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2 2022

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The pre-Taghanic (Givetian, Middle Devonian) ecosystems of Miłoszów (Holy Cross Mts, Poland)

Halamski Adam T., Baliński Andrzej, Racki Grzegorz, Amler Michael R. W., Basse Martin, Denayer Julien, Dubicka Zofia, Filipiak Paweł, Kondas Marcelina, Krawczyński Wojciech, Mieszkowski Radosław, Narkiewicz Katarzyna, Olempska Ewa, Wrzołek Tomasz, Wyse-Jacson Patrick N., Zapalski Mikołaj K., Zatoń Michał, Kozłowski Wojciech

Annales Societatis Geologorum Poloniae

2022

Vol. 92, No. 4

323--379

The middle and upper parts of the Skały Fm, Early to Middle Givetian in age, were investigated in four sections at Miłoszów Wood in the Łysogóry Region (northern region of the Holy Cross Mountains, central Poland). The dating is based on conodonts (Polygnathus timorensis Zone to the later part of the Polygnathus varcus/Polygnathus rhenanus Zone; early Polygnathus ansatus Zone cannot be excluded) and spores (Ex1–2 subzones) and, coupled with cartographic analysis and geophysical investigation, allows correlation within the strongly faulted succession. Significant lateral facies variations within the carbonate ramp depositional system in comparison with the better studied Grzegorzowice–Skały section, about 3 km distant, are documented, thanks to conodont-based correlation of both successions. Foraminifers, fungi, sponges, rugose and tabulate corals, medusozoans, microconchids and cornulitids, polychaetes (scolecodonts), molluscs (bivalves, rostroconchs, and gastropods), arthropods (trilobites and ostracods), bryozoans, hederelloids, ascodictyids, brachiopods, echinoderms (mostly crinoids, rare echinoids, holuthurians, and ophiocistoids), conodonts, fish, plants (prasinophytes, chlorophycophytes, and land plant spores), and acritarchs are present. Brachiopods are the most diverse phylum present (68 species), other richly represented groups are bryozoans and echinoderms; in contrast, cephalopods and trilobites are low in diversity and abundance. The muddy, middle to outer ramp biota (200 marine taxa, including 170 species of marine animals, 22 photoautotrophs, 6 forams) represents a mixture of allochthonous shallower-water communities (upper BA3), including storm- and possibly tsunami-affected coral mounds, and autochthonous deep-water soft-bottom brachiopod (e.g., Bifida–Echinocoelia) communities (BA 4–5). The richness and diversity of the Miłoszów biota is relatively high, comparable with other approximately coeval pre-Taghanic ecosystems during the Devonian climatic deterioration (cooling). Preliminary data indicate that in the Holy Cross Mountains, no large-scale replacement of brachiopod (and probably many other benthic ones, like crinoids) communities took place between the Early–Middle Givetian and the Early Frasnian, in contrast to the demise of the Hamilton/Upper Tully fauna in the Appalachian Basin. Such a similarity of pre- and post-Taghanic faunas does not exclude the occurrence of environmental perturbations and transient community turnovers, caused by immigrations during the Taghanic Biocrisis, but evidences the successful recovery of the indigenous biota.

Episkeletobionts of large rugose corals from the Middle Devonian mesophotic palaeoenvironment recorded in the Pokrzywianka Beds (Holy Cross Mountains, Poland)

Zatoń Michał, Malec Jan, Wrzołek Tomasz, Kubiszyn Beata, Zapalski Mikołaj K.

Annales Societatis Geologorum Poloniae

2022

Vol. 92, No. 4

465--484

Organisms encrusting corals from a coral horizon encountered in a trench in the Middle Devonian (Givetian) Pokrzywianka Beds of the classic Grzegorzowice-Skały section in the Holy Cross Mountains, Poland, are described and analyzed in the context of their palaeoecological and palaeoenvironmental background. These episkeletobionts form rather a low-diversity community, dominated by microconchid tubeworms, crinoids, and tabulate corals. The last group, however, is especially diverse at the family level, represented by auloporids, alveolitids, coenitids and favositids. These episkeletobionts are considered to have developed in a low-light, lower mesophotic palaeoeonvironment, as evidenced by the presence of platy, alveolitid tabulate coral in the deposits studied. This microconchid-crinoid-tabulate-coral community differs from other Givetian communities from the Holy Cross Mountains (Laskowa and Miłoszów), which also are considered to have developed in low-light habitats. The differences in taxonomic composition of episkeletobionts between these three localities most probably resulted from specific local conditions, related to bathymetry (light levels, nutrient levels), the specific nature of the hosts/substrates occupied, and also differences in larval dispersal patterns. This, in turn, shows that various encrusting communities may have inhabited seemingly similar, marine habitats within a given time interval and neighbouring areas, which may have serious implications for large-scale comparisons of biodiversity within a given palaeoenvironment.