THE PERMIAN-TRIASSIC TRANSITION AND THE BEGINNING OF THE MESOZOIC SEDIMENTATION OF HIGH ATLAS OF MARRAKECH AND ARGANA BASINS: ATTEMPT OF CORRELATION AT WESTERN PERITETHYAN DOMAIN
Résumé
The Permian-Triassic Boundary is an important interval, intensely studied to clarify climatic, biotic and
environmental conditions. Continental sedimentation of the studied interval, upper F2/F3/lower F4 and upper
T2/T3/lower T4 units, respectively in the High Atlas of Marrakech and Argana Valley spans from late Permian,
dated from vertebrates, to Middle Triassic. It records all changes in the depositional environments under
tectonic and climatic control. The sedimentological study aimed to characterize the Permian-Triassic transition
by a sedimentological outcrop analysis, to recognize sedimentary facies, facies associations, to reconstitute the
depositional history and the palaeogeography evolution from the end of the Permian to the beginning of the
Triassic siliciclastic succession. Finally, from depositional sequences we propose stratigraphic correlation at
the scale of Morocco basins and the western Peri-Tethyan domain. The late Permian (upper F2/upper T2 units)
facies association represents fluvial fans in a dry alluvial plain. The Early Triassic F3 /T3, dated from food
prints, and F4a/T4a units rest unconformably on the Permian strata, and consist of (i) arid alluvial fans, (ii)
aeolian deposits, (iii) palustrine-lacustrine deposits, (iv) floodplain, (v) meandering river and (vi) braided river.
The Anisian F4b/T4b units represent axial fluvial plain of high sinuosity rivers. The dynamics of alluvial fan,
fluvio-lacustrine, eolian deposits, the synsedimentary tectonic and the baselevel fluctuations will be taken into
consideration during the filling of the sedimentary basins to constrain the stratigraphic cycles. The evolution
of early Triassic environments constitutes a major stratigraphic cycle with retrogradational and progradational
trends, and is bounded by surfaces correlated at the scale of Morocco basins. The Anisian units are
characterized by floodplain and meandering river deposits, and represent the beginning of another stratigraphic
cycle. The stratigraphic cycle can be discussed at the scale of western Peri-Tethyan domain