摘要
华北奥陶系的研究,从刘季辰等(1919)在徐州贾汪进行地质调查,及孙云铸等(1922)在唐山建立标准剖面起,至今约有60年。以往的研究,主要限于地层和古生物方面,岩石学的研究,只是近来才逐渐开展起来。
Basing upon the petrographic studies of Ordovieian carbonate rocks in Quyang region,Hebei province,the sedimentary properties of the wide-spread tidal flat with evaporatic carbonate in North China platform are discussed in this paper.The Ordovieian series found in Quyang region is entirely made up of carbonate rocks and can be divided into ten main types of carbonate lithofacies.In supratidal zones there are breeciated dolomite,gypsum-bearing dolomite,laminated dolomite and stromatolitic dolomite.Mudcracks,desiccation cracks,bird’s eye and gypsum are widly developed in these dolomites.The brecaiated dolomite is composed of fragments of mudcrack;In the intertidal zones there are micrite,wormkalk,pelmicrite,biomicrite and the incomplete mudcracks-(deformed usually by weathering),desiccation cracks,solution mottles and burrows as well.It is found that the formation of"mottles"was a result of selective replacement of sedimentary-diagenetic fabrics by dolomite.In subtidal low-energy zones there are pelmicrite,biomicrite and bio-intraclast micrite.Here,the biodetritus are aboundant,while the dolomitezation is rather weak.Finally,in subtidal high-energy zones there are biosparite,and biointrasparite which occurred in the form of isolated and irregular small beaches under favorable,conditions.The contents of trace elements are different for different lithofacies,for instance,the content of Sr reaches the maximum in the subtidal zone,whereas the contents of Ti,Zr,Ni and Ba are highest in the supertidal zone.The Ordovieian carbonate rocks of Quyang region distinctly exhibit of cyclic and rhythmic features in vertical section.As far as we know,there are two categories of rhythm with five typical rhythms that differ from each other in both distribution and constitution.
作者
王尧
潘正甫
Wang Yao;Pan Zhengpu
出处
《地质科学》
1980年第3期218-230,301,共14页
Chinese Journal of Geology(Scientia Geologica Sinica)
