DACIAN BASIN - GeoEcoMar

10.2. Dacian Basin paleocurrent pattern
The marginal, shallow-water sediment transport pattern is an important and
better-known aspect of the detrital material transfer within Dacian Basin. The paleocurrent
flow directions in the sub-Carpathian marginal area (Fig. 10.4) reveal the
following main characters:
■ longitudinal paleocurrents, flowing southward along the basin axis, prevailed
in the northern part of the Dacian Basin, coexisting with transversal
currents (Fig. 10.4 A and B);
■ in the littoral area from the central and western Dacian Basin, the current
directions are largely dispersed, but they show a dominant component describing
a south-west current flow trend (Fig. 10.4 C, D and E).
These data indicate that the littoral paleocurrents have a tendency to turn and
flow toward the western end of the Dacian Basin (Fig. 10.9). The general, westward
dip of the trough axis was probably the factor that controlled the reversal of the
paleocurrents flow direction.
The flow direction along the trough axis is better observed in the northern part of
the Dacian Basin. This is evidenced by the dominant paleocurrent direction, but also by
the large scale transition observed in the area between Putna and Buzău Rivers, shown
by the grain size and current structures of the thick sand beds (see Chapter 6.1).
The gradual deepening of the Dacian Basin axial zone is supported by the long
term westward extension of the eastern depocenter (Fig. 10.1). The subsidence cannot
be invoked as a factor to explain the westward extension of the sediment accumulation
area. The extension took place from the high subsidence area in the north (Focşani-
Buzău zone; Bertotti et al., 2003) toward a less subsident zone in the west (Fig. 4.8).
If we accept that the westward deepening of the Dacian Basin influenced the
paleocurrents orientation in the littoral zone, it means that in the axial part of the
basin the paleocurrents are longitudinal, flowing toward the western end of the
Dacian Basin trough (Fig. 10.9). The dominantly longitudinal Dacian Basin sediment
transport result also from the successive Maeotian-Dacian patterns of the sediment
thickness (Fig. 9.1).
In the deepest part of the Dacian Basin, near its western end, the dominant
sediment transport is made by prograding sedimentary bodies with large scale
inclined surfaces (Figs 4.6 and 10.9). These structures probably appeared as a reaction
to the deepening in the western area of the Dacian Basin, combined with a
large sediment supply.
In conclusion, the sediment transport pattern of the brackish-marine Dacian
Basin includes three segments: (1) the transversal, turning longitudinal sub-Carpathian
littoral current system, (2) the longitudinal sediment transport in the axial
zone of the deepening trough and (3) the prograding system in the deepest western
end of the basin. The segments (1) and (3) of the sediment transport are based
on recorded data, but the segment (2) is entirely interpretative.
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