摘要
本文首次报道了天津蓟县中元古宇雾迷山组核形石的演化系列,依据雾迷山组的相序,辨释了它纵向序列的旋(韵)律沉积特征,进而筛析了此中核形石的成生.发育全过程,遂得以认出核形石的雏形——弥散粒.从核形石发育的各个时期看,其生成环境,特别是水动力势态.有着不同强度的能量.
Wumishan Formation of middle Proterozoic in Jixian county, Tianjin, mainly consist of bio-dolostone, about 3000m in thickness. As the results of field section survey, microscopic analysis of thin sections and electronmicroocopic scanner of rock deperis, the whole process of development and evolution of oncolite is recognized. The dispersal grain is the embryonic form of oncolite, its different pattern and character of coat reflect various occurence in the early stage of coated grain. If we regard the whole process of growth from initial dispersal grains to resultant product of oncolite as a series of processes, its growth envi-ronment is not confined to conventional recognization-sedimentary medium is a shaking and low-energy state.
Vertical sequence of Wumishan Formation show spiral-rhythm accumlation and within each sequence algal coat from dispersal grain to oncolite also display synchronous evolution rhythm. Diameter of grams varies from 0.5-2mm to 10-20mm. Periodical and sprial evolution series of algal coat arc from simple to com plex.
Macroscopically, disperal grains are black-brown spherical grains, containing much organic materials. They float and disperse in the dolostone. Under polarization microsoope. they are radiation concentric, winkle pisolit and flat leaf. Under electronic microscope, a flower is formed by a few slices of dolostone gathered together, with diameter of several to tens of μm.
出处
《沉积学报》
CAS
CSCD
北大核心
1992年第2期19-27,共9页
Acta Sedimentologica Sinica
