| The Ordovician is a set of relatively stable marine carbonate rocks deposition around Southern North China. Over the years many scholars have studied the area from all aspects in detail, and so a series of achievements were made in the oil and gas exploration in the Erdos Basin and adjacent areas. Although there are oil and gas shows in this area, but not yet obtains the significant breakthrough in the oil gas exploration. According to the theory of sedimentology, sequence stratigraphy and karst, this thesis carried on systematic study of Ordovician sequence stratigraphy in the Southern North China, on the basis of comprehensive analysis of the main section of the field measured, drilling core observation and logging data. The material manifestations of sequence bottom interface have 6 types:unconformity,palaeo-karst active surfaces,erosion surface,lithology and lithofacies conversion surface,overlap area,maximum flooding surface.The several types of sequence boundaries can be attributed to three kinds of genetic types. Uplift erosion unconformity interface sequence,transgression unconformity on the super sequence interface,land exposure unconformity interface sequence. On the basis of the identification of sequence interface,to divide Ordovician into nine third-order sequences(OSQ1-OSQ9) and three super sequence (SS1, SS2 and SS3).This paper analyse in detail the sequence stratigraphic units of the basic features, overlay and spatial distribution of the study area, and established Ordovician isochronous sequence stratigraphic framework。We also analyse the three sequence filling sequence development and structural response relationship. It reflects I-stage that SS1 is corresponding to OSQ1 and OSQ2,when the basin was uplifting violently and the unconformity of bottom surface was obvious. It was the process of compensated basin that the internal of basin was depositing more slowly than that it was settling. It reflectedⅢ-stage that SS3 is corresponding to OSQ8 and OSQ9,when the basin was uplifting more violently.Using supersequence system as a unit, we have compiled 4 maps of lithofacies palaeogeography of supersequence of Ordovician system, and revealed the characteristics and evolutions of lithofacies palaeogeography of strata succession of different system tracts. SS1 transgression of the rule in groups and the main deposition Yeli lower part of the formation, which is located in the north-east region of Wen County-Kaifeng-Shangqiu–Yongchen -Suzhou, are in neritic tidal environment. SS1 high deposition Liangjiashan group of the upper strata, which range of deposition is further back to the north than Yeli and limited to the north of the small area of Shangqiu-Yongchen–Suzhou, is in a restricted cloud platform flat environment. SS2 transgression of sedimentary Lower Majiagou Formation and the lower part of a ground launched Majiagou, located in the northeast region of Mianchi-Ru Chou - Huoqiu, mainly from tidal flat-restricted platform environments. SS2 high deposition launched Majiagou of the second and third formation, mainly in north of Dengfeng - Fuyang - Lingbi, where sedimentary environment is more limited, is in the tidal flat - restricted platform environments.Strong tectonic uplift provide favorable conditions for the development of Ordovician paleokarst in the Southern North China. Through observing field outcrop section, drilling core and the study of logging data, Ordovician paleokarst is shown as unconformity (weathering crust) eluvium, karst breccia, dissolution hole joint and other characteristic. They are mainly developed in the lower Ordovician and Ordovician top. Ordovician paleokarst is divided into three types as syngenetic period, supergene period and burial period karst. Different types of karst are obvious controled by different levels of sequence.Which the types of syngenetic period tidal flat, lagoon and uchinada are affected mainly by high-frequency cycles, and develop intragranular dissolved pore, mould pore and intergranular dissolved pore. Supergene period interlayer karstification obviously affected by the third-order sequence,it is the main factor in the formation of gypsum breccia. Burial period karst controlled by the second-order sequence,and develop organic corrosion secondary pore. Weathering crust karst's degree of development and distribution is the most widely,and it mainly controlled by the second-order sequence.This paper also discussed the impact and control factors of Ordovician karst, which tectonic, lithology, paleoclimate and paleogeomorphic are the main factors. In a comprehensive analysis based on multiple factors of the development of paleo karst, we adopted impression method to recover the paleogeomorphic Ordovician two weathering crust karst period.
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