Paleomagnetic and magnetostructural study of Jurassic formations of Gara Djebilet (Tindouf Basin, Southwestern Algeria)
Résumé
Recent geochemical analyzes and 40Ar/39Ar datings of dolerite sills and dykes and basaltic
lava flows from Southwestern Algeria (Tindouf, Reggane, Bechar and Hank basins) have
shown that these rocks are related to the Central Atlantic Magmatic Province (CAMP). The
CAMP is one of the largest among the Mesozoic basaltic provinces identified and formed about
200 Ma ago as a preamble to the breakup of Pangea. These data were solid arguments for undertaking
geological observations and sampling for paleomagnetic studies and magnetic fabrics on
the CAMP formations. A network of three long doleritic dykes (198.9 ± 1.8 Ma) located in the
Tindouf Basin were targeted to clarify the structural context of their emplacement (magnetic
fabrics) and to determine a new reliable Mesozoic pole.
The magnetic fabric, in almost all the sections sampled, is defined mainly through grouping
of k1 and k2 axes on the dyke plane whereas axis k3 is almost perpendicular to the dyke
plane. This fabric can therefore be interpreted as the magma flow direction. The new Jurassic
paleomagnetic pole, of excellent quality, is very close to those obtained on detrital formations
of the Algerian Sahara and close to those recently determined on igneous formations of Morocco.
This new pole is also very close to the North African pole at 200 Ma. These results represent
a new contribution for a better knowledge of the geodynamic context during this period.