Neogene Structural Evolution of the Southern Zone Chain ()

H. L. Kheidri; R S Zazoun Sonatrach

The area under study is located in the external zones of the Maghrebides fold belt. This (2) Phase D2 (-18 M.y.) : it is synchronous with represents the southern section of the Alpine the Miocene-2 deposits and responsible for origin. It is bounded from the North by the development of a “puli-apart” type basin and Bibans chain, which constitutes the “para the sliding of the South-Tellian nappes. autochthonous” formations, that consists of Actually, a single wide basin is taking place Mesozoic limestones-maris series. From the and extended from the Bibans chain in the South by the Meso-Cenozoic “foreland” shaley north to the present limit of the M’Sila basin limestones. The whole area is unconformably in the south. A generalised transgression overlaid by a sandy-shales miocene facies. occurs and spreads up on to the mountains. This phase of deformation is In the study area, the Neogene is individualised genetically associated to a dextral wrenching by two “foreland basins” (M’Sila and sub and is compatible with NE-SW striking Bibanique basins), which are separated by the minimum principal stress axis (03). polyphased Hodna chain. Therefore, It is at an external position regarding to the Bibans chain. (3) Phase D3 (-10 M.y.) It is a transppresive During the Neogene time, the southern zone of phase and contemporary to the Miocene-3 the Bibans chain was affected by several and deposits. This phase is responsible for the various tectomc regime activity that undoubtedly, development of the Hodna mountain and the controls the deposiüonal process. This is neighbouring heights and the Sous-Tellian dominated obviously, by alluvial deposits. nappes structuration, as well as, the Neogene basin shrinkage. Consequently, the basin is The integration of outcrops, seismic, and well located in M’Sila region. data in addfition to Idnematic strain, showed evidence of 3 phases of deformation This phase of deformation is likely to be atiributed to the “Riedel” model, which suggests (1) Phase Dl (-25 M.y.) It is contemporary of a senestral strike-slip fault regime, compatible the Miocene-1 deposits and responsible for a with NE-SW strilcing maximum compressive southward compressive-thrusting tectonic stress axis (01). regime that imtiated two “foreland basins”. The sub-Bibanque basin is located in the Basement structuration and pre-existing south of the Bibans chain and the M’Sila Hercynian faulting have, obviously controlled basin situated on the southern flank of synsedimentary-tectonic evolutlon of Neogene . This phase conforms to deposits. There is the good reason to believe that the maximum compressive stress axis (01) the paleogeographic limits can be attributed to a striking N-S, which previously described tilted blocks model. throughout the Atlasic system.

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