黔西威寧岔河陸相二疊系－三疊系界線粘土岩研究－基於X射線衍射、掃描電鏡分析

Applying the concept of the Permian-Triassic Boundary Stratigraphic Set (PTBST) to the non-marine Permian-Triassic boundary (PTB) sections in Western Guizhou Province, South China, we have found that the clayrocks of the PTB in these sections have the same origin and exhibit a remarkably similar vertical succession to similar rocks found at the marine Permian-Triassic boundary of the Meishan Section. The X-ray diffraction and scan electronic microscope studies of some clays and/or mudstones from the Chahe Section, indicate that the composition of the clays in the PTBST (beds 66f-68a) is very different from that of the clays found either under or above the PTBST beds of the same section. The clay minerals in the clayrocks of the PTBST are mainly composed of illite-montmorillonite interlayers, with few montmorillonites and chlorites. Whereas the other clayrocks and/or mudstones underlying and overlying the PTBST are made of chlorites and/or kaolinites. Some special mineral contents, such as hexagonal dipyramid quartz, zircons and few spherules, and the abnormal contents of some elements are only found in the calyrocks in the PTBST. These particular characteristics of the PTBST clayrocks are attributed to their special volcanic formation and thus provide a reliable auxiliary marker for high-resolution demarcation of the terrestrial PTB.