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Ambiguities in conchostracan biostratigraphy : a case study of the Permian–Triassic boundary

Becker A.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 4

697--701

EN

In recent years, conchostracan biostratigraphy has become a popular tool for the recognition of the Permian–Triassic boundary and for the chronostratigraphic subdivision of the Triassic in intracontinental settings, including also the bone-bearing Keuper strata of Poland. The ambiguous nature of the new bio-chronostratigraphic approach was characterized in a case study of the Permian–Triassic boundary interval. The most important problems were: (1) the lack of documentation of the index species, (2) the indirect correlation with the conodont stratigraphy in marine reference sections through the sporomorph spectra, (3) the lack of definition and documen- tation of supporting palynologic zones, and (4) difficulties in reliable taxonomic determination of Conchostraca. Testing and, if necessary, revision of the zonation by several independent research groups is suggested.

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Pstry piaskowiec w Górach Świętokrzyskich: chronostratygrafia i korelacja litostratygraficzna z basenem turyńskim

Ptaszyński T., Niedźwiedzki G.

Przegląd Geologiczny

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2006

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Vol. 54, nr 6

525-533

EN

The study was performed to attempt the lithostratigraphic correlation of the Buntsandstein in the margin of Holy Cross Mountains region with that of the Thuringian Basin, and simultaneously, to clarify its position in the chronostratigraphic scheme, basing on biostratigraphic data (microflora, conchostracans), and on the existence of regional discordances. The authors found strong analogies with other Buntsandstein sections of the Europe. On the other hand, because of the position of the studied area within the marginal part of the Central European Basin, Buntsandstein of the Holy Cross Mountains region is developed in different facies, more fluvial, instead of lacustrine ones. The common presence of Conchostraca representing the same species as in other parts of the Central European Basin (Thuringia), enables possible the correlation of the investigated area with the Thuringian Basin, and helps to locate stratigraphic gaps and discordances. The authors found that the lower boundary of the Buntsandstein and the boundary between the Lower and Middle Buntsandstein in the Polish study area are not equivalents of those in other areas. Also note worthy is the presence at the margin of the Holy Cross Mountains of youngest Permian terrigenous deposits not connected with the Zechstein salinar sedimentation, included to date to Zechstein or to Buntsandstein. The key for understanding the lithostratigraphic scheme of the Buntsandstein of Holy Cross Mountains region is an assumption, that the Zagnańsk Formation is mostly of fluvial, instead of lacustrine origin, consisting of equivalents of the whole Lower Buntsandstein, and that of the lower Volpriehausen Formation of the Middle Buntsandstein, with the Volpriehausen discordance present within. Authors also assume, that at least in this case, differences in the marginal part of the sedimentary basin, in comparison with its central part, depend on the presence of fluvial facies instead of lacustrine ones, and onthe presence of sedimentary gaps and discordances whose duration is progressively longer towards the basin margin enlarges in the direction to the basin margin.

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Conchostraca [muszloraczki] z najniższego pstrego piaskowca Zachełmia, Góry Świętokrzyskie

Ptaszyński T., Niedźwiedzki G.

Przegląd Geologiczny

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2004

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Vol. 52, nr 12

1151--155

EN

Contemporary Conchostraca [clam shrimps] live in temporary and permanent freshwater ponds and pools. They have wide geographic distribution. Their fossils are abundant in the Buntsandstein and very important markers for chronostratigraphic correlation between marine and continental sections. The conchostracan assemblage found in the lowermost Buntsandstein at Zachełmie quarry: Falsisca postera, Falsisca eotriassica, Palaeolimnadia cf. cishycranica, Euestheria ex gr. gutta, Euestheria gutta oertlii indicates the uppermost Permian age of at least the most of Jaworznia Formation [A1 petrographical complex], cropping out at the Zachełmie quarry in the Holy Cross Mountains, Poland.