Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Karpatian and Lower Badenian sediments on the locality Brus


Pavla Tomanová Petrová

Geoscience Research Reports 49, 2016, pages 171–176
Map sheets: Olomouc (24-22)

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Published online: 21 September 2016

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Foraminiferal assemblages were studied in the Miocene sediments in the Carpathian Foredeep from the borehole Brus 1 nearby Prostějov, Central Moravia (Fig. 1). Other fossils, such as fragments of the plates and spines of echinoids occur in the upper part of the profile (150-330 cm). Fragments of sponge spicules occur in the depth 580-1 350 cm, especially. Most of Teleostei teeth and otoliths were found in the depth 1 690-1 980 cm. Bivalves were observed in the whole profile occasionally. Bryozoans generally occur in the whole profile, they predominate in its upper part (150-750 cm). Analysis of foraminiferal assemblages was based on 15 samples from borehole Brus 1, using sample-wash residua and a NIKON binocular microscope. Palaeoecological interpretations were made according to Murray (2006), foraminiferal biostratigraphy was based on Cicha et al. (1998). Results of a systematic sampling of the core are presented in Table 1. Occurrence of planktonic foraminifers was rare (Fig. 2). Relatively numerous and diversified assemblages of coastal and shallow water foraminifers were documented in borehole Brus 1. Benthos taxa Hanzawaia boueana (Orb.), Asterigerinata planorbis (Orb.), Ammonia viennensis (Orb.), Porosononion granosum (Orb.) and of Elphidium div. sp. dominated. Locally foraminifers indicate marine paleoenvironment with unstable contents of oxygen and changing salinity. At the basis of the profile foraminiferal tests are usually more damaged. Asterigerinata planorbis (Orb.) and Hanzawaia boueana (Orb.) predominate at the central part of the borehole (450-1150 cm). In quantity, big foraminifers (Planostegina div. sp.) were documented at the depth interval 750-1150 cm. Assemblages of genera Hanzawaia-Asterigerinata-Lenticulina (750-850 cm) perhaps document mixing of shallow (warm) water and deeper (cold) water (Hladilová et al. 2014). At the top of the succession, numerous elphidias, which inhabit warm and shallow sea waters, were observed.
Based on sporadic occurrence of foraminifers Cassigerinella boudecensis Pok., Globigerina ottnangiensis Rögl, Pappina breviformis (Papp et Turn.) and ostracods Cytheridea paracuminata Koll., sediments in the depth 1150-1350 m were correlated with Karpatian-Lower Badenian boundary. This boundary is also associated with decrease of oxygen; it is indicated by more abundant occurrence of euryoxybiont foraminifers.