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Phanerozoic evolution of the Guiana Shield in northern South America is poorly known and remains an important question for source-to-sink studies. As part of the Source to Sink project TOTAL R&D-BRGM-INSU, this study presents a suite of 40 new apatite fission track analysis results from French Guiana, Surinam and north Brazil. Inverse thermal history modelling reveals a marked, albeit poorly constrained, period of relatively high temperatures (temperatures > 110 °C) during the Jurassic (200-150 Ma), i.e. prior to the generally accepted timing of the Equatorial Atlantic Ocean opening (150-110 Ma). Lower temperatures are recorded on the southerm flank of the Amazonas Basin and a little portion of the Surinam interior. All data reveal then a protracted phase of cooling starting from ~150 Ma and representing the main event during the Mesozoic and Cenozoic for French Guiana and Surinam basement. A second thermal event is nevertheless recorded after the deposition of Upper Jurassic and Lower Cretaceous detrital sedimentary rocks on the northern flank of the Amazonas Basin. Maximum temperatures for this event (80-100 °C) are reached during the middle Cretaceous (115-90 Ma). Implications of these new results for the Guiana Shied evolution and the Equatorial Atlantic opening are discussed.

International audience; The objective of this work is to establish the sediment routing systems of the West African and Guyana Shieldsto the rift and passive margin basins of the Equatorial Atlantic at geological time scales (since 200 Ma). Thesemargins, alternating transform and divergent segments, show a strong structural variability in the margin width,continental geology and relief, drainage networks and subsidence/accumulation patterns. We analyze thesesystems combining onshore geology and geomorphology as well as offshore sub-surface data. We quantifyaccumulation histories in the passive margin basins histories taking into account the whole depositional system(from the shoreline to the most distal deposits onto the oceanic crust). We correct these from remaining porosityand in-situ production (mainly carbonates) and compute uncertainties related to depth conversion, absolute ageattribution from biostratigraphy as well as porosity and in-situ production corrections. We verify that the observedtrends in accumulation rates are robust despite the saddler effect related to the increase in temporal resolution withtime. We compare accumulation histories to paleo-geographic maps of sources and sinks established at continentscale. These maps, spanning the continental domain of West African and Guyana Shields and their offshore basinssince 200 Ma, give the framework of the evolution of the sediment routing system through time.Along the African margin, we defined the stratigraphic architectures of the 3 sub-basins (Sierra Leone/Liberia,Ivory Coast, and Ghana/Togo/Benin) to establish their post break-up accumulation (since ca.100 Ma). Accumulationsrates are significantly higher during (i) the Cenomanian that may be related to the erosion of EquatorialAtlantic rift-shoulders, (ii) the Maastrichtian that may be related to either the tectonic inversion of western Africaat the time or a change in the erosion capacity in the continental drainage area driven by climate change and (iii)the Oligocene that marks a major drainage reorganization in West Africa following the rise of the Hoggar and amajor sea-level fall in Rupelian (ca.30 Ma).Along the conjugate South American margin, we are currently defining the stratigraphic architectures of 2sub-basins (Guyana/Suriname to the West and Foz d’Amazonas to the East) that will allow for establishingtheir accumulation histories. The long term stratigraphic trends of those basins shows : (i) the Central Atlanticrifting in the Guyana/Suriname basin (165 – 156 Ma) and the Equatorial Atlantic rifting ([U+F07E]100 Ma)in the Foz d’Amazonas basin; (ii) massive syn-rift deposits in the western Guyana/Suriname; (iii) a progressivedecrease of the clastic input during most of the Paleogene allowing for carbonate platform deposits followedby (iv) a major clastic accumulation in the Foz d’Amazonas basin since the Upper Miocene resulting froma major drainage reorganization on the Guyana Shield during the Neogene (drainage inversion toward the Atlantic).

One of the major issues of the evolution of continental lithospheres is the detachment of the lithospheric mantle that may occur under certain conditions and its impact on the surface. In order to investigate the dynamics of continental delamination, we performed a parametric study using physically scaled laboratory models. The adopted setup is composed of a three-layers visco-elastic body (analog for upper crust, lower crust, lithospheric mantle) locally thickened/thinned to simulate a density anomaly (lithospheric root) and an adjacent weak zone, lying on a low viscosity material simulating the asthenosphere. The results emphasize the interplay between mantle flow, deformation, surface topography and plate motion during a three-phases process: (1) a slow initiation phase controlled by coupling and bending associated with contraction and dynamic subsidence, (2) lateral propagation of the delamination alongside with extension and a complex topographic signal controlled by coupling and buoyancy, while poloidal mantle flow develops around the tip of the delaminating lithospheric mantle, and (3) a late phase characterized by a counterflow that triggers retroward motion of the whole model. A semiquantitative study allows us to determine empirically two parameters: (1) an initiation parameter that constrains the propensity of the delamination to occur and correlates with the duration of the first stage, (2) a buoyancy parameter characterizing the delamination velocity during late stages and therefore its propensity to cease. Finally, we point out similarities and differences with the Sierra Nevada (California, USA) in terms of topography, deformation and timing of delamination.

International audience; present work investigates the formation of curved ranges and syntaxes with scaled laboratory experiments. We simulated subduction and collision processes comparable to India-Asia configuration involving a continental upper plate and a subducting plate composed of an oceanic lithosphere and a continental indenter. The experiments reveal that the shape of the mountain range (concave, straight, or convex) and the development of syntaxes are controlled by the subduction interface, the buoyancy number (Fb) of the upper plate (i.e., thickness and viscosity), and the boundary conditions. Four end-members regimes of indentation can be defined depending on the range shape and dynamics of the upper plate. The curvature of the range is convex toward the subducting plate with syntaxes for a weak subduction fault and concave without syntaxes for a strong subduction fault. Convex curvature and syntaxes form by overthrusting of upper plate material on the subducting plate, which is faster at the center than at the extremities. They are associated with a rather flat slab (underthrusting) during continental collision. Low-Fb experiments show less pronounced curvatures associated to thickening comparable to the early stages of the India-Asia collision. In contrast, a thick and weak upper plate (high Fb) leads to gravity collapse that increases the amplitude of the curvature and lateral escape, similar to the late evolution of the Himalaya-Tibet system. Important lateral decoupling on the sides of the indenter enhances the indentation and produces sharper syntaxes.