Exploring the end‐Ordovician extinctions in Hirnantian near‐shore carbonate rocks of northern Guizhou, SW China: A refined stratigraphy and regional correlation

Abstract

Richly fossiliferous Hirnantian shelly strata of near‐shore facies in northern Guizhou, South China, known as the Kuanyinchiao Formation, superbly record glacioeustatic sea‐level fluctuations and benthic faunal turnover. Recent studies of the temporal and spatial distribution of these carbonates and shelly fossils permit a critical stratigraphic revision and establishment of a robust regional stratigraphic correlation. The formation is revised to include three informal subdivisions, that is, units A, B, and C, in ascending order. Unit B of the formation typically is dominated by peloidal or oolitic grainstones, and unit C is composed of skeletal wackestone and calcareous mudstone, both units sharing distinctive coral and brachiopod faunas. This contrasts sharply with unit A of the formation, consisting of mudstone, silty mudstone, or calcareous mudstone, that yields the cool‐water Hirnantia fauna and associated coral fauna. In view of the presence of carbonate ooids and peloids, rugose corals, and a distinctive brachiopod assemblage, all indicative of warm‐water conditions, unit B, as well as unit C yielding the same shelly fauna, is interpreted as representing postglacial sedimentation immediately following the major Hirnantian glaciation, thus marking a significant climatic shift. Similar warm‐water carbonate rocks have been recognized in a number of regions along the margin of the Qianzhong Oldland, including Bijie, Renhuai, Tongzi, and Fenggang of northern Guizhou. Such a vast distribution area of these rocks indicates that postglacial carbonates are more widespread on the Yangtze Platform of South China than previously thought, providing a rare window into rocks and fossils of the survival interval immediately following the extinction event associated with the Hirnantian glacial episodes.

A latest Ordovician Hirnantia brachiopod fauna from western Yunnan, Southwest China and its paleobiogeographic significance

“…Most of the typical components of the Hirnantia fauna are cosmopolitan. The provincialism detected, however, may be due to poor correlation (e.g., with Edgewood fauna, seeWang et al, 2018), or different facies, rather than due to its paleogeographical distribution. This will be discussed in more detail by Rong et al in a forthcoming review paper.…”

Constraining the biotic transitions across the end‐Ordovician mass extinction in South China: Bio‐ and chemostratigraphy of the Wulipo Formation in the Meitan area of northern Guizhou

“…The Shiqian Formation of the Shiqian area was previously considered to be the only postglacial warm-water record of late Hirnantian age in South China (Wang et al, 2016(Wang et al, , 2017(Wang et al, , 2018. Our revised age assignment of the Wulipo Formation suggests a much wider distribution in the region of near-shore carbonates and benthic faunas during the late Hirnantian than previously envisaged, and, together with available data (Wang et al, 2015(Wang et al, , 2016(Wang et al, , 2018, results in an updated chronostratigraphic classification of rocks spanning the Ordovician and Silurian boundary on the Yangtze Platform of South China (Figure 8).…”

“…where Hirnantian near-shore carbonates and fossils are best represented. Our previous studies have made critical stratigraphic revisions of these rocks in the region (Wang et al, 2015(Wang et al, , 2018Wang, Zhan, & Percival, 2016), contributing to an improved understanding of the pattern and dynamics of the EOME (Wang et al, 2019;Wang, Zhan, Huang, & Percival, 2017).…”

A nearshore Hirnantian brachiopod fauna from South China and its ecological significance

“…The Kuanyinchiao Beds were also named the Kuanyinchaio Formation (e.g., Wang et al, 2018). However, due to its limited thickness, which is mostly less than 2 meters, we retain the term Kuanyinchiao Beds in this study.…”

“…In many localities in the nearshore facies belt, the beds are split into two parts on lithological differences, such as those in Bijie, Renhuai, Tongzi, Fenggang, and Yinjiang, northern Guizhou, South China. The lower bed is commonly a gray-black mudstone whereas the upper bed is argillaceous limestone (Wang et al, 2018).…”