![[Visit Client Website]](/img/gsa/banner.jpg)
Paper No. 4
Presentation Time: 1:30 PM-5:30 PM
THE FIRST RECORD OF THE ORDOVICIAN GUTTENBERG δ13C EXCURSION (GICE) IN ASIA: CHEMOSTRATIGRAPHY OF THE PAGODA LIMESTONE AND YANWASHAN FORMATION IN SOUTH-EASTERN CHINA
Very few chemostratigraphic data have so far been published from the Ordovician of Asia. In China, the currently available information includes only some δ13C data from the Lower Ordovician and the Hirnantian near Yichang, Hubei. The Hirnantian values indicate the presence of the globally distributed Hirnantian δ13C excursion (HICE). Our recent chemostratigraphic work on the Upper Ordovician Pagoda Limestone, one of the lihologically most distinctive and geographically widespread Ordovician units in China, has resulted in the recognition of a significant positive δ13C excursion of ~2 above the baseline values at several Pagoda Limestone localities on the Yangtze Platform (e.g. Beigongli and Xiaotan, Anhui). A similar positive δ13C excursion occurs in the upper Yanwashan Formation, a partial correlative of the Pagoda Limestone, at Huangnitang, Zhejian in the Jiangnan deeper-water slope belt. This excursion starts a few m above strata with B. alobatus Subzone conodonts as well as graptolites of the N. gracilis and C. bicornis zones. The distinctive and widespread conodont Hamarodus europaeus first appears at, or near, the excursion interval. The stratigraphic position of this excursion in China is the same as that of the Guttenberg excursion (GICE) in sections in Baltoscandia and hence, it is justified to identify the Chinese excursion with the GICE. This is the first record of the GICE in China as well as in the entire Asian continent, and it supports the idea that the GICE has a worldwide distribution. The new chemostratigraphic data, combined with new information from conodont biostratigraphy, provide the first decisive clues to the long controversial precise age of the Pagoda Limestone and its correlation with Baltoscandian and North American units. In terms of the recently introduced global Ordovician stage classification, the Pagoda Limestone is of early to middle Katian age.