Author	Rusu, A., Brotea, D., Ionescu, A., Nagymarosy, A. and Wanek, F.
Year	1993
Journal	Romanian Journal of Stratigraphy 75: 71-82
Title	Biostratigraphic study of the Eocene-Oligocene boundary in the type section of the Brebi Marls (Transylvania, Romania)

Abstract Rusu, A., Brotea, D., Ionescu, A., Nagymarosy, A. and Wanek, F., 1993; Biostratigraphic study of the Eocene-Oligocene boundary in the type section of the Brebi Marls (Transylvania, Romania). Romanian Journal of Stratigraphy 75: 71-82 The paperpresents the results of the researches on molluscs, ostracods, benthic foraminifers, calcareous nannoplankton and dinoflagellates from the type section of the Brebi Marls, considered as one of the most useful in the world for the study of the Eocene-Oligocene boundary. The malacologic assemblage is of Priabonian type in the whole section, the typically Oligocene species occurring in the suprajacent member. The changes in ostracod and benthic foraminifer faunas are gradual, without marking an obvious threshold in tracing the boundary. Two local zones of ostracods have been separated, the Sphaenocytherdea parvogracilis Zone and the Hazelina indigena Zone. The distribution of calcareous nannoplankton points to the presence of the NP 21 and NP 22 Zones, the Eocene-Oligocene boundary being placed in the first zone within he interval of the Ericsonia obruta acme. It corresponds to the boundary between the two ostracod zones. Dinoflagellates are referred to the Wetzeliella (Rhombodinium) perforatum Zone, the index form getting up in Transylvania to the top of the NP 21 Zone. The Brebi Marls were deposited at a depth corresponding to the outer shelf in normal marine waters. Transylvania was part of the Mesogcan Realm, but nannoplankton also indicates the influence of cool waters around the Eocene-Oligocene boundary.