Palaeoenvironmental changes at the Frasnian/Famennian boundary in key European sections: Chemostratigraphic constraints

摘要

The study aims to put constraints on global environmental changes, which took place during the Frasnian-Famennian (F/F) transition by using a geochemical multiproxy approach. For this several key European F/F boundary sections deposited in different palaeogeographic settings were selected, including, in addition to the stratotype and parastratotype sections of Coumiac (Montagne Noire, France) and Steinbruch Schmidt/Branau (Germany), respectively, also, some other sections thoroughly characterized by other authors (the drilling Budesheimer Bach/Prumer Mulde, Germany; Kowala Section, Holy Cross Mountains, Poland; La Serre, France). Changes in the detrital flux along the sections were evaluated on the basis of both variations in mineral composition and in some diagnostic element ratios like Ti/Al. The biogenic flux was assessed as a function of the C-org content. The input of nutrients or the palaeoproductivity was determined by the P2O5 and Ba in excess. The degree of anoxia during deposition was constrained by determining the concentration of redox sensitive metals (e.g., Fe, Mn) in the bulk sediment, of specific element ratios (e.g., V/Cr), as well as the size of pyrite grains together with the degree of pyritization (DOP) in the Budesheimer Bach core. The hydrothermal and volcanic influence in the sedimentary record was detected using, e.g., the Al/(Al+Fe+Mn) and Zr/Al2O3 ratios.