DACIAN BASIN - GeoEcoMar

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Chapter 5. Littoral Sedimentary Environment in the Dacian Basin
Presently no specific sedimentation depth can be assigned to the sedimentary
sequence cropping out along the Olteţ River. The only depth range which can be
argued is the accumulation environment bellow the base of the fair-weather wave
and storm action.
5.5.2. Littoral clay deposits: offshore or sediment-starved facies
Clay deposits are quantitatively dominant in the cropping out littoral sediment
sequences from the central and western part of the Dacian Basin. Usually, these
sediments have frequent intercalation of sand, mostly fine-grained. In the Bădislava
River geological section, there are clay intervals, several tens of meters thick, practically
devoid of any sandy or silty interbeds (Fig. 5.38).
The clayey intervals like those occurring on Bădislava River have been considered
as offshore-type facies (Jipa et al., 1999). This interpretation is based on the
lack of sand or silt intercalations, which suggests a calm sedimentation environment,
outside the sand material influxes.
Presently, we believe that the calm environment aspect is better explained as
a result of the lack of sand particles supply, because the clay deposits occur in the
proximal, sub-Carpathian margin of the basin. Consequently, the littoral clay deposits
could serve as markers of the sediment-starved time intervals.
5.6. CONCLUSIONS
The Dacian Basin sediment accumulation displaying features generated by wave
and storm action have been attributed to the shoreline environment.
A separation was made between lower energy and higher energy wave-dominated
shoreline environment, according to the thickness of the sandy units intercalated
in the clayey sequence and to the presence of the coarsening upward
trend. The sequences attributed to the lower or higher energy shoreface might also
represent sediment accumulation in the lower or middle shoreface area. The rate
of sediment influx could also control the character of the two types of shoreline
sequences.
Parallel laminated shoreface sediments accumulated in a very high energy
shoreline environment. The trough cross lamination and/or wave ripples at the upper
part of sequence indicate that the environment was getting more tranquil at
the end of the high energy event.
Shell beds in the Dacian Basin shoreline environment are of detrital origin, resulting
by current transport and sedimentation. The shell accumulation required
a high energy transport agent, acting in the shoreline or near shore environment.
The storm-generated currents represent the agent able to transport, concentrate
and accumulate the shells.