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

Abstract

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.