CAMBRIAN-ORDOVICIAN STRATIGRAPHY AT LUOYIXI AND WANGCUN, HUNAN PROVINCE, CHINA: STRATOTYPES FOR BASES OF THE WANGCUNIAN AND YOUSHUIAN STAGES, AND CANDIDATE STRATOTYPE FOR THE BASE OF AN UNNAMED GLOBAL STAGE DEFINED BY THE FAD OF LEJOPYGE LAEVIGATA

摘要

Wangcun is an ancient town in southernmost Yongshun County, Hunan Province, China. The town is a significant tourist destination, in part because of its long history and in part because of the attractive riparian scenery along the nearby Mongdonghe River, a branch of the Youshui River. Luoyixi, which is located about 8 km southeast of Wangcun, is a village in Guzhang County that has a railway station to accommodate tourists. The Cambrian in the Wangcun-Luoyixi area is more than 1300 m in thickness. Two lengthy Cambrian sections, the Luoyixi section (or Wangcun South section) and the Wangcun section, have been measured. The sections record lower and the upper parts of the Cambrian System, respectively. The Luoyixi section is exposed near Luoyixi railway station in a roadcut along a recently built highway connecting Zhangjiajie and Jishou on the south bank of the Youshui River (Fengtan Reservoir). The Wangcun section is exposed in a roadcut along the old highway connecting Wangcun and Luoyixi on the north bank of the River (Figs. 1, 3). The old highway was constructed for the benefit of travelers arriving at the Luoyixi railway station, and has not been used for most traffic since the Zhangjiajie-Jishou highway was built in 2003. The sections are situated on the southeast limb of an undulating syncline, the Liexi-Zhuitun Syncline (Fig. 2), which is one of the major synclines extending through the Jiangnan Slope Belt in northwestern Hunan. Strata exposed in the syncline include those of the lower Cambrian through Lower Ordovician. The trend of the structure is north-northeast.