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Wenlock (Silurian) graptolitic shales from the Kocaeli Peninsula (Derince-Izmit), NW Turkey

Sachanski V., Goncuoglu M., Gedik I.

Acta Geologica Polonica

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2008

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Vol. 58, no. 4

387-393

EN

Alternating dark grey to black thin-bedded limestones and yellowish-grey calcareous shales in a recently discovered section in Izmit (Derince), eastern Kocaeli Peninsula, yielded graptolites of the middle part of the Wenlock - Cyrtograptus lundgreni Zone and possibly Upper Cy. rigidus-Cy. perneri Zone. This is the first record of graptolitic shale facies rocks in the Kocaeli Peninsula. The succession described is more akin to the Silurian of the Zonguldak Terrane than the shallow-marine carbonate facies of the Istanbul Terrane. It is therefore suggested that the contact between the Istanbul and Zonguldak terranes should be located to the west of Izmit (Derince).

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A new high-resolution chitinozoan composite standard for the East Baltic Lower Silurian succession based on numerical analysis

Rubel M., Nestor V., Harris M.T., Sheehan P.M., Ainsaar L., Männik P., Nölvak J.

Geological Quarterly

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2006

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Vol. 50, No. 3

323-332

EN

The chitinozoan successions (zonation) in the Llandovery and Wenlock deposits, accumulated along the northern shelf edge of the Livonian Basin, an embayment of the Palaeobaltic sea, is studied and used for time-rock correlation of the area. Analysis of the ranges of 180 taxa from 44 sections (41 of them well-sections) by graphic correlation revealed largely compatible successions of taxa as well as local stratigraphic gaps in both shelf and basin sections. Alternatives to graphic methods also produced composite standards based on stratigraphic relationships (below, co-occurring, or above) of taxonomic ranges and considered as palaeontological time scales (composites) similar to zonal schemes. We constructed such a scale using the DISTR algorithm to analyse the distribution of 84 taxa and recognized 41 datum planes. This scale includes the traditional regional and global chitinozoan zones and the associated chronological standards (including regional stages). The BioGraph and DISTR algorithms were used to study diversity changes, and to illustrate patterns of originations and extinctions of the chitinozoans. Correlation plots between composite standard and particular sections reveal variations in sedimentary rock accumulation patterns, supporting the results of sequence stratigraphic analysis of the study interval.

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Abnormalities in the development of monograptid colonies

Teller L.

Kwartalnik Geologiczny

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1999

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Vol. 43, Nr 3

347-352

EN

Examples of abnormalities and regeneration in Wenlock Monograptidae are described and illustrated. The sicula displays deformations of the dorsal processes, swellings of virgula or extremely numerous internal rings. Some thecae reveal deformed apertures various excrescences and shortenings. Excessive growth and reduction of lateral apertures are very common. Specimens with split of virgulae have also been found. These phenomena seem to be common among graptolites but their origin is not very clear, each case requiring a separate interpretation. The only exception is regeneration whose mechanism is the best studied so far.

PL

Przytoczono i omówiono nieprawidłowości w rozwoju astogenetycznym u wenlockich kolonii graptolitów. W obrębie sikuli stwierdzono deformacje wyrostków dorsalnych, zgrubienia na wirgelli oraz liczne pierścienie sikularne. Niektóre teki wykazują deformacje apertur, krótsze lub nienormalnie długie wyrostki aperturalne, a także narośla, które stanowią najprawdopodobniej przytwierdzone chitinozoa. Napotkano także kolonie z rozdwajająca się wirgulą oraz kolonie zregenerowane po uprzednim uszkodzeniu. Zaobserwowane zjawiska wydają się być częste wśród kolonii graptolitów, a obserwować można je łatwiej na materiale wyizolowanym chemicznie ze skały. Przebadany materiał pochodzi z profilu wenloku otworu Zawada 1(NE Polska).