Abstract:

Meishan section, located at Changxing County, Zhejiang Province, has been confirmed as the “Golden Spike”. The geochemical event layer lies on the 25th white clay and the 26th black clay. The macro mineral analysis shows that the sedimentary of carbonate is disconnected in the geochemical event layer, especially carbonate minerals is not detected in the clay of the 25th, which is replaced by a plenty of gypsum. The paper includes the characterization and analysis of the gypsum separated from the white clay and the experiment simulating the ancient environment of gypsum formation. The result shows that most gypsum in the 25th white clay of Meishan Section is automorphic crystal particles and part of them grows on particle of stone or clay mineral. The ancient environment of the gypsum formation may be the buffer solution ofHSO^-₄—SO^2-₄and the paper further infers the pH value is between 1.12 and 2.16, which provides  a new evidence for the hypothesis of ocean sulfation near the boundary of Permian and Triassic.

Key words: gypsum, ancient environment, simulation experiment, Meishan section, P/T boundary