DACIAN BASIN - GeoEcoMar

1.2. Stratigraphy
gation method: direct observations in the sub-Carpathians, i.e., the proximal area,
and use of subsurface data in the outer, southern and eastern areas.
The Dacian Basin was a component of the large epicontinental sea named Paratethys
by Laskarev (1924). After its opening during the late Eocene time (34 Ma)
(Rusu, 1977; Baldi, 1979), Paratethys went through several major environmental
phases with specific conditions. The initial (Lower Oligocene) Paratethian phase of
decreased water salinity and endemism was replaced during Middle Oligocene by
prevailing open marine conditions, with dominant clastic sedimentation (Rögle,
1999). As a result of restricted internal communication, brackish water and endemic
fauna dominated the final Paratethys stage. Formed during this last stage (late
Sarmatian, s. l.), the Dacian Basin coexisted within the Paratethys with the Pannonian,
Euxinian and Caspian basins (Fig. 1.3).
1.2. STRATIgRAPHY
The Dacian Basin evolved during a period of time when Paratethys was represented by
distinct basins with restricted and variable communication between them. These basins
shared some common characteristics, including reduced water salinity, and were
dominated by clastic sedimentation. However, significant differences existed between
the Paratethian basins: these include basin size and physiography, the occurrence, development
and evolution of fauna and their respective environments, and others.
One essential distinction existing between the Paratethys basins came out of
the succession of the interconnections moments (leading to uni- or bi-directional,
selective faunal migrations) and moments of isolation and implicitly endemism.
Biostratigraphic markers which resulted from the successive connection and isolation
of these basins generated differing stratigraphic scales, making it difficult to
compare one Paratethys basin with the other.
1.2.1. Biostratigraphic scale 1
A Dacian Basin scale based on stratigraphic rules and paleontologic dating had to
rely on specific features of the basin and on characteristics shared with the neighboring
Paratethys basins. The initial stratigraphic scale based on paleoecological
and paleontologic analysis of the Dacian Basin was devised by Teisseyre (1907).
As a result of its paleogeographic setting (Fig. 1.3), the Dacian Basin developed
in rather close communication with the Euxinian Basin, while the relationships with
the Pannonian Basin have been more restricted. That is why the biostratigraphic
scale of the Dacian Basin includes several stages similar to the Euxinian Basin stages
(Table 1.1): Sarmatian sensu lato, Maeotian and Pontian.
1 Author: Radu Olteanu
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