The evolution of the Lansarine–Baouala salt canopy in the North African Cretaceous passive margin in Tunisia

Abstract

Detailed geological mapping, dating, and gravimetric and seismic data are used to interpret the Lansarine-Baouala salt structure (North Tunisia) as a salt canopy emplaced during the Cretaceous Period. The extensional tectonic regime related to the Cretaceous continental margin offered at least two factors that encouraged buried Triassic salt to extrude onto the sea floor and flow downslope: (i) extension induced normal faults that provided routes to the surface, and led to the formation of submarine slopes along which salt could flow; (ii) this structural setting led to differential sedimentation and consequently differential loading as a mechanism for salt movement. The present 40-km-long Lansarine-Baouala salt structure with its unique mass of allochthonous Triassic salt at surface was fed from at least four stems. The salt structure is recognized as one of the few examples worldwide of a subaerial salt canopy due to the coalescence of submarine sheets of Triassic salt extruded in Cretaceous times.

Major faults, salt structures and paleo-ridge at tectonic nodes in Northern Tunisia: contribution of tectonics and gravity analysis

“…Masrouhi et al (2013) exhibits the crucial role of Teboursouk NE-trending major fault in Lansarine structure with E-trending-associated faults. The study of Bir Afou structure by Ben Chelbi et al (2006) shows that this structure is placed into a tectonic intersection of two major faults trending respectively N45 and (major fault segment Tunis them) N120.…”

“…Where the Triassic series are interpreted as an effusion or a salt sheet, the authors speak about a tilted-block configuration (Ghanmi et al 2001;Vila et al 1996aVila et al , b, 2002 with a preferential collapse to the north and NW compared to the source material flow (Vila et al 1994a, b. Marzougui et al 2008Masrouhi et al 2013).…”

“…This paleo-structuring has been installed during the Jurassic and Cretaceous extensional phases same time as the opening of the Tethys and the genesis of the Tunisian trough (Soussi 2002;Souquet et al 1997. Masrouhi et al 2013.…”

“…1) and para-autochtonous structures known as "imbricated zone" in the southern part (study area). The current structural pattern of this area derives from the successive compressional tectonic phases generated by the AfricanEurasian plates convergence, Eocene phase with WNW-ESE to NW-SE shortening (Bouaziz et al 2002;Ben Ayed 1986;Masrouhi et al 2007Masrouhi et al , 2008Masrouhi et al , 2013Frizon de Lamotte et al 2009;Guiraud and Bosworth 1997;Masrouhi and Koyi 2012;Melki et al 2011;Tlig et al 2010;Talbi et al 2008), Tortonian phase with NW-SE shortening (Burollet 1956;Bouaziz et al 2002;Chihi 1992;Dlala 1992;Rouvier 1977;Zargouni and Ruhland 1981;Talbi et al 2008;) and Quaternary N-S shortening phase (Ben Ayed 1993;Dlala 1992;Bahrouni et al 2014). The structural ambiguity in Northern Tunisia is due to the halokinesis interference guided by major faults shaping the present structural scheme.…”

“…Concerning Triassic salt bodies, some authors interpreted them as rooted diapirs (Zargouni 1975(Zargouni , 1977Perthuisot 1978Perthuisot , 1981Ben Mehrez et al 2009;Masrouhi et al 2014); others interpreted them as thrust sheet (Truillet and Turki 1980;Truillet and Delteil 1982), whereas others expound the salt glacier model (Masrouhi and Koyi 2012;Masrouhi et al 2013;Vila et al 1994aVila et al , 1994bVila et al , 1996aVila et al , 1996bBen Chelbi et al 2006). In our case study, the Bazina salt Triassic structure is an example among many others which are interpreted differently.…”