DACIAN BASIN - GeoEcoMar

1.5. Overview of the Dacian Basin cyclic development
The Eastern and Southern Carpathians tectonic activity culminated during the
Sarmatian time (approximately 11 Ma), with subduction and continental collision
between the East European-Scythian-Moesian foreland and the inner Carpathians
Tisza-Dacia unit (Balla, 1986; Csontos, Vörös, 2004; Schmid et al., 2008). The Middle-Late
Sarmatian (sensu Eastern Paratethys, see Vasiliev, 2006) is the moment when the Subcarpathian
Nappe was thrust on top of the sedimentary cover of the foreland platforms
(Săndulescu, 1988; Maţenco, Bertotti, 2000). This event followed the Early and Middle
Miocene nappe stacking, which led to the emplacement of the Internal Moldavides.
The latest Miocene-Quaternary post-collisional evolution also involved some limited
deformation. The late orogenic evolution of the external part of the Romanian
Carpathians and their foreland began after the Middle Sarmatian cessation of the
major shortening (Leever et al., 2006), with a period of subsidence (Latest Miocene
- Pliocene). Focşani Depression, located in the northern Dacian Basin, was the site
of the highest subsidence values. The classically defined Wallachian compressional
stage recorded in the SE Carpathians (e.g., Hippolite and Săndulescu, 1996) has been
more recently quantified to 5 km of total shortening taking place along high-angle
reverse faults cross-cutting the already locked nappes contacts (e.g., Leever et al.,
2006). As a result, rapid exhumation took place in the Moldavides, being associated
with continued subsidence in the Focşani foreland (e.g., Maţenco et al., 2007).
The post-collision foreland of the Romanian Carpathians is paleogeographically
known as the Dacian Basin (e.g., Jipa, 2006 and references therein). Hence, the Quaternary
uplift led to the erosional removal of a large part of the proximal Focşani
foredeep.
Initially (Late Sarmatian s. l.), the Dacian Basin sedimentation was restricted
mostly to the pre-existent foredeep area. During its subsequent development (especially
during the Pontian time), the Dacian Basin sedimentation area extended
southward, over the northern part of the Moesian Platform and a part of the Scythian
platform (Fig. 1.7).
1.5. OvERvIEw OF THE DACIAN BASIN CYCLIC DEvELOPMENT
Three cycles of sedimentary and biological nature occurred during the development
of the Dacian Basin (Jipa, Olteanu, 2006). The cyclic evolution is evident in
the central and western part of the basin, where sedimentary sequences show
contrasting lithology, from clay to sand and gravel.
The lithofacial, paleoenvironmental and paleontological data suggest the existence
of the following development cycles:
■ cycle 1, Sarmatian ( s.l.);
■ cycle 2, Maeotian;
■
cycle 3, Pontian-Dacian-Romanian.
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