Growth mechanism of stromatolites in the Ganjingzi Formation,Sinian System,in Liaodong Penisula
Objectives:The stromatolites in Ganjingzi Formation,Sinian System(Ediacaaran System),in Liaodong Penisula,are ideal object for studying the construction of Neoproterozoic microbial carbonate,which is of great significance for restoring paleoenvironment and paleoecology.Methods:Based on field investigation on the Yuanjiagou profile,Fuzhou Bay,Liaodong Penisula,the position of the outlying stromatolites in the Ganjingzi Formation,the macroscopic morphological characteristics of stromatolites,and the morphological changes of stromatolite columns and lamellar structures are identified and recorded.Through the observation of the laminae,the different growth stages of the laminae are distinguished,and the influence of the environment on the bifurcation and morphology of the stromatolite columns are analyzed.The stromatolites building process and characteristics of Neoproterozoic the Ganjingzi Formation stromatolites are reconstructed by comparing them with modern stromatolites.After comprehensive discussion,the growth mechanism of the Ganjingzi Formation stromatolites is summarized.Results:Based on different lithology,the Ganjingzi Formation is divided into three sections from bottom to top in the Yuanjiagou profile,Fuzhou Bay,Liaodong Penisula.Stromatolites appear at the bottom of the Lower Member and the top of the Upper Member of the Ganjingzi Formation.The stromatolites at the bottom produce stromatolite mound or the large-scale stromatolite biostrome at the top.The stromatolites colonize the hard substrate and grow perpendicular to the substrate at the beginning stage.Under the influence of hydrodynamic conditions and photosynthesis,stromatolites gradually grow vertically upward.The stromatolites in the stromatolite mound present a pattern combination of corrugate—columnar—cumulus,and the stromatolites in the stromatolite biostrome present a pattern combination of corrugate—columnar—long columnar,both of which reflect the changing trend of stromatolite morphology with increasing water depth.A comprehensive comparison of modern stromatolites shows that the microstructure of the Ganjingzi Formation stromatolites is similar to that of modern stromatolites,and growth and branch have certain comparability.Conclusions:The stromatolite laminae of the Ganjingzi Formation show different sequences of formation of light laminae and dark laminae.The morphological characteristics of stromatolites show that the growth and branched of stromatolites are affected by the environment to some extent.The formation of stromatolites is subject to environmental changes.The extensive growth of stromatolites requires ample space and a suitable environment.The presence of hard substrates creates favorable conditions for the growth of stromatolites.From micro to macro,the influence of biological factors on the growth and building characteristics of microbial mats gradually increased,while the influence of environmental factors gradually decreased.
万方数据
维普
