Marcasite at the Permian?Triassic Transition

Abundant pyrite in black shales at the Permian-Triassic Boundary (PTB) from several localities around world has been regarded as evidence of oceanic anoxia during end-Permian mass extinction (EPME). However, a significant amount “pyrite” these rocks is not actually but marcasite, orthorhombic polymorph FeS2. Marcasite particularly sensitive to changes pH and fO2, which theoretically enables it be utilized proxy for geochemical marine environment. Moreover, its abundance PTB suggests that major occurred this time global ocean. In chapter, we present stable isotope trace element compositional data both marcasite pyrite, were identified stratigraphic interval representing EPME, along with bulk-rock chemostratigraphic Kockatea Shale, Perth Basin, Australia. We compare marcasite-pyrite intergrowth textures sedimentary sequences Meishan D (MD), Opal Creek (OC), Ubara (Ub), Shale (KS), represent shallow continental shelves ancient Tethys Ocean (KS, MD) abyssal plains Panthalassic (Ub, OC) end Permian. The textures, geochemistry, sulphur isotopic analyses samples favor synsedimentary early diagenetic origin sulfides, further supporting notion EPME was least partially caused by large-scale drop ocean PTB. A review other globe, including pre- post-Permian sections, indicates sedimentary-diagenetic may more abundant rock record than previously recognized, carries implications geochemistry environment through geologic time.