During Early Paleozoic the North China platform experienced two marine transgression-regression supercycles. The supercycle A represents a time span from Cambrian through early Arenigian of Early Ordovician. The Xinji age(equivalent to the Canglangpu age in the Chinese regional stratigraphic standard)through Xuzhuang age(Early Cambrian through early Middle Cambrian)features a general sea-level rise during which marine transgression generally followed a south to north direction; the Zhangxia through Gushan ages represent a persistent high sea-level period; from then on began a gradual regressive phase(middle Upper Cambrian through early Arenigian), till the end of which the North China platform(except for the northernmost part)was basically exposed. The supercycle B represents a time span from late Arenigian to early Caradocian. In the supercycle A, marine transgression and regression cycles often lead to frequent flooding and exposure of the nearshore areas of the platform. In contrast, in the supercycle B secondary sea-level rise and fall cycles did not result in distinct flooding and exposure of the nearshore areas, instead, the sea-level falls on the platform often produced lagoonal environments with widely distributed evaporite deposits. The Yeli and Liangjiashan Formations(Tremadocian Early Arenigian)of the North China platform are composed of two sequences. The "Yeli" sequence contains the Yeli Formation and basal part of the Liangjiashan Formation, which corresponds to conodont Utahconus beimadaoensisMonocostodus sevierensis Zone through Scalpellodus tersus Zone. The “Liangjiashan” sequence comprises the rest of the Liangjiashan Formation, which corresponds to conodont Serratognathus bilobatus Zone through Paraserratognathus paltodiformis Zone. Because of southwestward marine transgression from the northeast, the northern part of the platform is characterized by the transgressive system tracts and highstand system tracts, basically consisting of open marine deposits, whereas the southern and western parts mainly consist of highstand system tracts indicated by tidal flat and restricted marine deposits, between which such as in the Quyang Wutai area, the sequence is composed of shoal deposits. The above system tracts distribution pattern is coincident with the biostratigraphic zones of previous workers. Biozones of the transgressive interval are missing in the southern Shanxi and northern Henan region. In addition, late or latest highstand deposits are absent in the southern part due to northward regression from the south. At the northernmost part including Pingquan and Qinhuangdao of Hebei Province there still occurs a stratigraphic interval(Jumudontus ganandaScolopodus sunanensis Zone)which is missing in other parts at the top of the Liangjiashan Formation. This interval probably represents the lowstand deposits of the following sequence. The Jiawang Formation in the south should be correlated with the lower-middle part of the Lower Majiagou Formation in the north, instead of the base.
Ma Xueping,Han Zuozhen,Wang Yinghua. THE TREMADOCIAN-EARLY ARENIGIAN(EARLY ORDOVICIAN)SEQUENCE STRATIGRAPHY AND LITHOFACIES PALEOGEOGRAPHY OF NORTH CHINA[J]. Chinese Journal of Geology, 1998, (2): 166-179.