%0 Conference Proceedings %F Poster %T Late Miocene uplift and doming of Madagascar: topographic implications %+ Géosciences Rennes (GR) %+ TOTAL PAU %+ Université Toulouse III - Paul Sabatier (UT3) %A Delaunay, Antoine %A Robin, Cécile %A Guillocheau, François %A Dall’asta, Massimo %A Calvès, Gérôme %< avec comité de lecture %B European Geosciences Union General Assembly 2016 %C Vienne, Austria %V 18 %P EGU2016-12750 %8 2016-04-12 %D 2016 %Z Sciences of the Universe [physics]/Earth Sciences/StratigraphyConference poster %X Madagascar is an Archean to Neoproterozoic continental crust surrounded by transform, oblique and divergentmargins: the oblique Morondava Basin to the west, pounded by the Davie Fracture Zone, and to the north, thedivergent Mahajanga (Majunga) Basin connected to the Somali Oceanic Basin. This 1600 km long island is ahigh axial plateau with elevations from 1200 to 1800m. The top of the plateau corresponds to weathered planationsurfaces (etchplains), bounded by more or less high scarps.We here present geological arguments for the age and the timing of the Madagascar Plateau. This analysis is basedon a double, coupled analysis of the onshore geomorphology (stepped planation surfaces) and the offshore marginstratigraphy (seismic stratigraphy and wells).The geomorphological analysis is based on a characterization, a mapping and dating of stepped planation surfaces(mantled to stripped etchplains, pediments to pediplains). The dating is based on their geometrical relationshipswith dated magmatic rocks. The difference of elevation between two planation surfaces (corresponding to localbase level) provides a proxy of the uplift. The sequence stratigraphic analysis is based on a biostratigraphicreevaluation of 4 industrial wells (foraminifers and nannofossils on cuttings). Uplift periods are characterized by(1) seaward tiltings of the margins overlain by planar reflectors, (2) forced regression wedges and (3) upstreamerosions of older sediments recorded by fauna/flora reworking.(1) During Paleocene to Middle Miocene times (66 to 13 Ma), Madagascar is a quite flat low elevation domainwith remnants of an oldest pre-Madagascar Trap (90 Ma) surface. This low relief is highly weathered with growthof numerous lateritic profiles and surrounded by large carbonate platforms with no siliciclastic sands influx.(2) The Late Miocene is the paroxysm of uplift with (1) a tilting of the margin (Morondova), (2) an increase of thesiliciclastic sand flux since middle Miocene and (3) a major stepping of dated planation surfaces.(3) The end result of this uplift is a convex up shape pattern for the end Cretaceous surface weathered duringEocene times, creating the present-day dome morphology (with a central plateau) of Madagascar.(4) The amplitude of this uplift can be estimated based on the present-day elevation of Late Eocene lagoonalsediments located 100 km north-east of Toliara and now at an elevation of 900m. If the absolute sea level wasaround 50 m (Miller et al., 2005) above present-day sea level during Late Eocene times, this means a surface upliftof around 850 m.(5) The mechanism of this uplift has to explain a very long wavelength deformation (x1000 km) necessary due tomantle dynamics. The relationships with the other East African domes (Ethiopia, East Africa, South Africa) arediscussed.This study was founded by TOTAL and IFREMER in the frame of the research project PAMELA (Passive MarginExploration Laboratories %G English %L insu-01308836 %U https://insu.hal.science/insu-01308836 %~ INSU %~ UNIV-TLSE3 %~ UNIV-RENNES1 %~ UR2-HB %~ CNRS %~ GR %~ OSUR %~ GIP-BE %~ UR1-HAL %~ UR1-SDLM %~ UR1-SDLMJONCH %~ GR-PPDB %~ UNIV-RENNES2 %~ TEST-UNIV-RENNES %~ TEST-UR-CSS %~ UNIV-RENNES %~ INRAE %~ UR1-ENV %~ GR-R %~ UNIV-UT3 %~ UT3-INP %~ UT3-TOULOUSEINP %~ TEST3-HALCNRS