Małgorzata Gonera

Palaeoclimatic interpretation based on Middle Miocene planktonic Foraminifera: the Silesia Basin (Paratethys) and Monferrato (Tethys) records

A comparative study of the distribution and palaeoclimatic interpretation of temperature-related taxa of Middle Miocene planktonic foraminifera from the Paratethys Silesia Basin (southern Poland) and Tethys Monferrato area (northwestern Italy) is presented. The time span considered (Badenian–Langhian/Serravallian) is the last period of significant connection between the Paratethys and Mediterranean Tethys, even though the depositional conditions, water circulation and connection with the oceanic realm were not always favourable to the life and preservation of significant planktonic foraminiferal taxa. The Silesia Basin, located in the western segment of the Karpathian Foredeep, is filled by an autochthonous, non-folded cover of Miocene deposits. Four stratigraphic sections were studied in this area, characterised by Carpathian sandy deposits of the Klodnica Formation, Lower Badenian unbedded marly clays, marls and strongly bedded Lithothamnium marls (Skawina Formation), Middle Badenian anhydrite and laminated clay shales (Krzyźanowice Formation), Upper Badenian unbedded marly clays, followed by fine-grained sands, sandy limestone layers, and bioclastic levels rich in molluscs and calcareous algae (Gliwice Formation). The Monferrato area corresponds to the northwestern termination of the Apennines thrust belt and consists of an Eocene–Miocene mainly terrigenous succession, resting unconformably on Upper Cretaceous and Eocene Ligurian flysch. Three stratigraphic sections are studied in the eastern area, characterised by Late Oligocene to Early Burdigalian deepwater terrigenous sediments (Marne di Antognola Formation), followed unconformably by Early to Middle Miocene carbonate sediments, originating in a foramol platform depositional environment (Pietra da Cantoni Group), and by grey–whitish glauconitic marls of the Marne di Mincengo Formation (Late Langhian–Serravallian). Twenty-three species of Tethys and Paratethys planktonic foraminifera were grouped in cold (Globigerina bulloides, Globigerina quinqueloba, Globigerina praebulloides gr., Globorotaloides spp., Catapsydrax spp.), cold–temperate (Zeaglobigerina woodi, Z. brazieri Globorotalia scitula gr., Globorotalia bykovae), warm (Globigerinoides spp., orbuliniforms, including Praeorbulina spp. and Orbulina spp., Globigerina ciperoensis, Dentoglobigerina altispira gr., Velapertina indigena, Globorotalia praemenardii), and warm–temperate indices (Paragloborotalia siakensis gr., Dentoglobigerina baroemoenensis gr., Globoquadrina praedehiscens and G. dehiscens, Tenuitellinata angustiumbilicata, Globigerinella obesa, Globigerina venezuelana). Their relative abundance was used to reconstruct palaeoclimatic curves. Comparison of the palaeoclimatic curves makes it possible to recognise a climatic change from warmer conditions in the Langhian towards relatively colder conditions in the Serravallian. The fall in warm-related taxa was much more pronounced in the Silesia Basin than in the Monferrato area. This palaeoclimatic evidence may be interpreted as the beginning of a series of oscillations pointing to a period of cooling, corresponding to one of the major global changes in the palaeoclimatic/palaeoceanographic history of the Cenozoic, i.e. the ‘Mid-Miocene event’, Mi3 [Miller et al. (1991) Paleoceanography 6, 33–52].

Natural and historic heritage of the Bochnia Salt Mine (South Poland)

The Bochnia Salt Mine, presented in this paper, is situated ca. 40 km E of Cracow, in the southern part of the Neogene Carpathian Foredeep, close to the Carpathian edge. In this region the rock-salt deposits formed as a result of the Late Miocene folding and local tectonic thickening of Badenian evaporites. The Bochnia deposit, situated in the almost vertical N limb of the Bochnia Anticline, stretches ca. 7 km WE, but only 15-200 m NS. Salt mining in Bochnia began in the thirteenth c. and continued until 1990. The historic part of the mine, since 1995 operated by a company supplying health and tourism services, is an officially listed monument of historic heritage. Legal protection also comprises 27 sites of key value for the geology of the deposit. These documentation sites record the whole profile of the evaporite series and the adjacent beds, main and minor tectonic structures, as well as mineralogical curiosities, such as fibrous halite and enterolithic anhydrite. For some years, efforts have been made to enter the Bochnia Salt Mine, in 2008 visited by over 140 000 tourists, on the UNESCO World List of Cultural and Natural Heritage.

Isotopic Events Preceding the Badenian Salinity Crisis in the Central Paratethys, Middle Miocene, Poland

Middle Miocene foraminifera from the Upper Silesian Basin (Poland) have been analysed. The stable oxygen and carbon isotope signatures in Uvigerina, Globigerina bulloides, and Globigerinoides quadrilobatus show a consistent tendency of directional changes. There is an abrupt, strong increase in the proportion of heavy isotopes of δ18O recorded about 10 m below the Badenian evaporites.

Coiling direction in Middle Miocene globorotaliids (Foraminiferida) – a case study in the Paratethys (Upper Silesia Basin, Poland)

The paper deals with sub-evaporite Badenian deposits (Middle Miocene, Paratethys) that display a sudden appearance of globorotaliid taxa showing preferences in the taxonomic set and coiling direction. An interval of sinistrally coiled Jenkinsella mayeri with proportionally coiled Globoconella bykovae is at the bottom of the studied sequence. It is followed by an interval of proportionally coiled Jenkinsella transsylvanica . Proportionally coiled Globoconella bykovae with a small number of proportionally coiled Jenkinsella transsylvanica are at the top of the Moravian (CPN 7) substage ( Orbulina suturalis alias Lagenidae Zone). The sub-evaporite part of the Wielician (CPN 8) substage ( Uvigerina costai alias Spiroplectammina Zone) began with a globorotaliid-barren interval (IIC biozone). It is followed by biozone IID displaying three globorotallid peaks amongst globorotallid-barren deposits. Only globoconellas are present in all these three events. Proportionally coiled Globoconella bykovae appeared first. It is followed by proportionally coiled Globoconella minoritesta and sinistrally coiled Globoconella bykovae at the end of the biozone IID. Coiling preferences of globorotaliids have been compared to changes in the hydrographic regime unfolding during the CPN 7 and CPN 8 in the studied area of the Paratethys. The study discovers that the coiling of globorotaliids responded selectively to the hydrographic changes. Globoconella bykovae is highly opportunistic and can tolerate considerable temperature changes. Specimens of this taxon persist to coil proportionally during the sub-evaporite Badenian, except for the shift to sinistral coiling just prior to the Wielician evaporites. Sinistrally coiled Jenkinsella mayeri is the most sensitive to hydrographic changes. This taxon retreated at the onset of the temperature drop during the mid-Moravian cryptic cooling. This cooling is marked by the new jenkinsellid occurrence – proportionally coiled Jenkinsella transsylvanica . Proportionally coiled Globoconella minoritesta is present in the middle of the IID globorotaliid peaks. The globorotaliid coiling data, presented in this paper, has been calibrated to the global stratigraphy. The integrated data (foraminifera, nannofossils, oxygen and carbon stable isotopes, radiometric measurements) supports the view that the CPN 7/CPN 8 boundary is coeval to the Langhian/Serravalian one. In the Polish part of the Carpathian Foredeep, the boundary runs within the Skawina Formation.