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Microfacies, foraminifers and carbon and oxygen isotopes in a basinal section of the Zechstein Limestone (Wuchiapingian): Bonikowo 2 borehole, western Poland

Peryt D., Peryt T. M., Hałas S., Raczyński P.

Geological Quarterly

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2016

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Vol. 60, No. 4

827--839

EN

The Zechstein Limestone of the Bonikowo 2 borehole is composed of limestone with varied dolomite content and is slightly thicker (3.4 m) than other supposed condensed sections in SW Poland. The microfacies (mostly bioclastic wackestones-packstones) are characteristic of open marine limestone deposited in deep shelf environments. The common occurrence of echinoids in all parts of the section, except close to its top, indicates no essential change in sea water salinity. However, the palaeotemperature interpretation of the highest δ18O value of calcite recorded in the Bonikowo 2 borehole (+0.32‰) indicates a temperature of 22.9°C when a δ18O of water = 2‰ is assumed. The δ13C and δ18O curves for calcite and dolomite are similar in shape, and their mean values are similar: +1.8 ±1.5‰ for calcite, respectively, and +1.9 ±2.3‰ and –4.3 ±2.4‰, –3.8 ±4.3‰ for dolomite. There is a recrystallized interval in the lower part of the section with both δ13C and δ18O values reduced. This may be regarded as an aerobic equivalent of the Kupferschiefer. The diversity and abundance of foraminifers is significant throughout the section studied; lagenids prevail, and this is considered to be due to the dysaerobic conditions throughout the duration of deposition of the Zechstein Limestone.

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Foraminiferal record of the Middle Miocene climate transition prior to the Badenian salinity crisis in the Polish Carpathian Foredeep Basin (Central Paratethys)

Peryt D.

Geological Quarterly

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2013

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Vol. 57, No. 1

141–-164

EN

Foraminifers occurring in marls underlying the Middle Miocene Badenian gypsum in the northern Polish Carpathian Foredeep in one borehole section [Młyny (Busko) PIG 1] and in two dewatering pits in operating quarries (Leszcze and Borków) contain well-preserved foraminifers. Sixty-seven species of benthic and twenty-one species of planktonic foraminifers are recorded in the 12-m-thick section of the Młyny borehole. Benthic assemblages are characterized by the dominance of Bulimina and Uvigerina while planktonic assemblages are composed mainly by warm-water orbulinids and Globigerinoides spp. in the lower part of the Młyny section and by temperate-cold water Globigerina spp. in the upper part of the Młyny section as well as the Leszcze and Borków sections. The taxonomic composition of foraminiferal assemblages makes it possible to distinguish two foraminiferal zones in the Młyny borehole: the Orbulina suturalis and Uvigerina costai zones, and only the latter zone is accessible at Leszcze and Borków. The benthic foraminiferal successions in the studied interval suggest oxygenation and productivity changes in the Carpathian Foredeep Basin prior to the Badenian salinity crisis. Four intervals of lowered oxygenation and/or elevated organic flux to the sea-floor are recognized; the intervals in which foraminiferal assemblages suggest marine environments with lowered oxygenation in bottom waters alternate between the intervals where stress markers form less than 50% of the benthic foraminiferal assemblages. Benthic assemblages are moderately to highly diversified, and species have more equal frequencies. The upsection decrease in the proportion of planktonic foraminifers reflects the shallowing of the basin accompanied by a decrease in the temperature gradient between the upper (warmer) and deeper (colder) water beds. The average palaeotemperature of water based on d18O of Uvigerina and Globigerina decreased by ca. 2 and ca. 6°C, respectively (from 9.9 and 17.4°C in the Orbulina suturalis Zone to 7.9 and 11.5°C in the Uvigerina costai Zone, respectively). Below the gypsum, the d18O values of both benthic and planktonic foraminifers show quite large variations possibly due to the salinity increase. Coeval domination of benthic foraminiferal assemblages by Bulimina suggests increased surface water productivity and an increased organic flux to the sea-floor prior to the onset of evaporite deposition and/or salinity increase.

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Inoceramid and foraminiferal record and biozonation of the Turonian and Coniacian (Upper Cretaceous) of the Mangyshlak Mts., western Kazakhstan

Walaszczyk I., Kopaevich L. F., Beniamovski V. N.

Acta Geologica Polonica

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2013

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Vol. 63, no. 4

469--487

EN

The Turonian and Coniacian (Upper Cretaceous) of the Mangyshlak Mts., western Kazakhstan, yielded a rich and relatively complete inoceramid bivalve record. The faunas and their succession correspond to those known from central and eastern Europe, allowing the zonation established in the latter areas to be applied in a virtually identical form. The gaps in the record of the group in Mangyshlak stem from the regional hiatuses in the geological record in the area and do not reflect any biogeographical differences between eastern and central-western Europe. Planktonic foraminifera are rare. Four successive interval range zones can be distinguished: in ascending stratigraphic order, the Helvetoglobotrunaca helvetica, Marginotruncaca pseudolinneiana, Marginotruncana coronata, and Concavotruncana concavata zones. Their correlation with the inoceramid zonation and, consequently, with the chronostratigraphic scheme, is demonstrated. The zonation and chronostratigraphic subdivision as applied in Mangyshlak may easily be applied to other areas of the peri-Caspian region (Caucasus, Tuarkyr, Kopet-Dagh, SE margin of the East-European Craton).