Lower and Middle Ordovician conodonts from the subsurface of SE Estonia and adjacent Russia/Alam- ja Kesk-Ordoviitsiumi konodondid Kagu-Eesti puuraukudes

The distribution of conodonts in the Lower-Middle Ordovician beds was studied in five drill core sections of southeastern Estonia. Ten conodont zones and six subzones, from the Paroistodus proteus Zone to the Eoplacognathus lindstroemi Subzone, were established. The peculiarity of the studied sequen...

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Bibliographic Details
Published in:Estonian journal of earth sciences 2011-03, Vol.60 (1), p.1
Main Author: Viira, Viive
Format: Article
Language:English
Subjects:
Conodonts
Geochronology
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Summary:The distribution of conodonts in the Lower-Middle Ordovician beds was studied in five drill core sections of southeastern Estonia. Ten conodont zones and six subzones, from the Paroistodus proteus Zone to the Eoplacognathus lindstroemi Subzone, were established. The peculiarity of the studied sequence is that the Volkhov Stage is notably poor in conodonts, in particular Baltoniodus species. Large specimens of Drepanodus arcuatus and Protopanderodus rectus, however, are found in great numbers in the uppermost Volkhov and lower Kunda stages. The deeper shelf conodont faunas recognized in SE Estonia (Central Baltoscandian confacies belt) are compared with shallow shelf faunas of northern Estonia (North Estonian confacies belt). Key words: conodonts, biostratigraphy, Lower Ordovician, Middle Ordovician, Estonia. On uuritud konodontide levikut Alam- ja Kesk-Ordoviitsiumi kihtides viies Kagu-Eesti puuraugu labiloikes. On kindlaks tehtud kumme konodondi tsooni ja kuus alamtsooni, alates Paroistodus proteus'e tsoonist kuni Eoplacognathus lindstroemi alamtsoonini. Uldiselt on kindlakstehtud konodondi fauna sarnane Pohja-Eesti samaealisele faunale. Erinevus on Volhovi lademes, mis sisaldab markimisvaarselt vahe konodonte, eriti Baltoniodus'e liike. Kuid Drepanodus arcuatus'e ja Protopanderodus rectus'e suuri eksemplare on arvukalt leitud Ulem-Volhovi ning AlamKunda lademe setetes. Uldiselt on Kagu-Eesti sugava selfi konodondi kooslused vorreldud Pohja-Eesti madala selfi kooslustega.
ISSN:1736-4728
DOI:10.3176/earth.2011.1.01