Latest Maastrichtian foraminiferal assemblages from the Husów region (Skole Nappe, Outer Carpathians, Poland)
The Ropianka Formation (also known as the Inoceramian Beds) in the marginal part of the Skole Nappe (Husów region, the Gaj section) contains abundant, diverse and well preserved assemblages of Maastrichtian planktonic and benthic foraminiferids, assigned to the middle-upper part of the Gansserina gansseri Zone and to the Abathomphalus mayaroensis Zone. The composition of the assemblages indicates fluctuations of organic matter flux to the marginal part of the Skole Basin floor in the studied interval. The studied taxa are typical of the "transitional zone" between the Tethyan and the Boreal domains. The disappearance of planktonic foraminifers in the uppermost part of the section and appearance of some agglutinated taxa (Rzehakina fissistomata; abundant Conglophragmium irregularis and Glomospira charoides) points to a Paleocene age.
The Cretaceous-Paleogene boundary in turbiditic deposits identified to the bed: a case study from the Skole Nappe (Outer Carpathians, southern Poland)
The Cretaceous-Paleogene (K-T) boundary has been recognized in turbiditic sediments of the Ropianka Formation in the Skole Nappe (Bąkowiec section) on the basis of planktonic foraminiferids with an accuracy of 40 cm. Such precise determination of the K-T boundary for the first time in the Carpathians and in turbiditic flysch sediments in general was possible due to the successive occurrence of the Early Paleocene planktonic taxa of the P1 Zone above the latest Maastrichtian Abathomphalus mayaroensis Zone with the Racemiguembelina fructicosa Subzone. The trends in composition of the latest Maastrichtian foraminiferal assemblages are similar to the Gaj section from the adjacent thrust sheet, probably due to the influence of the same paleoenvironmental factors.
Ichnology of Upper Cretaceous deep-sea thick-bedded flysch sandstones: Lower Istebna Beds, Silesian Unit (Outer Carpathians, southern Poland)
The Ophiomorpha rudis ichnosubfacies of the Nereites ichnofacies was recognized in thick- and very thick-bedded sandstones of the Lower Istebna Beds (Campanian-Maastrichtian), which were deposited mainly in deep-sea clastic ramps and aprons. It contains mainly Ophiomorpha rudis (produced by deeply burrowing decapod crustaceans) and rarely Zoophycos isp. and Chondrites isp. The impoverished Paleodictyon ichnosubfacies of the Nereites ichnofacies is present in the medium- and thin-bedded packages of flysch sandwiched between the thick- and very thick-bedded sandstones. They contain Chondrites isp., Phycosiphon incertum, Planolites isp., Arthrophycus strictus, Thalassinoides isp., Ophiomorpha annulata, O. rudis, Scolicia strozzii and Helminthorhaphe flexuosa. The relatively low diversity of this assemblage is influenced by limited areas covered by muddy substrate, which favours deep-sea tracemakers, and partly by a lowered oxygenation in the sediment.
Alfred Uchman, Hans Egger and Francisco J. Rodríguez-Tovar
The Untersberg section (Northern Calcareous Alps, Austria) provides an expanded and biostratigraphically well constrained deep-sea record of the Paleocene–Eocene transition in the north-western Tethyan realm. At the base of the Eocene, massive carbonate dissolution and a shoaling of the calcite compensation depth (CCD) by at least 1 km is recorded by 5.5 m-thick red claystone, which is intercalated into a grey marlstone succession. Previous studies documented the benthic foraminifera extinction event (BEE) in this claystone. Now biodeformational structures and trace fossils were investigated in this interval to evaluate the impact of the extinction event on the macrobenthic tracemaker fauna. Using the stratigraphic distribution pattern of trace fossils, the lowermost Eocene claystone can be subdivided into three parts: (1) the lower part shows a trace fossil assemblage consisting of Chondrites isp., Planolites isp., Thalassinoides isp., and Zoophycos isp., (2) the middle part is characterized by primary sedimentary lamination and exceedingly rare ichnofossils, and (3) the upper part shows a less abundant and less diverse trace fossil assemblage than the lower part, indicating a slow recovery of the macrobenthic tracemaker community. This pattern demonstrates that macrobenthic communities were severely affected by the ecological perturbations in the earliest Eocene. The change in sediment colouration towards red colour in the middle part of the Paleocene–Eocene transition at the Untersberg section, together with decrease in bioturbation degree indicate that oxygen consumption was rather reduced during the PETM, and the loss in bioturbation is thus unrelated to oxygen limitation. Trace fossils can be used to improve the resolution of the benthic extinction interval and provide an excellent proxy for the precise determination of timing of the climax of this global event.
The Futoma Member (Oligocene, Rupelian) of the Menilite Formation is present only in the northern part of the Skole Nappe. Some diatomitic layers of this member in the Nowy Borek section contain coarse-grained detrital material composed of a variety of metamorphic, volcanic and sedimentary rock fragments. The material derives from primary and secondary sources. Most abundant are debris of metamorphic rocks, mostly gneisses and mica schists. The metamorphic origin of these rocks is confirmed by the composition of heavy mineral assemblages and garnet chemistry. These rocks could have been transported from a local source located close to the margin of the Skole Basin or within that basin. The volcanic rocks reflect Paleogene volcanic activity that was widespread in the Carpathian region. Cherts, which could have been subjected to synsedimentary erosion, may have been derived from the older portions of the same formation.
Mariusz Kędzierski, M. Adam Gasiński and Alfred Uchman
In the Gaj section (Polish Carpathians, Skole Nappe, Ropianka Formation), the Late Maastrichtian calcareous nannofossil biostratigraphy is compared with foraminiferal zonation based on the occurrence of the planktonic foraminiferid index species Abathomphalus mayaroensis. It appears that the LO of A. mayaroensis, which has been used previously in the studied section as the possible K/Pg boundary indicator is located below the boundary. The disappearance of A. mayaroensis along with other planktonic foraminiferids before the Cretaceous–Paleogene (K/Pg) boundary mass extinction event may be a consequence of the Late Maastrichtian rapid warming pulses. Moreover, the Paleogene age cannot be supported by the FO of the benthic foraminiferid Rzehakina fissistomata, because it first appears together with the nannofossil Ceratolithoides kamptneri (zonal marker for the latest Maastrichtian UC20cTP Zone). According to the present study, the whole studied section represents the lower Upper to the upper Upper Maastrichtian UC20bTP and UC20cTP nannofossil zones, so that it corresponds to the lower-middle part of the planktonic foraminiferal A. mayaroensis Zone, which, according to the scheme by Caron (1985), should extend up to the K/Pg boundary.