revealed that this MT carbonates were formed in dynamic sedimentary environments changing from subtidal zone to intertidal zone of an open shallow sea with frequent fluctuation of sea level.The depositional succession of MT-bearing carbonates was characterized by the rhythm of micrite,muddy limestones and calcarenites.MT carbonates were precipitated from certain salinity and high temperature marine water of supersaturated CaCO3 receiving little influence from terrestrial material.