辽东大连新元古代臼齿构造（Molar-tooth）形态与沉积微环境关系探讨

臼齿构造（Molar tooth），简称MT，是一种仅发育于前寒武纪碳酸盐岩地层中的特殊沉积现象。在全世界的许多地区
广泛发育。中国辽宁大连地区新元古代碳酸盐岩中发育了大量的臼齿构造。野外和室内的观察研究将MT 形态划分为2 大类
（原地MT 和异地MT），5 亚类（条带状、杆状、蠕虫状、斑状和碎屑状），主要发育浅潮下带-潮间带环境。通过对MT 形
态及发育的微环境特征分析得出，大连地区MT 形态与沉积微环境存在一定的对应关系。泻湖中以MT1-1 和MT1-2 类型为主，
潮间带中部主要发育MT1-3 和MT4 类型，潮间带中部-潮间带上部常见MT2 和MT3类型，浅潮下带风暴浪基面附近或潮间
带下部高能环境多见MT5 类型。由此推断，在水体安静并且陆源碎屑物质干扰小的环境中，容易产生平直或弯曲的宽、长
条带状MT，而在动荡的水体中或是陆源碎屑物质含量高的环境中，往往形成短小的MT。因此，MT 的形态类型一定程度受
到沉积水动力条件和陆源碎屑物质混入的影响。此外，大量的陆源碎屑物质的混入或抑制MT形成或减小MT 的发育规模。

Relationship Between Depositional Environment and Morphology of Molar Tooth:Taking the Neoproterozoic Molar-tooth in Dalian,China as an Example

Molar Tooth(MT),is a special sedimentary phenomenon and only developed in carbonates in Precambrian.It has been found in many areas of the world.Abundant MTs with complicated morphology were found in the Neoproterozoic carbonate rocks of Dalian,Liaoning Province,China.The MT from Dalian was divided into autochthonous MT and allochthonous MT,according to its morphology.The autochthonous MT was further divided into four subtypes containing ribbons,bars,worms,spots and the allochthonous MT consists of fragments only.The MTs from Dalian were mainly developed in a shallow subtidal to intertidal zone.Based on the analysis of different types of MT and their distribution in a micro-sedimentary environment zone,a special relationship between morphology and micro-sedimentary environment was found.MT1-1 and MT1-2 types mainly occur in a lagoon;MT1-3 and MT4 are the principal types in the middle of a tidal zone;MT2 and MT3 dominate the middle to upper pare of a tidal zone,while MT5 type appears in a shallow subtidal zone(around base of storm waves) or lower of an intertidal zone.Therefore we infer that wide and long MT ribbons were probably easily produced in a low-energy environment without substance from land,but a high energy environment with plenty of land-substances is favorable for short and small MT.It is concluded that hydrodynamic force and land-substances can influence the morphology of MT.Besides,considerable land-substances can inhibit the formation of micro-spars or reduce the sizes of MT.