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Environmental conditions in a Carpathian deep sea basin during the period preceding Oceanic Anoxic Event 2 – a case study from the Skole Nappe

In: Geologica Carpathica, vol. 65, no. 6
Krzysztof Bak - Marta Bak - Zbigniew Górny - Anna Wolska

Details:

Year, pages: 2014, 433 - 450
Language: eng
Keywords:
Cenomanian Upper Cretaceous, Polish Outer Carpathians Skole Nappe, environment, Radiolaria, Foraminifera, sponge spicules, pellets
About article:
Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foraminifers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutrients to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degradation of the pellets during their fall to the sea floor.
How to cite:
ISO 690:
Bak, K., Bak, M., Górny, Z., Wolska, A. 2014. Environmental conditions in a Carpathian deep sea basin during the period preceding Oceanic Anoxic Event 2 – a case study from the Skole Nappe. In Geologica Carpathica, vol. 65, no.6, pp. 433-450. 1335-0552. DOI: https://doi.org/10.1515/geoca-2015-0004

APA:
Bak, K., Bak, M., Górny, Z., Wolska, A. (2014). Environmental conditions in a Carpathian deep sea basin during the period preceding Oceanic Anoxic Event 2 – a case study from the Skole Nappe. Geologica Carpathica, 65(6), 433-450. 1335-0552. DOI: https://doi.org/10.1515/geoca-2015-0004
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