Warunki depozycji szczątków kręgowców w osadach środowisk okołopływowych dolnego wapienia muszlowego (anizyku) w kopalni „Stare Gliny” koło Olkusza

Michał Matysik, Dawid Surmik


Depositional conditions of vertebrate remains within the Lower Muschelkalk (Anisian) peritidal carbonates of the “Stare Gliny” quarry near Olkusz (Kraków-Silesia region, southern Poland).
A b s t r a c t. A detailed sedimentological study of the Lower-Middle Muschelkalk (Middle Triassic) carbonate succession exposed at the “Stare Gliny” quarry near Olkusz (Kraków-Silesia region, southern Poland) revealed numerous vertebrate remains within its lowermost sedimentary unit. This 7-m-thick package onlaps a gently-inclined surface of a paleoisland made of the Devonian (Givetian) dolostones, and was deposited during a transgressive phase of the second Middle Triassic transgression onto the southern Poland. The package consists largely of: 1) unfossiliferous dolosiltites and fine-grained dolarenites, the tops of which commonly contain root molds and small-scale karstic forms; 2) breccias (minor conglomerates) with lithoclasts of Givetian dolostones; 3) dolocretes; and 4) dolomitic shales. This lithofacies association represents a restricted lagoon which experienced longer periods of emersion. A minor occurrence of cryptalgal laminites reflects only temporary sedimentation in the intertidal zone of a tidal flat. The bone fragments occur within all types of lithofacies, but the macroscopically distinguishable specimens have been found exclusively in the dolocretes. The poor preservation and advanced disarticulation of bones hinder unequivocal assessment of their affinity. The small size of bones suggests that they represent prolacertiforms (perhaps juvenile Macrocnemus) or other small archosauromorphs similar in sizes to Protorosaurus or Czatkowiella whose remains were found in the 1950s within cave deposits, in the same outcrop. Macrocnemus widely inhabited Middle Triassic lagoons and tidal flats across Paleo-Europe and thus seems to fit well to the peritidal setting surrounding the “Stare Gliny” paleoisland. The bone-bearing package occurs 30 metres below the 5-m-thick oncolitic package that is widely regarded as a correlation
horizon over the entire Kraków-Silesia region, and 15 metres below the sequence boundary marking the top of the Górażd¿e Beds in the Opole region and the Olkusz Beds in the Kraków-Silesia region. On the basis of these correlations, a conclusion can be made that the vertebrate assemblage is Bithynian/Pelsonian (middle Anisian) in age.

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