Abstract
We report extensive major and trace element data for the Permian-Triassic boundary (PTB) at Meishan, China. Analyses of 64 samples from a 2.5 m section span the last 75 kyr of the Permian and the first 335 kyr of the Triassic, from beds 24 to 34. We also report data for 20 acetic acid extracts that characterize the carbonate fraction. Whole rock major element data reflect the change of lithology from carbonate in the Permian to mudstone and marl in the Triassic, indicate an increase of siliciclastic input and MgO in and above the extinction interval (beds 24f–28), and silica diagenesis in carbonates below the extinction horizon. Above bed 27, enrichment factors calculated with respect to Al and Post-Archean Australian Shale (PAAS) are ∼1 for most trace elements, confirming that siliciclastic input dominates trace element distributions in the Triassic. Within the extinction interval, beds 24f and 26 show increases in As, Mo, U and some transition metals. V, Cr, Co, Ni, Cu, Zn, Pb, and Ba are variably enriched, particularly in bed 26. Below the extinction interval, the top of bed 24d shows enrichment of V, Cr, Co, Ni, Cu, Zn, Pb, and Ba in a zone of diagenetic silicification. Trace elements thus reflect siliciclastic input, diagenetic redistribution, and responses to redox conditions. Trace element patterns suggest either a change in provenance of the detrital component, or a change in the proportion of mechanical to chemical weathering that is coincident with the beginning of the extinction in bed 24f. Ba, Zr, and Zn behave anomalously. Ba shows little variation, despite changes in biological activity and redox conditions. The enrichment factor for Zr is variable in the carbonates below bed 24f, suggesting diagenetic Zr mobility. Zn shows a sharp drop in the extinction horizon, suggesting that its distribution was related to phytoplankton productivity. Rare earth element content is controlled by the siliciclastic fraction, and carbonate extracts show middle rare earth enrichment due to diagenesis. Ce and Eu anomalies are not reliable indicators of the redox environment at Meishan.
Highlights
Every aspect of the geology of the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary (PTB) at Meishan, China (Yin et al, 2001), has been studied in detail
Of the stratigraphic subdivisions of the Meishan section, the data justify division of the section into beds lying above 24e, those lying below 24e, and 24e separately (Figure 2)
We report a survey of major and trace elements in the PTB section at Meishan, China
Summary
Every aspect of the geology of the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary (PTB) at Meishan, China (Yin et al, 2001), has been studied in detail. Acid rain (Black et al, 2014) and elevated atmospheric temperatures probably caused extinction on land (Fielding et al, 2019; Feng et al, 2020), and increased weathering and erosion (Algeo and Twitchett, 2010), because they represent increased nutrient input, likely contributed to a positive feedback on anoxia in at least the surface ocean (Wei et al, 2015; Zhang et al, 2018; Zhang et al, 2020). Increased weathering and erosion impact the 87Sr/86Sr composition of the oceans, so that correlated isotopic and other chemical patterns constrain the timing and mechanisms of extinction
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