End-Permian catastrophic event of marine acidification by hydrated sulfuric acid: Mineralogical evidence from Meishan Section of South China

Abstract

The event Permian-Triassic boundary (EPTB) is well marked by the famous "white clay" of bed 25 in Meishan Section located in Changxing county, Zhejiang province of China. In this note, the white clay as well as its overlying and underlying sequences is investigated particularly for mineralogical records. The investigation yields three findings that contribute to better understanding the scenario of the EPTB mass extinction. (i) A red goethite-rich microlayer (0.3 mm) is first recognized to be horizontally widespread on the base of the white clay in the section. The microlayer should be considered as a macro geochemical indicator naturally tracing a catastrophic initiation at the EPTB. (ii) An interruption of marine carbonate deposition is discovered due to blank of carbonate minerals in the white clay. The discovery provides significant evidence of a marine acidification event that would occur in the paleo-ocean with marine acidity estimated at pH <4.0 at least and be triggered by the ultimate catastrophic event. (iii) Gypsum as typical sulfate mineral is identified to exist in the white clay with high abundance (34%). The fact reveals that hydrated sulfuric acid would be present at the bottom of the ocean and thus chemically create the marine acidification event. Furthermore, it is suggested that the marine acidification event could not only directly kill some marine biotic species but also result in some derivative events such as the benthic anoxia and the temporal global temperature-increase during the EPTB mass extinction.