FORMATION AND EVOLUTION OF THE EARLY PALAEOZOIC SHALLOW MARINE CARBONATE PLATFORM IN THE HEBEI-WESTERN SHANDONG AREA

During the Early Palaeozoic, the Hebei—Shandong fault block situated in the eastern part of the North China plate (commonly named the North China platform) was a gently-inclined shallow marine carbonate platform in which the water depth is shallower in the west and deeper in the east. It was a pericontinental clastic sea during the Early Cambrian. During the Zhangxiaian (Middle Cambrian), a carbonate platform sprouted. The high-energy oolitic shoals and platform-margin beaches were widespread. During the early Late Cambrian, the platform deficient in terrigenous clastics and abundant in carbonate deposits tended to be mature and was occupied widely by the storm deposits and storm beaches. During the Late Cambrian, the platform became shallower in the south and deeper in the north as a result of uplifting. The block was shifted southwards, resulting in the development of the sabkha flats and restricted platform during the Yelian and Liangjiashanian (Early Ordovician). In spite of three stages of rises and falls of sea level, there was the evolution trend towards regression from which the land resulted and the restricted platform was replaced by sabkha flats.
The primary mechanism for the formation and evolution of the carbonate platform include: (1)mature and stable crystalline basement as well as slowly and steadily tectonic activity; (2) favourable palaeolatitudes and palaeoclimates, and (3) sea level rises and falls.
The coincidence of the Early Palaeozoic sea level fluctuations in the North China plate with the global records implies that the present study has provided another important evidence for the interpretation of the global geological history.