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New data on the age and stratigraphic relationships of the Czajakowa Radiolarite Formation in the Pieniny Klippen Belt (Carpathians) based on the radiolarian biostratigraphy in the stratotype section

Bąk M., Chodacka S., Bąk K., Okoński S.

Acta Geologica Polonica

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2018

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Vol. 68, no. 1

1--20

EN

The radiolarian biostratigraphy of the Middle–Upper Jurassic pelagic siliceous sediments (Czajakowa Radiolarite Formation) in the Niedzica succession of the Pieniny Klippen Belt (Carpathians) is interpreted in terms of their age in a stratotype section, and facies equivalents in other tectonic-facies units of this region. The siliceous sediments are represented by radiolarian cherts and silicified limestones which are underlain and overlain by red nodular limestones, equivalents of the Rosso Ammonitico facies. The radiolarian association includes thirty-seven taxa belonging to twenty one genera which represent the Northern Tethyan Palaeogeographic Province. Key radiolarians recorded provide a means of correlation with zonation schemes based on Unitary Associations defined for the Jurassic Tethyan sediments. The age of the Czajakowa Radiolarite Formation in the stratotype section is determined as U.A.Z.9 to U.A.Z.11 corresponding to middle Oxfordian up to Kimmeridgian. Comparison of radiolarian biozones from the stratotype section with other facial equivalent sections in the Pieniny Klippen Belt reveals a significant diachronism for both the lower and the upper limits of the Jurassic pelagic siliceous facies.

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Unconformity surfaces in pelagic carbonate environments : A case from the Middle Bathonian of the Betic Cordillera, SE Spain

Nieto L. M., Rodríguez-Tovar F. J., Molina J. M., Reolid M., Ruiz-Ortiz P. A.

Annales Societatis Geologorum Poloniae

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2014

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Vol. 84, No. 3

281--295

EN

Integrative studies of sedimentary and palaeontological topics for unconformity surfaces are useful in basin analysis. A middle Bathonian unconformity surface in the Ammonitico Rosso facies cropping out in the La Mola Unit (Subbetic Domain, Betic External Zone) was studied by integrating ichnological, palaeotectonic, and sedimentological analyses to decipher sea-level, tectonic, and palaeogeographic conditions during its development. The trace-fossil assemblage mainly consists of the Glossifungites (Thalassinoides, Arenicolites, and Gastrochaenolites) and Trypanites ichnofacies elements. Probable Ophiomorpha represents previous softground stages, Thalassinoides and Arenicolites were formed in firmground, Gastrochaenolites reflects an evolved firmground or early hardground, and Trypanites can be attributed to an incipient hardground. The degree of firmness, relative sea-level position, and continuity of deposition were related. The softground stage corresponds to a fall in relative sea level and continued deposition. The firmground (semi-consolidated substrate) probably reflects an extremely low sea level characterized by non-deposition, whereas the incipient hardground stage indicates an initial phase of relative sea-level rise, with an increase in marine current energy. The presence of two neptunian dyke systems reflects significant tectonic activity related to the transtensional deformation that affected the South Iberian Palaeomargin. Lateral variations in sedimentological and ichnological features recorded at similar discontinuity surfaces in nearby areas were considered and related to differences in bottom topography, with associated changes in sedimentation, and to the variable duration of the hiatus.

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Molluscan immigrations via biogeographical ecotone of the Middle Russian Sea during the Jurassic

Rogov M., Zakharov V., Kiselev D.

Volumina Jurassica

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2008

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Vol. 6, no. 1

143-152

EN

Patterns of molluscan immigration via the biogeographical ecotone zone of the Middle Russian Sea during the Middle – Late Jurassic have been studied in detail. Firstly, the migration routes and ranges of recent molluscs are briefly reviewed, with some comments about their applicability to the Jurassic. Secondly, the migrational events have been classified by their direction, duration and intensivity. We recognize two main types of immigration by their direction (unidirectional and multidirectional) and by their intensity (mass immigrations and isolated strayings). Recent progress in infrazonal ammonite biostratigraphy leads us to the more precise recognition of paleobiogeographical events and to the understanding of the immigration patterns that can produce more precise correlations.