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Guettardiscyphia zitti sp. n. - a remarkable hexactinellid sponge from the Lower Turonian of the Bohemian Cretaceous Basin

Vodrážka R.

Geological Quarterly

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2017

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Vol. 61, No. 3

632--640

EN

This paper describes a new hexactinosidan hexactinellid Guettardiscyphia zitti sp. n. on the basis of a detailed study of 279 specimens from 12 localities in the southern part of the Bohemian Cretaceous Basin. All the studied material comes from the basal Bílá Hora Formation (Lower Turonian). The geology and palaeontology of the sponge-bearing strata at studied locations exhibit identical palaeoenvironmental settings: 1 - transgressive character of sediments with low sedimentation rates, 2 - presence of submarine swells formed by crystalline basement, 3 - hemipelagic sedimentation below the storm-wave base, and 4 - the presence of proliferating diverse sponge faunas with subordinate accompanying macrofaunal remains.

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Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

Schneider S., Jäger M., Kroh A., Mitterer A., Niebuhr B., Vodrážka R., Wilmsen M., Wood C. J., Zágoršek K.

Acta Geologica Polonica

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2013

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Vol. 63, no. 4

555--610

EN

With approximately 100 species, the invertebrate macrofauna of the Neuburg Kieselerde Member of the Wellheim Formation (Bavaria, southern Germany) is probably the most diverse fossil assemblage of the Danubian Cretaceous Group. Occurring as erosional relicts in post-depositional karst depressions, both the Cretaceous sediments and fossils have been silicified during diagenesis. The Neuburg Kieselerde Member, safely dated as Early Cenomanian to Early Turonian based on inoceramid bivalve biostratigraphy and sequence stratigraphy, preserves a predominantly soft-bottom community, which, however, is biased due to near-complete early diagenetic loss of aragonitic shells. The community is dominated by epifaunal and semi-infaunal bivalves as well as sponges that settled on various (bio-) clasts, and may widely be split into an early bivalve-echinoid assemblage and a succeeding sponge-brachiopod assemblage. In addition to these groups we document ichnofauna, polychaete tubes, nautilids and bryozoans. The fauna provides evidence of a shallow to moderately deep, calm, fully marine environment, which is interpreted as a largescale embayment herein. The fauna of the Neuburg Kieselerde Member is regarded as an important archive of lower Upper Cretaceous sea-life in the surroundings of the Mid-European Island.

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Calcareous nannofossils from the Upper Cretaceous of northern James Ross Island, Antarctica : a pilot study

Švábenická L., Vodrážka R., Nývlt D.

Geological Quarterly

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2012

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Vol. 56, No. 4

765--772

EN

The Czech scientific expedition to northern James Ross Island, Antarctica has tested the use of calcareous nannofossils as a possible tool for stratigraphic correlation of Cretaceous and Neogene strata. Only a few samples with poor nannofossil content gave useful information for biostratigraphy. The Lower Campanian Chiastozygus garrisonii Zone and Gephyrobiscutum diabolum Subzone, respectively, was established in the lower part of the Santa Marta Formation, Lachman Crags Member, from the common occurrence of Gephyrobiscutum diabolum associated with Broinsonia parca parca and Acuturris scotus. Deposits of the Late Miocene Mendel Formation yielded exclusively reworked nannofossils from the older Upper Cretaceous deposits. Nannofossils indicate at least two distinct stratigraphic levels: Middle Coniacian and Santonian–basal Campanian, and these must have been sourced from the immediate area. The majority of the marine deposit samples studied were barren of nannofossils, probably due to late diagenetic secondary decalcification.