Zdarzenie na granicy fran-famen w regionie świętokrzyskim a najważniejsze grupy bentosu

Abstract

THE FRASNIAN-FAMENNIAN EVENT IN THE HOLY CROSS AREA, AND THE MOST IMPORTANT BENTHIC GROUPS Summary The Frasnian-Famennian boundary represents one of the most important mass extinction events in the Phanerozoic, manifesting itself mostly by the worldwide decline of stromatoporoid-coral reefs. The current paleontologic and stratigraphic research in the Holy Cross Mts., Poland, reveals variable patterns of taxonomic diversity of particular fossil groups (figs. 1-4). During the Frasnian the decline of stromatoporoids is evident while the rugose corals show the opposite trend (fig. 1). At the F/F boundary the crisis is marked by a total disappearance of stromatoporoids, corals (fig. l) and crinoids (fig. 3), and termination of numerous important lineages of brachiopods, e.g. reef-associated atrypids and pentamerids (fig. 2). The coelenterate-dominated reef biotas of the Holy Cross Mts. collapsed prior to the F/F boundary, that is not later than the linguiformis Zone. Only small cyanophycean (thrombolitic?) buildups developed locally in the early Famennian in this area. Stepwise patternsof extinction and subsequent recovery are well-recorded in the part of considerably affected shelf areas. The pelagic-ridge ecosystem of the Famennian type was introduced not earlier than in the crepida Zone along with stabilization of environmental conditions on the shelf.