EVOLUTION OF NORTH CHINA-TYPE EARLY CAMBRIAN SEDIMENTARY ENVIRONMENTS AND TRACE FOSSIL ASSEMBLAGES IN HENAN PROVINCE

Except the Canglangpuian and Longwangmiaoian (Early Cambrian) sediments, no the Meishucunian and Qiongzhusian sediments have been noticed up to now in Henan Province. For instance, the Xinji and Zhushadong Formations (Canglangpuian) and the Mantou Formation (Longwang-miaoian) are distributed over the region south of the Jiyuan-Bo'ai-Wuzhi zone, whereas in the region north of it the Xinji and Mantou Formations (Longwangmiaoian) occur. It is clear that the Xinji Formation is a diachronous stratigraphic unit formed in a specific environment.
The evolution of the Early Cambrian sedimentary environments in the study area may be generalized as follows. The early and middle Canglangpuian (Early Cambrian) Xinji Formation was de-posited in the subtidal shallow-water shelf and littoral tidal flat-subtidal zones,and the littoral tidal flat-intertidal zone;the middle and late Canglangpuian Zhushadong Formation was confined to the littoral carbonate tidal flats-ramps-intertidal and supratidal evaporative flats,intertidal evaporatic depressions and subtidal carbonate shallow-water ramps,and the Longwangmiaoian Mantou Formation was laid down in the littoral carbonate tidal flats-ramps and subtidal carbonate shallow-water ramps.
The Early Cambrian trace fossils in the region occur dominantly in three horizons,including H-T and L-B assemblages, The former represents the trace fossil assemblages in the shallow-water shelf storm environments, whereas the latter represents those in the intertidal-supratidal low-energy mud-flat environments.
11 genera and 16 species of trace fossils are described in detail in this paper.