Brachiopods and stratigraphy of the Upper Devonian (Frasnian) succession of the Radlin Syncline (Holy Cross Mountains, Poland)

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AbstractThe lower part of the Frasnian succession in the Radlin Syncline (Kielce–Łagów Synclinorium, southern region of the Holy Cross Mountains), in the two studied successions: Józefka at Górno and (for the first time) Radlin, consists of the rhythmic marly Szydłówek Beds, the fossil-rich limestones of the Wietrznia Beds (locally) and the atypically developed, calcareous Kostomłoty Beds. The carbon isotope chemostratigraphic pattern overall corresponds well to the global Early–Middle Frasnian biogeochemical perturbation, even if the majorpunctatapositive excursion is only fragmentarily recorded in the Kostomłoty intrashelf basin.Two brachiopod assemblages are abundantly represented in both sections: thePhlogoiderhynchus polonicusAssemblage, typical of the Szydłówek Beds, and theBiernatella lentiformisAssemblage, limited to the middle part of the Wietrznia Beds. Both are highly dominated by the index species. Twenty nine lower Frasnian brachiopod species (Craniida – 1 species, Strophomenida – 1, Productida – 2, Protorthida – 1, Orthida – 5, Pentamerida – 1, Rhynchonellida – 4, Atrypida – 4, Athyridida – 3, Spiriferida – 4, Spiriferinida – 3) are described from the Szydłówek and Wietrznia Beds. Seven new species are introduced:Skenidioides cretusHalamski sp. nov.,Biernatium minusBaliński sp. nov.,Monelasmina montisjosephiBaliński sp. nov.,Atryparia(Costatrypa)agricolaeHalamski and Baliński sp. nov.,Davidsonia enmerkarisHalamski sp. nov.,Leptathyris gornensisBaliński sp. nov., andEchinocoelia parvaBaliński sp. nov.Davidsonia enmerkarisHalamski sp. nov. is intermediate betweenDavidsoniaBouchard-Chantereaux, 1849 andRugodavidsoniaCopper, 1996 and is the youngest known representative of the suborder Davidsonioidea Copper, 1996.Skenidioides cretusHalamski sp. nov. is the last representative of the genus. Statistical investigation of a large sample ofSpinatrypina(Exatrypa)explanatadid not confirm the existence of two dimorphic forms, coarse- and fine-ribbed.The high-diversityBiernatella lentiformisAssemblage is quite dissimilar to coeval brachiopod assemblages described heretofore from the Holy Cross Mountains region. It is interpreted as consisting of mostly parautochthonous dwellers of deep-slope muddy habitats and a local, occasionally storm-agitated, intra-basin brachiopod-crinoid-coral shoal. The fauna was adapted probably to cooler and nutrient-poor waters during an initial phase of the severe carbon cycle perturbation.