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Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume
Biostratigraphy and paleoenvironments of the Eocene deep water deposits from
the northern part of the Eastern Carpathians, Romania
Raluca BINDIU 1 , Ramona BĂLC 2 and Sorin FILIPESCU 1
1 Babeş-Bolyai University, Faculty of Biology and Geology, Department of Geology, 1 Mihail
Kogălniceanu Street, 400084 Cluj-Napoca, Romania
2 Babeş-Bolyai University, Faculty of Environmental Sciences and Engineering, 30 Fantanele Street,
400294 Cluj-Napoca, Romania
e-mail: bindiuraluca@gmail.com
Foraminifera and calcareous nannoplankton have been used to establish the age and the
paleoecology for a representative section located in the Suceava Valley near Brodina (N
47.87150°, E 25.39642°). The studied deposits belong to the northern part of the Tarcău
Nappe, Plopu Unit (Eastern Carpathians) and are represented by a mid- to distal fan turbiditic
succession. The age of the Plopu Unit has been a controversial discussion for a long time.
Based on the foraminiferal and calcareous nannoplankon assemblages some authors (Juravle,
2007; a.o.) consider that the age of this unit is Late Eocene, while others (Sandulescu, 1987;
a.o.) place the Middle/Late Eocene boundary within this unit. The Suceava Valley section is
characterized by rich agglutinated foraminifera and calcareous nannoplankton assemblages,
representing an ideal setting to restore the main bioevents and the paleoenvironmental
parameters. The corresponding period of the characteristic assemblages usually corresponds
to the maximum abundance or to local stratigraphic range of one or more species that
characterize each assemblage. Thus, the presence of index taxa Orbulinoides beckmani in the
basal part of the section permits the assignment of these deposits to middle Eocene age; for
the upper part of the section the FO and a brief maximum in the relative abundance of
Spiroplectammina spectabilis and Reticulophragmium amplectens is observed, indicating a
late Eocene age (Kaminski, 2005). The calcareous nannofossils (LO of Chiasmolithus solitus,
LO of Chiasmolitus oamaruensis and FO of Istmolithus recurvus) confirm that the studied
section falls in the NP15-NP19 biozone (Martini, 1971) which corresponds with NNTe8-
NNTe12 (Varol, 1998). Thus, we affirm that the boundary between the Middle and Late
Eocene is located within the the Plopu Unit.
The foraminifera diversity (Hurlbert, 1971), distribution of the agglutinated
morphogroups (Setoyama et al., 2011), and CaCO3 content display a positive correlation
throughout the studied section and suggest hydrodynamic and/or tectonic instability. Thus, the
occurrences of the calcareous benthic forms are correlated with variations of the CaCO3
content and suggest oscillations of the CCD. The instability of the paleoenvironmental
conditions, as shown by the variation in the organic matter flux (changes in the percentages of
M1 and M4b morphogroups along the studied section), can be caused by changes in the
direction of the bottom currents. These fluctuations are very similar to those described by
Oberhansli et al. (1991) for the Middle Eocene in the Atlantic Ocean, strengthening the
similarity between the Eocene paleoenvironment of the Eastern Carpathians and the Atlantic
basin.
Calcareous benthic foraminifera (Dentalina, Nodosaria, Stillostomella) are rare in
almost all samples, suggesting a possible transport from the shelf; planktonic foraminifera
(Globigerina, Globorotalia, Subbotina, Orbulinoides) are usually poorly preserved and were
identified only in the Middle Eocene. The calcareous nannoplankton assemblage is dominated
by the species belonging to the Noelaerhabdaceae (Reticulofenestra dictyoda, R. bisecta, R.
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