Determining of a complex structure consisting of detachment, fault-bend and fault propagation folds in the collapse structure of Zaghouan-Bouficha (Bouficha region, north eastern Tunisia)

Abstract

The structural study in Bouficha region based on subsurface investigation has allowed determining the geometry of deformations. These deformations are represented by faults of NE–SW and NW–SE directions and folds of NE-SW mean orientation. The aim of the present paper is to demonstrate the structural style of these folds and reconstruct their evolution. Data obtained from a seismic profile that cross longitudinally the collapse structure of Zaghouan-Bouficha, have revealed the structure of fault-related folds. The interpretation of the NW-SE seismic profile revealed two fault-propagation folds, a detachment fold and two fault-bend folds in the Zaghouan-Bouficha collapse structure. From the South-east to the North-west, the seismic profile shows: (1) a fault-propagation fold built on a horizontal detachment level situated in the Triassic series linked to a ramp, (2) a detachment fold formed on a detachment level in the Triassic series, (3) a second fault-propagation fold formed on a horizontal detachment in the Triassic series and a ramp, (4) a fault-bend fold overcomes the second fault-propagation fold. It formed over two detachment levels which are connected to a ramp of a dip towards the SE indicating a displacement to the North-west, (5) a second fault-bend fold formed over two detachment levels which are connected to a ramp of a dip towards the NW indicating a displacement to the South-east. The evolution reconstruction of these fault-related folds shows that they formed during the Late Miocene and Plio-Quaternary compressive phases. This study shows also an analogical modeling that explains some evolutionary steps of the determined deformations.