Abstract:
Intraplate deformation in the Murzuq Basin of SW Libya and the Illizi and Ghadames basins of eastern Algeria is investigated through the interpretation of regional seismic lines, gravity and magnetic surveys, satellite imagery and kinematic analyses of outcrop data. Five
structural lineament trends have been identified: NNW-, NE- and N-striking Precambrian
basement structures which are overprinted by ENE- and WNW-striking Late Carboniferous
- Mesozoic fracture systems. These structural lineaments define distinct structural domains,
with central Algeria characterised by NE-striking faults whilst NNW-striking faults are
restricted to SW Libya and SE Algeria. This structural heterogeneity allowed basins to evolve independently of one another. NNW and
N-striking faults were active during the Early Palaeozoic rifting of Gondwana and the
opening and subsequent closure of the Proto-Tethyan Ocean. The kinematics of these early
structural events are uncertain in the absence of a clear understanding of Early Palaeozoic
plate margin movements. Analysis of Late Palaeozoic plate kinematics shows that Late
Carboniferous NW-SE compression and uplift was followed by Triassic-Jurassic NW-SE
extension of orthogonal fault systems in Algeria. Early Cretaceous N-S extension was
replaced by Late Cretaceous- CenozoicN W-SE compression which promoted uplift and
erosion of the basins.
Apatite fission track analyses of Ordovician and Devonian samples, together with sonic
velocity analysis of the Silurian Tanezzuft Formation, indicate maximum burial in the
Jurassic-Early Cretaceous followed by c. I km of Late Cretaceous to Tertiary uplift and
erosion. The Mesozoic - Cenozoic evolution of North Africa relates to three successive
rifting events associated with the development of the Equatorial, South and North Atlantic
and the opening and subsequent closure of the Tethyan Ocean. Movements of the North
African Megashear system have transferred plate margin deformation into the cratonic
interior largely by strike-slip reactivation of pre-existing fault systems.
