Mechanical relationship between strike-slip faulting and salt tectonics in the Northern Tunisian Atlas: The Bir-El-Afou salt structure. (January 2022)

• Record Type: Journal Article
• Authors: Amri, Zayneb; Masrouhi, Amara; Naji, Chahreddine; Bellier, Olivier; Koyi, Hemin
• Is Part Of: Journal of structural geology. Volume 154(2022)
• Publication Date: 2022-01
• Subjects: Salt diapir -- Pull-apart -- Restraining bend -- Inversion -- Tunisia; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2021.104501
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: Wide variety of salt structures –from typical diapirs to large allochthonous salt sheets– are recognized in the Northern Tunisian Atlas. In this study, we present for the first time the presence of a diapiric structure, Bir-El-Afou Salt Structure (BEASS), which has formed in response to strike-slip tectonics. Structural mapping, mesoscale field observations, fault kinematic analysis, and interpretation of gravity data are used to interpret BEASS, which is currently associated with a restraining bend. The present-day NNE– trending restraining stepover is formed as a result of E-W dextral fault system. We assume that the restraining stepover is a product of the inversion of a pre-existing pull-apart basin that formed during the Cretaceous South Tethyan extension. Tectono-sedimentary relationship is used to argue for an early Cretaceous NW-SE regional extension and local transtension. During the opening of the pull-apart basin, salt movement took place in the southwestern corner of the basin which must have thinned due to its extension facilitating diapiric emplacement. Diapir growth during Aptian was followed by brief salt flow from the diapir crest towards the basin forming a salt sheet. A period of Tertiary contraction resulted in the inversion of the pull-apart basin and consequently, squeezing of BEASS. Highlights: Salt diapir, associated with releasing stepover in response to strike-slip tectonics, is examined. During the opening of the pull-apart, salt diapir took place in the corner of the basin. 5-km–long salt sheet is formed as a result of salt extrusion from the diapir toward the basin. The present-day squeezed diapir in a restraining stepover, is the result of the pull-part basin inversion.