Ziqiu Fm

The type section is lies on the left side of the Linxiangxi sector in the midway from Taoshan to Yuxiakou in Ziqiu Town, Changyang, Hubei; and the reference section is at Tizikou of Maohu Township, Zhicheng City, Hubei. It was named by Xu Shouyong and Yang Deli in 1984.

Claystone to Sandstone. Lower member consists of silty mudstone and sandstone, occasionally intercalated with coal streaks. Upper member is dominated by foliated mudstone and siltstone, intercalated with fine-grained quartz sandstone and very thin (0.04−0.30 m thick) marl. Thickness 15−30 m, with stable lithology and small variation in thickness.

From west to east, it is ~17 m in Jianshi County, 20 m in Badong County, 14.9 m in Changyang County and 27.9 m in Yidu County, changing into the limestone-dominant Hezhou Fm in the Upper member of the formation in Songzi County. The Lower member is similar to the Gaolishan Fm in lithofacies and lithology.

Lower member contains the peak zone of Plant Sublepidodendron mirabile as well as spores Vallatisporites ciliaris, V. vallatus, Lycospora pusilla, Crassispora trychera, Hymenozonotriletes exlanatus, Tumulispora ordinria, etc. The Upper member yield minor amounts of Brachiopod “Productina” tizikouensis and Spores Apiculatisporis aculeatus, Anapiculatisporites microspinosus, Waltzispora planiangulata, W. verrucosa, Umbonatisporites distinctus, etc.

It is interpreted as littoral clastic deposits