Abstract：Carbonate rocks are the important buried-hill oil and gas reservoirs in the Lower Paleozoic in Jizhong Depression. The researches show that the Ordovician developed on a typical epicontinental platform with four sedimentary subfacies including supratidal zone,intertidal zone,restricted subtidal and open subtidal zone,while it was further divided into 11 sedimentary microfacies,such as muddy-dolomitic flat,gypseous-dolomitic flat,dolomitic flat and dolomite-dominated lagoon etc. It is constructed with four third-order sequences(SQ1~SQ4),while sequence-4 only developed transgressive systems tract. The Yeli stage(SQ1-TST)which belonged the first Ordovician transgressive period developed open subtidal-intertidal-supratidal subfacies from north to south,while the Liangjiashan stage(SQ1-HST)mainly developed intertidal subfacies with locally distributed supratidal subfacies. The early Majiagou stage and late late Majiagou stage which were the second and third transgression mainly developed restricted subtidal flat and open subtidal flat,while bioclastic shoal and gravel shoal were locally developed. The early late Majiagou stage(SQ2-HST)and the early Fengfeng stage(SQ3-HST)were dominated by intertidal and supratidal subfacies,which were stable depositions of dolomites. The fourth transgression systems tracts were recorded in the late Fengfeng stage(SQ4-TST),which mainly developed open subtidal subfacie,and intertidal flat microfacies and dolomitic flat sporadically developed in the northern of Jizhong Depression. Due to the Caledonian tectonic movement,the North China Platform was uplifted as a whole,and the top of the Ordovician in the Jizhong Depression was eroded until the Carboniferous.
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