Abstract
The Tunisian Atlas is a foldbelt of unusual complexity developed in a stratigraphic succession of Mesozoic and Tertiary age. The folds range in style from simple, narrow-crested box folds separated by broad relatively flat synclines to complex growth folds flanked by numerous unconformities. Many of the anticlines are cored by highly deformed Triassic-Liassic evaporites. Locally the structures are cut by high-angle reverse faults and late-orogenic normal faults. Fold trends are both variable and intersecting and the folds tend to die out abruptly along strike. A model is proposed in which three successive and contrasting tectonic regimes have operated since the early Mesozoic to produce the structural complexity of the Tunisian Atlas: (1) block faulting associated with rifting of the North African continental margin, which in Tunisia began by, at least, the early Jurassic; (2) diapiric emplacement of the Triassic-Liassic evaporites into the overlying strata beginning in the early Cretaceous; and (3) folding of the cover strata in response to regional compression in the early Miocene through Pleistocene. Structures formed during the Neogene compressional phase were controlled by mechanical anisotropies in the cover, principally thickness and facies variations, caused by the early block faulting and diapirism. Although detachment and decollem nt glide of the cover strata on the Triassic-Liassic evaporites appear to have operated locally, regional shortening of the pre-Mesozoic basement is considered to be the principal driving mechanism for folding in the Tunisian Atlas. End_of_Article - Last_Page 521------------
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