ARHIVELE OLTENIEI - Universitatea din Craiova

368Sandu BoengiuWe can appreciate that the main features of the accumulation fields presentin the interval Dacian-Romanian from western Oltenia are: the regularity of thedeposits, the persistency of the plain and the gradual withdrawal of its surface.Generally, the sedimentation, especially during the Dacian, was calm andcharacterized by a slow subsidence. All the conditions were favourable to thedevelopment of certain marshes that covered a large part of the territory locatedwest of the Olt and displayed deltas, wind dunes, and fluvial contributions.By analysing the thickness of the lithofacies deposits and the distributionof sands, one can state that the Pliocene lake was limited by numerous convergentrivers that generally corresponded to some present rivers: the Olt, the Jiu, theMotru 4 . These rivers deposited materials at their mouth in lacustrine deltas withsubmerged and low declivity surfaces that favoured the formation of amplemeanders within the submerged areas and levees along the channels.Even during the accumulation of Berbeşti formation, within the distalsubmerged areas, there appeared submerged offshore bars among which theredeveloped flood plains rapidly clogged and usually transformed into marshes,which had a short existence during the fluvial phases and a long one during thetelematic phases, when peat usually accumulated.According to the coal accumulations it can be deduced that themorphology of the basin evolved as an alluvial lacustrine plain with momentswhen the coal-generating marshes induced the Foredeep and the MoesicPlatform at the same time. Such a situation occurred (as we have alreadyillustrated) during the accumulation of the V coal bed, which covered the largestsurface from western Oltenia.c) The climatic factorThe climatic factor directly and decisively influences the developmentand the regional distribution of vegetation. The paleontological features 5emphasized that the cooling of the climate continued in Oltenia during the UpperPontian. The flora elements characteristic to the temperate climate becameexclusive making up a vegetal cover characteristic to an average altitude ofabout 1,000 m, on the land neighbouring the sedimentation basin 6 .The climatic factor is the same on large surfaces and it is characterizedby rainy periods, when the water level increased in the peat bog and by drierperiods, when the water level decreased. In this last case, the formation of peatwas interrupted and it was separated by thin intercalations in many lakes.4 N.Ţicleanu, Modèle génétique conceptuel des accumulations de charbon du BassinDacique, Cronostratigraphie und neostratotipen, Editions de l’ Académie Roumaine, Bucarest,1995, p. 8-10.5 S. Boengiu, C. Enache, Des faciès paléontologiques mio-pliocenes en Oltenia, in Etudeset communications, Sciences de la Terre, Vol. XVI, Craiova, Editions MJM, 2000, p. 43-47.6 L. Apostol, C.Enache, Etude de l’espece Dicerorhinus megarinus (de Christol) dubassin carbonifère du Motru, in “Trav. Mus. Hist. Nat. Gr. Antipa.”, vol. XX. Bucureşti, 1979,p. 533-542.