Seismic Imaging of Collapsed-Anticline Diapirs in Central Tunisia
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eismic Imaging of Collapsed-Anticline Diapirs in Central Tunisia M. Harzalia, *, H. Troudib, and J. Oualia aLaboratoire
Eau, Energie et Environnement, Ecole Nationale des Ingénieurs de Sfax, BP 1173, Sfax, 3038 Tunisia OMV (Tunesien) Production GmbH, Immeuble Waterside, Impasse du Lac Turkana Les Berges du Lac, Tunis, 1053 Tunisia *e-mail: [email protected]
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Received June 11, 2019; revised October 25, 2019; accepted February 4, 2020
Abstract—Central Tunisia is characterized by major fault systems, being ornamented by salt diapirs of the Late Triassic evaporite-rich interval. Salt movement began in the Late Triassic and continues to the presentday. Lasting halokinesis create pillows, diapirs, salt wall and salt-cored folds, sometimes, with collapse graben above. Salt diapir structures have been mapped and many regions collapsed diapirs are, perhaps, associated to salt removal. These structures were eroded resulting exposure and sub-aerial erosion by the Late Cretaceous to Paleogene uplift and post-Middle Miocene. The initial studies and findings related to salt structures in Tunisia suggesting a clear correlation between diapiric uplift and local tectonic structures. In particular, the N‒S and NW‒SE shortening trends during the Neogene and Quaternary folding strongly controlled the development of rows of diapirs and salt walls. The salt activities are controlled by tectonics as well as differential loading in the Triassic sediments over long distances, displaying that the mobilization of Triassic sediments covered the whole region and not just the zones near the single diapiric structures. Here we will focus also in the salt related plays and the associated petroleum systems with particular emphasis on trap types, reservoir and hydrocarbon migration pathways. Obviously, all these elements are linked together to certain degree and controlled by the salt tectonics. Keywords: inherited faults, salt structures, crestal collapse graben, Central Tunisia DOI: 10.1134/S0016852120040032
INTRODUCTION The Triassic evaporites triggered the generation of various types of salt-related structures, such as saltcore anticlines, diapirs, walls, pillows and crestal collapse grabens during a long interval of salt tectonic movement. According to [37], many if not most halokinesis structures started during periods of extension. This interpretation reveals that the great deformations accompanying salt diapirism and halokinesis are the principal trigger for salt tectonics. Salt tectonics is controlled, according to [19, 26], by extensional fault systems of the sub-salt basement and/or by the thin-skinned extension of the post-salt sedimentary cover [38], while they can develop further through tectonic inversion. Its effect in all processes of the hydrocarbon accumulation and the geometry at depth has carried a lot of consideration and significant interest in understanding the dynamics of the salt movement and the driving forces of deformation. Central Tunisia is developed as a passive margin during the Mesozoic, with Triassic
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