The biotic fossils from the Upper Carboniferous Zhouying Formation in the Xichuan district,southwestern Henan

There occur various biotic fossils in the Upper Carboniferous Zhouying Formation in the Xichuan district,southwestern Henan. They are fusulinids,ammonites,corals,brachiopods,bivalves,gastropods,crinoids,bryozoans,foraminifera and plant remains. The fusulinids appear as the Late Carboniferous standard fossils,while the ammonites,corals,brachiopods,bivalves and gastropods are generally characteristic of the Devonian biotic fossils. The integration of lithology,sequences,ecology and sedimentary environments suggests the Late Carboniferous sedimentary strata of the Zhouying Formation. The Late Carboniferous,Middle and Late Devonian biotic assemblages are the characteristic products in the Xichuan district developed in the barried restricted lag basins. The sea water encroachment and deepening and enrichment of organic matter are favourable for the generation and development of the biotas in the Formation. The marine regressions,salification of sea water and lack of food in the relatively enclosed conditions are responsible for the extinction of the biotas and burial and preservation of their fossils.