First documentation of the Ordovician Guttenberg delta C-13 excursion (GICE) in Asia: chemostratigraphy of the Pagoda and Yanwashan formations in southeastern China

摘要

The only published VC data from the Ordovician of China are from the Lower and Upper Ordovician, and only the latter records include a significant excursion, namely the Hirnantian excursion (HICE). Our recent chemostratigraphic work on the Upper Ordovician (Sandbian-Katian) Pagoda and Yanwashan formations at several localities oil the Yangtze Platform and Chiangnan (Jiangnan) slope belt has resulted in the recognition of a positive delta C-13 excursion that has values of similar to+1.5 parts per thousand above baseline values. This excursion starts a few metres above a stratigraphic interval with B. alobatus Subzone conodonts as well as graptolites of the N. gracilis Zone. The distinctive conodonts Amorphognathus aff. Am. ventilatus and Hamarodus europaeus first occur at, or very near, the excursion interval. Because these conodonts appear in the stratigraphic interval of the Guttenberg VC excursion (GICE) in Estonia, we identify the Chinese excursion as the GICE. This is the first record of the GICE in the entire Asian continent. It confirms that GICE is a global excursion and provides an illustration of how VC chemostratigraphy, combined with new biostratigraphic data, solves the problem of the previously controversial age of the Pagoda Formation and how this classical stratigraphic unit correlates with the Baltoscandian and North American successions.