Surface uplift and topographic rejuvenation of a tectonically inactive
range: Insights from Anti-Atlas and Siroua Massif (Morocco)
Abstract
The Atlas-Meseta intracontinental orographic system of Morocco
experienced recent, large-scale surface uplift as documented by elevated
late Miocene, shallow-water marine deposits exposed in the Middle Atlas
Mountains. The Anti-Atlas Mountains do not present any stratigraphic
records that document regional vertical movements, however, the presence
of a high-standing, erosional surface, and the transient state of river
networks, provides insights into the uplift history of the belt and the
mechanisms that drove it. Here, we combine geomorphic and stream
profiles analyses, celerity of knickpoints and linear inverse landscape
modelling with available geological evidence, to decipher the spatial
and temporal variations of surface uplift in the Anti-Atlas and the
Siroua Massif. Our results highlight the presence of a transient
landscape, and document a long wave-length topographic swell
(~ 100 x 600 km) with a maximum surface uplift of
~1500 m in the Siroua Massif and ~1100 m
in the central Anti-Atlas starting from ~10 Ma, in
association with late Miocene magmatism in the Siroua and Saghro Massif
and contractional deformation in the High Atlas. Uplift rates for the
central Anti-Atlas range between 70 and 180 m/Myr, fall within the same
order of the rates obtained from uplifted marine deposits suggesting a
similar deep-seated mechanism of uplift most likely related to
astenopsheric upwelling. Overall, our approach allows to quantitatively
constrain the transient state of the landscape and the contribution of
regional surface uplift on mountain building processes.