Facies analysis and sea-level change at the Guadalupian–Lopingian Global Stratotype (Laibin, South China), and its bearing on the end-Guadalupian mass extinction

Abstract

The Guadalupian–Lopingian boundary stratotype at Penglaitan, and the nearby Tieqiao section, near Laibin, South China, record a series of major environmental changes within the Jiangnan Basin during a Mid-Permian biotic crisis. The sequence-stratigraphic, petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations have been assayed. Mass extinction of fusulinid foraminifers is most clearly associated in time with onset of volcanism and a relative sea-level fall that led to the establishment of mid-ramp conditions (Laibin Limestone) in settings that were previously dominated by radiolarian mudstones. The regression also coincides with a low point of 87 Sr/ 86 Sr ratios. The lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the Emeishan flood basalt province 800 km to the west of Laibin. Thus, unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event. Subsequent environmental changes included transgression, spread of dysoxic waters, indicated by populations of small pyrite framboids, and a major negative C-isotope excursion. All these phenomena have been previously related to the end-Guadalupian extinction but they in fact post-date the crisis because a post-extinction fauna of foraminifers is encountered at this time.

High‐resolution Lopingian (Late Permian) timescale of South China

“…According to some recent detailed studies (Wang et al, , 2007Cao et al, 2009), the 87 Sr/ 86 Sr value of Bed 6c just below the GLB GSSP at the Penglaitan Section is 0.706712 , then gradually increases across the GLB (Figure 1). The 87 Sr/ 86 Sr curve provided by Wignall et al (2009b) around the GLB at Penglaitan shows that the Sr ratio falls from 0.7073 at the base of the Laibin Limestone to 0.7069 (lowest value around GLB at Penglaitan) at the top (Bed 6k) before rising again to 0.7072 in the lower Heshan Formation, which are higher than the values, but a generally similar trend of Wang et al …”

Mineralogy and geochemistry of claystones from the Guadalupian–Lopingian boundary at Penglaitan, South China: Insights into the pre-Lopingian geological events

“…The recently established G/L boundary of the Global Stratotype Section and Point (GSSP) at Penglaitan, Laibin, Guangxi (Jin et al, 2006) provides a good opportunity to mitigate this shortcoming. Paleontological, petrographic and sequence-stratigraphic records in this section Wang et al, 2004;Jin et al, 2006;Shen et al, 2007;Chen et al, 2009;Wignall et al, 2009b;Yang et al, 2009) yielded useful insights into the G/L boundary events. However, absolute isotopic dating of the G/L boundary is still lacking, which is critical for the GSSP studies and for the temporal link between the G/L boundary extinction and the Emeishan volcanism.…”

Reply to comment on ‘Paleokarst on the top of the Maokou Formation: further evidence for domal crustal uplift prior to the Emeishan flood volcanism’ by Bin He, Yi-Gang Xu, Jun-Peng Guan & Yu-Ting Zhong, Lithos 119 1–9, 2010

“…In the Penglaitan GSSP Guadalupian-Lopingian Section, a combination of sequence stratigraphic analysis and conodont biostratigraphy shows that this global sea level change occurred in the late Capitanian Stage or J. Xuanhaneiss (Wignall et al, 2009b). Emergence in the areas beyond the ELIP occurs in the J. granti Zone.…”

“…Ukstins Peate et al (2011) contend that there is a continuity of carbonate deposition and a lack of erosion prior to the Emeishan volcanism (e.g., Jin and Shang 2000;Sun et al, 2010;Wignall et al, 2009b). However, all but one of the studies cited in support of their argument focus on sections located at the margins and rifted trenches of the ELIP, and are not within the inner and intermediate zones of the Lithos 125 (2011Lithos 125 ( ) 1009Lithos 125 ( -1011 ELIP.…”

“…Ukstins Peate et al (2011) cite the Penglaitan GSSP section (Jin and Shang, 2000;Wignall et al, 2009b) to support their continuous deposition model. However, this section is located in the area beyond the edge of the ELIP and so cannot be used to argue for a "continuous" contact in the inner zone of the ELIP.…”