Paleoenvironments and geochemistry across a continuous Permian–Triassic boundary section at B?kk Mountains, Hungary

• 作者: M.E.Brookfield J.C.Williams A.G.Stebbins
• 来源期刊: 地学前缘（英文版）
• 年，卷（期）: 2021,（3）
• 所属期刊栏目: Research Paper
• 页码范围: 214-233
• 页数: 20页
• 语种: 英文

摘要

The Bálvány North Permian-Triassic boundary sediments were deposited on a carbonate platform in the tropical part of the western PaleoTethys ocean. The overall elemental geochemistry of the detailed two-metre-thick sec-tion across the boundary that we studied shows that the clastic content of the sediments came from dominantly silica-rich continental sources though with some more silica-poor inputs in the uppermost Permian and lowest Triassic limestones as shown by Ni/Al and Nb/Ta ratios. These inputs bracket, but do not coincide with, the main extinctions and associated C, O and S changes. Increased aridity at the Permian-Triassic boundary with in-creased wind abrasion of suitable Ti-bearing heavy minerals accounts for both the high Ti/Al and Ti/Zr ratios. Var-ious geochemical redox proxies suggest mainly oxic depositional conditions, with episodes of anoxia, but with little systematic variation across the Permian–Triassic extinction boundary. The lack of consistent element geo-chemical changes across the Permian-Triassic boundary occur not only in adjacent shallower-water marine sec-tions, and in other marine sections along the SW Tethys margin such as the Salt Range sections in Pakistan, but also in deeper shelf and oceanic sections, and in non-marine African and European continental sediments. In the absence of significant changes in physical environments, chemical changes in the atmosphere and oceans, reflected in various isotopic changes, drove the Permian–Triassic extinctions.