Early to early Middle Ordovician conodont biostratigraphy of the Tamsalu drill core, central Estonia

Abstract: This investigation examines the distribution of conodont elements in the Early to early Middle Ordovician Latorpian, Volkhovian, Kundan and Aserian stages of the Tamsalu drill core in central Estonia. Slightly more than 24, 600 conodont elements from 17 samples were examined, and the biostratigraphic results were compared to previous works on conodont biostratigraphy from localities in Estonia, Russia and Öland, Sweden. The samples are indicative of the Oepikodus evae Zone, the Baltoniodus navis Zone, the Paroistodus originalis Zone, the Baltoniodus norrlandicus Zone, the Lenodus variabilis Zone, the Yangtzeplacognathus crassus Zone, the Eoplacognathus pseudoplanus Zone, (the latter including the Microzarkodina hagetiana and the Microzarkodina ozarkodella subzones) and finally the Eoplacognathus suecicus Zone. The thicknesses of the different stages (Latorpian, Volkhovian, Kundan and Aserian) are compared between the following localities in Estonia: Tamsalu, Kaugatuma, Ohesaare, Rumba, Kullamaa, Mäekalda, Tartu, Taga-Roostoja and Ontika. Two new species, Parapaltodus n. sp. A and Texania n. sp. A, are described.