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

Baliński A., Racki G., Halamski A. T.

Acta Geologica Polonica

2016

Vol. 66, no. 2

125--174

The 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 major punctata positive excursion is only fragmentarily recorded in the Kostomłoty intrashelf basin. Two brachiopod assemblages are abundantly represented in both sections: the Phlogoiderhynchus polonicus Assemblage, typical of the Szydłówek Beds, and the Biernatella lentiformis Assemblage, 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 cretus Halamski sp. nov., Biernatium minus Baliński sp. nov., Monelasmina montisjosephi Baliński sp. nov., Atryparia (Costatrypa) agricolae Halamski and Baliński sp. nov., Davidsonia enmerkaris Halamski sp. nov., Leptathyris gornensis Baliński sp. nov., and Echinocoelia parva Baliński sp. nov. Davidsonia enmerkaris Halamski sp. nov. is intermediate between Davidsonia Bouchard-Chantereaux, 1849 and Rugodavidsonia Copper, 1996 and is the youngest known representative of the suborder Davidsonioidea Copper, 1996. Skenidioides cretus Halamski sp. nov. is the last representative of the genus. Statistical investigation of a large sample of Spinatrypina (Exatrypa) explanata did not confirm the existence of two dimorphic forms, coarse- and fine-ribbed. The high-diversity Biernatella lentiformis Assemblage 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.

Porównanie podatności magnetycznej (MS) i wskaźników geochemicznych środkowego i górnego franu w Kanadyjskich Górach Skalistych: implikacje dla analiz paleoklimatycznych i paleośrodowiskowych oraz interpretacji zdarzenia punctata

Śliwiński M. G., Whalen M., Day J.

Przegląd Geologiczny

2010

Vol. 58, nr 12

1152-1160

Ongoing magnetostratigraphic and geochemical studies (including major and trace element geochemistry and stable isotopes of C, N, O) in the Canadian Rocky Mountains are providing insight into the paleoenvironmental changes of the mid-Frasnian punctata Event, a prominent marine geochemical perturbation. The data is evaluated with 1) a regional sequence stratigraphic perspective and 2) within the context of a rapidly changing Late Devonian world, characterized by numerous sedimentological and faunal perturbations leading up to the eventual Frasnian-Fammenian (F/F) mass extinction. Proxies for bottom water paleoredox conditions (Mo, V, U), oceanic primary productivity (δ13Corg, δ15Nbulku, Cu, Ni, Ba), changes in detrital input (Si, Al, K, Ti, Zr), and magnetic susceptibility display similar trends, indicating that these proxies and MS variations are inherently linked. The observed excursions suggest that changes in detrital input were the main driver of a bioproductivity increase. Elevated organic matter export from the photic zone likely led to the deposition and later preservation of organic-carbon rich facies under facilitated conditions of bottom water suboxia-anoxia. These geochemical trends were likely influenced by eustatic sea level change, but may have been enhanced by pulses of coincident orogenic activity and pulses of terrestrial afforestation. The rise and expansion of the first true forests is thought to have drastically altered nutrient fluxes to the oceans via increases in pedogenesis and the expansion of a mature soil profile. Our work is intended to complement the growing body of research aimed at elucidating the causes and understanding the effects of terrestrial and marine events of the P. punctata biozone and, more broadly, at understanding the Earth-system changes of the Late Devonian leading up to the F/F boundary.