STRATIGRAPHIC DIVISION AND CORRELATION OF THE DEVONIAN IN THE XICHUAN-NEIXIANGAREA, HENAN PROVINCE

The Devonian is divided into the Middle Devonian Baishangou Formation and the Upper Devonian Wangguangou Formation and Hulushan Formation. Middle Series: The Baishangou Formation consists of purplish-red mudstone and fine-grained quartzose sandstone, containing fossils of the pelecypod Cypricardinia sp. and gastropods. Upper Series: The Wangguangou Formation consists of grayish-yellow argillaceous limestone and gray mudstone, containing fossils of corals and brachiopods, with Disphyllum and Desquantia predominating in the lower part, Cyrtospirifer in the middle part and Tenticospirifer in the upper part. According to the fossil assemblages, its age is considered to be early Late Devonian. The Hulushan Formation is composed of grayish-white thick-bedded middle-fine grained quartzose sandstone and grayish-yellow silty mudstone, containing abundant fossils of brachiopods. Yunnanellina is dominant in the lower part, Tenticospirifer in the middle and Yunnanella in the upper part; towards the top, plat fossils such as Sublepidodendron mirabile and Lepid- odendropsis hirmeri are contained. According to the fossil assemblages. the age is assigned to latest Devonian.