Pecularities of the lithology and fauna of the early Katian (Ordovician) in the Lithuanian facies zone

The lithology and fauna on the south-eastern slope of the Middle Lithuanian Depression within the  Lithuanian facies zone (belt) is discussed in the  present paper. The study material consists of core from two deep drill-holes: Taučionys-49 and Drūkšiai-6 (Kazimirovo). As a result Drūkšiai, Dysna, Jakšiai, Paekna and Kaimynai formations from the  Oandu and Nabala regional stages have been distinguished in the  studied lithostratigraphy. The  biostratigraphy of described formations is based on the  description of brachiopods, trilobites and ostracodes. A stratigraphic gap distinguished in the Estonian Oandu Regional Stage in the stratotype section is completed by the continuous parastratotypic section of the Lithuanian Pajavonys-13 well. It is shown that the attribution by Sidaravičienė (1996) of Paekna, Kaimynai, and Dobilynė formations in the  Drūkšiai area to the Vormsi Regional Stage should be corrected. Only the Dobilynė Regional Stage should be left in this regional stage. The study presents new correlation between Middle Lithuanian and Livonian facies (belt) zones. The Drūkšiai–Paekna and the  Kaimynai formations are respectively correlated with the clingani and linearis graptolite zones. A  new species of brachiopods  – Thaerodonta notabile Pašk. sp. nov. – is described.