Evidence for an east–west regional gravity trend in northern Tunisia: Insight into the structural evolution of northern Tunisian Atlas
, Chokri Jallouli, Saad Mogren, Kevin Mickus, Mohamed Moncef Turki . 2013
The Atlas orogeny in northern Algeria and Tunisia led to the destruction of Tethys oceanic lithosphere and
cumulated in a collision of microplates rifted off the European marginwith the North African continental margin.
The location of the boundary between African plate and Kabylian microplate is expressed in northern Algeria by a
crustal wedge with double vergence of thrust sheets, whereas in northern Tunisia the geologic environment is
more complex and the location of the plate boundary is ambiguous. In this study, we analyzed gravity data to
constrain the crustal structure along the northernmargin of Tunisia. The analysis includes a separation of regional
and residual gravity anomalies and the application of gradient operators to locate density contrast boundaries.
The horizontal gradient magnitude and directional gradient highlight a prominent regional E–Wgravity gradient
in the northern Tunisian Atlas interpreted as a deep fault (active since at least the Early Mesozoic) having a
variable kinematic activity depending on the tectonic regime in the region. The main E–W gravity gradient
separates two blocks having different gravitational and seismic responses. The southern block has numerous
gravity lineaments trending in different directions implying several density variations within the crust, whereas
the northern block shows a long-wavelength negative gravity anomaly with a few lineaments. Taking into
account the geologic context of theWestern Mediterranean region, we consider the E–W prominent feature as
the boundary between African plate and Kabylian microplate in northern Tunisia that rifted off Europe. This
hypothesis fits most previous geological and geophysical studies and has an important impact on the petroleum
and mineral resource prospection as these two blocks were separated by an ocean and they did not belong to the
same margin.
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