宏观藻类化石及其相关的“前寒武纪谜”:对天津蓟县剖面中元古代早期高于庄组第三段中一些现象的思考  

Brief Introduction on Megafossil of Algae and Relative Precambrian Enigmas: Ponder on Some Phenomena from the Third Member of Gaoyuzhuang Formation of the Early Mesoproterozoic at the Jixian Section

作　　者：梅冥相[1,2] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《现代地质》2009年第4期616-624,共9页Geoscience

基　　金：国家自然科学基金项目(40472065)

摘　　要：在漫长的前寒武纪,存在若干谜一样的问题,如叠层石的生长机理、臼齿状构造的成因、白云岩的形成机制和宏观藻类化石的生物学属性及其分类归属等。宏观藻类化石是指那些肉眼可见的低等植物化石,因为与现代藻类的亲缘关系尚未完全确定,它们的生物学属性及其分类位置还存在较多的争议,所以宏观藻类化石成为一个"前寒武纪谜"。发现于天津蓟县剖面高于庄组第三段非叠层石灰岩(均一石灰岩)中的可能的实体宏观藻类化石,与成因还存在争议的臼齿状构造共生,包括球状丘尔藻、椭球状寿县藻、带状塔乌藻和豆荚状荚藻等4种类型,尤其以前两种居多,组成一个丘尔藻-寿县藻组合;这些多为球状体的化石,曾经被认为是臼齿状构造的一种,称为"球状臼齿状构造",但是,由于这些宏观藻类化石具有规则的形态、较为明显的可能的细胞显微结构,与充填臼齿状构造的方解石微亮晶形成明显的区别,不属于臼齿状构造;而且以实体化石产出,与多年来所描述的碳质压型化石又存在较大的区别;同时,该球状化石的中心部位硅化而边部为钙化体,也明显区别于一般的钙质结核、燧石结核、凝灰岩结核和气泡构造等。这些球状实体化石,要比H.J.Hofmann所报道的加拿大麦肯齐山小达尔群(Little Dal Group)的臼齿状构造灰岩中的实体宏观藻类化石的形成时代要老得多,有可能是最为古老的实体宏观藻类化石。高于庄组臼齿状构造灰岩中的实体宏观藻类化石,成为思考若干前寒武纪谜的重要现象。In the long Precambrian,there are several problems like the enigmas such as the growth mechanism of stromatolites,the origin of molar-tooth structures,the forming mechanism of dolomites and the biological ascription of algae megafossils.Megascopic algae are also nominated as the cell-prothalli plant.Both the megascopic algae and the cell-prothalli plant are the temporary-pseudo denomination.Thus,studies on the algae megafossils are very important for the research on the origin and the systematic evolution of the metaphyte as well for stratigraphic correlation of the Precambrian strata.Algae megafossils refer to those fossils of the low-grade plant that can be seen by the naked eyes.Because of the absence of modern analogy,the confirming of the biological classified location and attribution of megascopic algae of the Precambrian is very difficult and is highly contentious,which results in a Precambrian enigma.Algae megafossils in beds of the leiolite limestones of the third member of Mesoproterozoic Gaoyuzhuang Formation at the Jixian section are particularly characterized by the three-dimensional fossils and are frequently parageneic with the molar-tooth structures whose origin is also highly contentious.These three-dimensional fossils can be grouped into several genuses,i.e.the spheroidal or sub-spheoidal category of the Genus Chuaria,the ellipsoidal category of the Genus Shouhsienia,the beanpod-shaped category of the Genus Phascolites and the ribbon-or vein-shaped category of the Genus Tawuia,and all of them make up an assemblage of the Chuaria-Shouhsienia.These algae megafossils can still interpret the sprereoidal molar-tooth structure.Several features of algae megafossils,such as the older forming duration that is more than 1,500 Ma,the paragenesis with the molar-tooth structure,the regular shape of three-dimensional fossils and the possibly celluar microstructure,show a strong difference from both microspars filling the molar-tooth cracks and carbonaceous compression.Thus,these megafossils of algae are not t

关 键 词：实体化石 细胞显微结构 宏观藻类化石 前寒武纪谜 

分 类 号：P534.1[天文地球—古生物学与地层学] Q911.6[天文地球—地质学]