DACIAN BASIN - GeoEcoMar

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Chapter 12. From Brackish-Marine to Continental-Fluvial Depositional Environment
During the second development period (Middle Dacian to Romanian), the Dacian
Basin functioned as a continental area, with fluvial sedimentation. The continental-fluvial
development period of the Dacian Basin established a sharp environmental
distinction between the fluvial Dacian area and the brackish Euxinian
area. During the Dacian-Romanian fluvial stage the Danube paleo-river came into
existence in the Dacian Basin (not earlier than 4.5 Ma time) (Fig. 12.3). With the
Danubian sediment discharge on the western Euxinian shelf, direct and intensive
relationships were established for the first time between the Dacian Basin and the
Euxinian Basin.
12.2.2. Brackish Euxinian influxes into the fluvial Dacian Basin area
Sediments with brackish fauna are sometimes interbedded with fluvial Late
Pliocene (Romanian, approx. 4 - 1.6 Ma) deposits of the Dacian Basin (Liteanu et al.,
1968; Andreescu, 1972). The current interpretation of this evidence is that intermittently
the eastern area of the fluvial Dacian Basin was transgressed with marine water,
from the Euxinian Basin (Fig. 12.3). During these Euxinian transgressions brackish
fauna and normal marine flora were brought into the Dacian Basin territory.
Presently there is no data confirming the sediment supply connected with the
Euxinian brackish transgressions that took place in the Dacian Basin area during
the Romanian time. The question is if large amounts of sediment have been introduced
into the Dacian Basin area. If so, the sediment influx should have generated
a large deltaic structure. It is probably more realistic to believe that the influx consisted
mostly of brackish water, without a significant supply of sediment.
12.2.3. The Dacian Basin between the Carpathians and the Black Sea shelf
The Carpathian Mountains acted as a source of clastic sediment which promoted
the development of the Dacian Basin. But how much of the Carpathian-derived
clastics reached the Black Sea Depression? The problem of the detrital material
exchange between the Dacian Basin and the Euxinian Basin, during the Middle
Sarmatian – Romanian time (approx. 11 – 1.6 Ma), was investigated on the bases of
the information offered by published paleogeographic - lithofacies maps and the
data resulting from the sedimentogenetic study of the Dacian Basin.
The Dacian Basin was one of the brackish–marine units of the Paratethys epicontinental
sea (Fig. 12.1). This small basin was in the western neighbor of the large
Euxinian Basin, which included the Black Sea Depression and its shelf area. Dacian
and Euxinian basins were always in direct communication, as the faunal assemblages
indicate. But the important facies differences show that during its brackishmarine
existence the Dacian Basin was a different sedimentary province and had
no sediment exchanges with the Euxinian Basin.