This work is based on apatite fission-track analysis of samples (mostly
granites) from the basement of the Cretaceous-Tertiary Phosphate and
Ganntour Plateaus, exposed in the Jebilet and Rehamna massifs (Western
Meseta, Morocco). This basement belongs to the Carboniferous-Early
Permian Variscan Belt, and the earlier marine onlap is Late Triassic in
age. However, the AFT ages are post-Triassic and different in the
Jebilet (186203 Ma) and Rehamna (148-153 Ma). Track length modelling
support the occurrence of moderate heating events during the Jurassic
and the Eocene, respectively, with cooling during the Permian and
Cretaceous intervals. These results are partly accounted for by
considering a moderate subsidence during the Late Triassic-Liassic,
which is a noticeable change in the regional paleogeographic concept of
``West Moroccan Arch''. However, the discrepancies between the AFT
results from the studied massifs make necessary to explore further
explanation. We interpret the observed discrepancies by the difference
in age and depth of crystallization of the sampled granites in the
Variscan Orogen, i.e. 330 Ma, 5-6 km in the Jebilet versus similar to
300 Ma, 8-10 km in the Rehamna. The importance of the Late
Jurassic-Early Cretaceous uplift and erosion of the entire Meseta and
that of its Late Eocene burial are emphasized. (C) 2009 Elsevier B.V.
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