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Structural Modeling of North-Western Tunisia Inferred From Gravity Data

Abstract

Geological evolution of the western Mediterranean region presents complicated architectures, tightly associated with the orogenic processes that are closely bounded to the African and Eurasian plate convergence. Northern Tunisia is an orogenic segment of the Northern African Alpine belt (Maghrebides) which structural organization was affected by the shortening regime during the Miocene time. The investigation using transformed potential fields based on three efficient techniques (Enhanced Horizontal Gradient, Tilt Derivative and Euler deconvolution) correlated to surface geological information allowed a synthetic tectonic modeling of Northern Tunisia. Interpretation of the distributed gravity anomalies and subsurface density contrasts on Medjerda valley and surrounding areas, reveal complex structural outlines expressed by the coexistence of compressive outcropping and even sealed structures (J. Hairech, El Merdja) associated to extensive structures (i.e. Tessa, Beld Zitoun and Mellegue grabens). These structures resulted from the compressive tectonic regime dated Miocene in age. This structural architecture is interpreted as the consequence of the reactivation of inherited major fault systems in the form of conjugated strike-slip faults. Then, the E-W directed fault of Ghardimaou -Thibar, well defined by gravity lineaments, was reactivated as dextral strike slip faults. However, the N-S and NE-SW oriented faults were reactivated with a sinistral strike. These accidents shaped Northern Tunisian domains and contributed to its complex geological architecture. The evidenced pattern is therefore integrated in the compressive deformation regime marked by conjugated fault systems in response to the African and Eurasian plate convergence.