Subsurface geology of the Ariana region (Diapir Zone, northern Tunisia) by means of gravity analysis

Gravity data were used to investigate subsurface geology in the Ariana region from the Diapir Zone in Tunisia. Our study area is located in the north-eastern part of the Maghrebides affected by the Alpine orogeny. Despite the smooth topography and the low density of the Quaternary series, integrated geological data and gravity responses (Bouguer anomaly and derivative mapping) help decipher the geological heterogeneities beneath the Quaternary overburden. The interpretation of the gravity data points to alignments of positive anomalies delineating two major orthogonal features that are thought to characterize the subsurface deep structures: 1) a lineament striking north-west at the emplacement of an actual horst bordered by a buried fault-system directed N140 and 2) a second counterpart striking north-east, and is clearly expressed in the surface outcrops. These principal structural features were described as the result of a regional tectonic, compressive phase dating the Miocene. This phase was marked by reactivation and oblique-slip displacements of regional faults; some of which (N070) are reverse and south-east vergent. Further faulting enhanced the ascension of Triassic evaporites in diapir structures. This tectonic evolution may be integrated in the regional tectonic scheme of Alpine orogeny induced by a collision between African and European plates.