Sedimentary Facies And Geochemical Features Of Wumishan Formation And Hongshuizhuang Formation In Jizhou,Tianjin

In order to clarify the sedimentary environment and paleoclimate of the Middle-Neoproterozoic in Jizhou,Tianjin,the author takes Wumishan Formation and Hongshuizhuang Formation of Jizhou,Tianjin as examples,combining the outcrop of the wild on the basis of the geological and sedimentary background of Yanliao Aulacogento carry out research on its geochemical characteristics.In the study area,the Wumishan Formation is in integrated contact with the Hongshuizhuang Formation,and the Wumishan Formation is in integrated contact with the underlying Yangzhuang Formation,and the Hongshuizhuang Formation is in integrated contact with the overlying Tieling Formation.Carbonate platform facies are widely developed in the Wumishan Formation,which is thick and stable with volcanic materials.The formation is dominated by magnesium-rich carbonate rocks with a small amount of clastic rocks and clay rocks.The carbonate rocks have obvious rhythms.There are a lot of stromatolites.The most basic sedimentary rhythm of the Wumishan Formation is from bottom to top: the bottom layer is the sandy argillaceous micrite dolomite in the upper part of the supra-tidal zone;the lower layer is the microcrystalline dolomite in the intertidal zone with laminar siliceous bands;the middle layer It is composed of thick layers of subtidal zone to massive sprite dolomite;the upper layer is intertidal zone with laminar siliceous strip microcrystalline dolomite;the top layer is supertidal zone with light-colored siliceous strip microcrystalline dolomite.The Hongshuizhuang Formation deposited a set of dark shale with a small distribution area and rich in organic matter,and a small area of dolomite was deposited in the early stage of the deposition due to the influence of the climate when the Wumishan Formation was deposited.The overall sedimentary environment is dominated by shelf sediments,the Hongshuizhuang Formation stromatolites are not developed,and algae plants are developed.The results show that:(1)The sedimentary facies of the Wumishan Formation and the Hongshuizhuang Formation are both carbonate platform facies.Among them,the Wumishan Formation is mainly a restricted platform facies,and the sedimentary rhythm of the supratidal zone-intertidal zone-subtidal zone is developed,and the Hongshuizhuang Formation is mainly shelf facies.(2)Carbonate rocks are developed in Wumishan Formation.The chemical composition of the samples is mainly CaO and MgO,and their contents are similar.More SiO2 content indicates that carbonate rocks were mixed with more terrestrial debris during the deposition period;Mudstone and shale are developed in Hongshuizhuang Formation,and the chemical composition of the sample is mainly SiO2.(3)The magnesium-aluminum ratio(m value is 8-21670)shows that the depositional environment of the Wumishan Formation and the Hongshuizhuang Formation is a lagoon carbonate sedimentary environment.The lower m value(8-12)in the Hongshuizhuang Formation indicates that there were Fresh water is injected.(4)The Mn content and Na/Al show that the climate during the deposition of the Wumishan Formation was arid,and it had the characteristics of frequent transitions between arid and short-term humid climates.The climate during the deposition of the Hongkongzhuang Formation was warm and humid.