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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Re-understanding of the Tectonic Feature of Chelif Basin in North of Algeria
(1) Research Institute of Petroleum Exploration & Development- Northwest,Petrochina, Lanzhou, China.
Chelif basin, situated in the north of Algeria,is marked by extremely complex tectonic structure. Due to the application of model of tension-rift lake basin by the former researchers, there are several tectonic phenomenon that can’t be explained. After comprehensive analysis with regard to the tectonic movement, the field investigation and the seismic data, new understandings as the follows have been obtained by this paper.
The Chelif basin is a Meso-Cenozoic superimposed basin that has undergone multi-period rebuilding of compression, contemporaneous extension as well as partial gliding movement. It has mainly experienced four periods of thrust-nappe movement which turned newer gradually from south to north, namely the early Eocene, the late Early Miocene, the late Late Miocene and the Pleistocene. As a result, three regional angular unconformities between the Miocene / Oligocene and the Cretaceous, the upper Miocene and the lower Miocene, the upper Miocene and the Pliocene have been formed.
The overall tectonic features are characterized by the superimposition of multi-periods nappe structures, and the synchronous extension structures paralleling the structure strikes, the partial strike-slip structures under the regional compression background. The multiple period of tectonic movements gave rise to the strong deformation and extraordinary tectonic complexity of this basin. A wide range of tectonic models have been formed consequently. Anticlines ,tectonic inverses ,wedge-shaped thrust blocks, gravity collapses, back-back thrust structures are well developed.
Taking the stress mechanism, the delivery mode, the section shape and the plane combination into account, the faults of Chelif basin consists of five types: the imbricate arrangement thrust faults along the tectonic strike,the huge synchronous normal faults in accordance with the tectonic strike in front of the mountains ,some small synchronous normal faults being perpendicular to the tectonic strike because of the development of nosing structures, the right-lateral displacement fault that is 45 degree to the tectonic strike and the right-lateral strike-slip faults in the plane of which performs broom-like arrangement.