Sediments dynamics in a paratethys sea: Dacian Basin (Late Neogene, Romania)

Category Sedimentology
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Jipa, Dan Constantin
Holding Date 11 October 2008

Dacian Basin, a small, epicontinental brackish sea, was one of the late Neogene units of the Paratethys domain. The development of the basin and the dynamics of its sediments were significantly influenced by the basin location at the foot of the Carpathian Mountains, at a distance from the Balkan Mountains and in permanent connection with the Black Sea depression.
Sediments dynamics is investigated in relation with the three major development stages of the Dacian Basin: appearance, sediment filling and drying out of the basin.
Reacting to the simultaneous action of two Carpathian source-areas, at the beginning of the Dacian Basin existence (middle - upper Sarmatian s.l.) two separate sediment depo-centers developed. The same pattern continued during the Meotian time, with separate, but enlarged accumulation areas. This is the stage I (11 - 10 Ma till 5.9 Ma) of the Dacian Basin sediment filling evolution.
The lower Pontian sediment thickness distribution in the Dacian Basin indicates an important westward migration of the sediments. This is the beginning of the stage II (5.9 to 4.9 - 4.5 Ma) of the basin sediment filling. During this stage the sediment deficient area in between the two previously separated depo-centers was filled out. This action continued during the late Pontian and the lower Dacian time. The existence of a deep depression at the western end of the Dacian basin was a determinant factor for the along-basin, westward dominant migration of the sediments.
The first two sediment fill stages took place while the Dacian Basin functioned as a low salinity marine unit. Starting from the middle Dacian time the basin begun to dry out. The passage from the marine to the continental environment in the Dacian Basin area was rather slow (about 700 ky), continuing to the end of the Dacian time (4.07 Ma). During this phase the sediment dynamics changed, and the sediment migration front moved away from the Carpathians, the dominant supplier of clastic material.
The tectonic and climatic activities in the Carpathian area were the prevailing control factors for the sediment dynamics at the Dacian Basin scale. The existence of two independent Carpathian source-areas, located on one side of the basin, determined the initial pattern of the sediment migration. The large-scale basin morphology, strongly under tectonics control, determined the sedimentary dynamic behavior during the second sediment-filling stage. The third and final stage of the Dacian Basin evolution appears to have been under the influence of the sea-level variation in the Black Sea depression.