Résumé:
"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."
