| Abstract：According to the strata of the blocks on both sides of the ancient Tanlu fault, it is concluded that the Bohai Sea
and its surrounding areas has a high-north, high-south, and low-middle paleotopography pattern in the Early Paleozoic,
where clear-water carbonate mainly deposited. Based on the observation of drilling cores, thin sections and outcrops,
typical sedimentary facies indicators are summarized. It is considered that there are three types of sedimentary facies in the
area, i.e. nearshore tidal flat facies, limited platform facies and open platform facies, five types of sedimentary subfacies
such as intra-platform depression, micrite mound, intra-platform shoal, lagoon, and platform flat, and nine types of
sedimentary microfacies. Based on the identification and fine correlation of sedimentary facies of Cambrian and
Ordovician, the lithofacies palaeogeography of four typical periods in the Bohai Sea and its surrounding areas is
reconstructed. Controlled by sea level rise and fall, tectonic subsidence, and paleotopography, coastal tidal flats developed
along paleouplifts and platforms developed widely in Lower Cambrian, oolitic shoals with large thickness developed in
Middle Cambrian, dolomite and lime flats developed from Upper Cambrian to Lower Ordovician, and micrite limestone
mainly developed in intra-platform depressions of open platform in Middle Ordovician. The results would be helpful to
the study of hydrocarbon genesis and reservoir formation in the Lower Paleozoic, which is a favorable target layer for
large or medium gas fields. |
