"Cadre Sédimentologique et Paléoenvironnemental des Formations mio-pliocènes de la région de Guerrara"

Abstract

"The purpose of the sedimentological, sequential study and paleoenvironnemental realized on badly consolidated sandstones of Mio-pliocene of the area of Guerrara, are to reconstitute the positioning of these formations in the geological and environmental context total of Algeria. The geological recognition of the site and the series of analyses of laboratory realized reveal that this detrital formation of the continental terminal or latest (Neogene) probably occurred after a strong deterioration of the tertiary and mesozoïc formations. This series is made up of two principal sequences; MSII of higher Miocene and MSIII of Pliocene, which are separated by regional discontinuities d0, d3, d4. The means of transport dominating and the conditions of deposit reveal an endoreic area (basin), as testifies the presence of certain argillaceous minerals (palygorskite). The predominance of the blunted quartz grains in upper miocene presenting of the siliceous globules reveals a hydrous dominating mode. This formation settled in a frankly continental field under a mode of fluviatile and wind mixed transport. The mio-pliocene formation is notched, in North and the South, by many Wadis, which occurred after the lowering of the static levels of alluvial groundwater at the end of the Tertiary period. These static variations are revealed by the sedimentopedogenic cycles (sedimentary sequences). The surface quality of the grains the processions mineral and the sedimentary sequences reveal an alternation of perios to steppe climate, and periods with hot and wet climate at the top of each sets of this formation. The round quartz grains with traces of multiple shocks, packed by iron oxides, testify the end to a hydrous cycle and installation to the desert conditions."