Tectonic, magmatic and sedimentary evolution of the strike-slip margins of eastern Austral Africa (Mozambique Channel): palaeogeographic constrains

Abstract

<p>The geological evolution of the Mozambique Channel sensu largowas controlled by three major transfer zones (Davie, Mozambique and Agulhas/Falklands), (1) related to the migration of four continents (Africa, Madagascar, Antarctica, South America), (2) recording five major volcanic episodes from 186 Ma to today and (3) contemporaneous of the uplift of several plateaus (e.g. Southern African Plateau), affecting a quite heterogeneous lithosphere of Archean to Neoproterozoic ages. This is therefore a unique area for a better understanding of (1) the evolution of transform margins in a volcanic setting and (2) the relationships between deformation, relief growth and sediment routing evolution. We established in the frame of the PAMELA (Passive Margin Experiment LAboratory) project (TOTAL, IFREMER, CNRS) a chart and nine paleogeographic maps (with tectonic structures, magmatism, catchments and sediment routing system) to better constrain the timing of evolution of this domain. The main results are as follows:</p><p>(1) 255-240 Ma: a first E-W extension (Karoo “Rifts”) with no ocean opening;</p><p>(2) 185-160 Ma: a second NW-SE extension between Antarctica/Madagascar and Africa coeval of the Karoo Large Igneous Province and initiation of volcanic margins along the future Somali Ocean;</p><p>(3) 160-145 Ma: major change of the plate migration toward a N-S extensional initiation of very oblique margins along the Mozambique Fracture Zone (FZ), indicating an Antarctica motion toward SSE;</p><p>(4) 134 Ma: onset of the migration of the Falkland continental domain along the Agulhas FZ;</p><p>(5) 115 Ma: major deformation of the four plates with (i) end of the southward migration of Madagascar and (ii) major inversion along the Davie FZ (initiated around 135 Ma) and uplift of Madagascar;</p><p>(6) 92-70 Ma: uplift of the Southern Africa Plateau first eastward (92 Ma) and second westward (81-70 Ma);</p><p>(7) 40 Ma: onset of the uplift of the Zimbabwe/Zambia/Malawi Plateaus, East African Dome and Madagascar Plateau – last uplift of the Southern African Plateau;</p><p>(6) 11-5 Ma: acceleration of the uplift of the Zimbabwe/Zambia/Malawi Plateaus and East African Dome – growth of a dome crossing the Mozambique Channel from Madagascar to southern offshore of the Limpopo Plain.</p>