We present the structure and evolution of the eastern part of the Demerara plateau, offshore French Guiana, from the analysis of geophysical data collected during GUYAPLAC cruise. This area is located at the intersection of a transform segment and a divergent segment of a continental margin related to the Early Cretaceous opening of the Equatorial Atlantic. The main structures are NNE-SSW to NNW-SSE trending normal faults on the eastern edge of the plateau, and WNW-ESE to NW-SE trending acoustic basement ridges on its northern edge. When replaced in their Albian position, these structures appear to be parallel to the coeval oceanic accretion axis and transform faults, respectively. The most striking structures are related to a post-rift but syn-transform tectonic inversion, producing E-W to WNW-ESE trending folds, sealed by a regional unconformity. This shortening can not be related to ridge push, but is probably related to a plate kinematic change 15 My ago, that modified the deformation in the vicinity of the transform fault. Late post-rift evolution also includes a significant Tertiary oceanward tilt of the edge of the Demerara plateau. The driving mechanism of this late tilt is unclear, but may be related to a lithospheric flexure resulting from the loading of the abyssal plain by the Orinoco and Amazon deep-sea fans.Structure of the Albian to present day sedimentary cover of the Demerara Plateau Evolution of the deformation, with post-rift but syn-transform tectonic inversion Late post-rift tilt Discussions on the timing of transform versus rift deformation, on the ridge push, on the signification of unconformities in transform settings, on the regional topographic effects of the Amazone fan.
Related Content
Mechanism and timing of tectonic inversion in Cyrenaica (Libya): Integration in the geodynamics of the East Mediterranean
In the eastern Mediterranean, the South-Tethys paleo-margin experienced poly-phased rifting episodes during Paleozoic and Mesozoic times. This domain has been subsequently inverted by discontinuous events occurring since the Late Cretaceous as a consequence of the Africa-Eurasia convergence. The ...


The Alpine Tethys rifted margins: Reconciling old and new ideas to understand the stratigraphic architecture of magma-poor rifted margins
This study focuses on the assessment of the stratigraphic architecture of the proximal and distal Jurassic Alpine Tethys rifted margins. The aim of the study was to reconcile the major observations performed in the Alps through time with what is observed in present-day magma-poor rifted margins. ...
Geodynamic significance of the TRM segment in the East African Rift (W-Tanzania): active tectonics and paleostress in the Ufipa plateau and Rukwa basin
The Tanganyika-Rukwa-Malawi (TRM) rift segment in western Tanzania is a key sector for understanding the opening dynamics of the East African rift system (EARS). In an oblique opening model, it is considered as a dextral transfer fault zone that accommodates the general opening of the EARS in a N...


Crustal and uppermost mantle structure in the central US encompassing the Midcontinent Rift
Rayleigh wave phase velocities across the western arm of the Midcontinent Rift (MCR) and surrounding regions are mapped by ambient noise (8-40 sec) and earthquake tomography (25 – 80 sec) applied to data from more than 120 Earthscope/USArray stations across the central US. Receiver function...
The Moho in extensional tectonic settings: Insights from thermo-mechanical models
The lithospheric memory is key for the interplay of lithospheric stresses and rheological structure of the extending lithosphere and for its later tectonic reactivation. Other important factors are the temporal and spatial migration of extension and the interplay of rifting and surface processes....

3D Gravity Inversion of Northern Sinai Peninsula: A Case Study
The Sinai Peninsula has attracted the attention of many geological and geophysical studies as it is influenced and bounded by major tectonic events. Those are (1) the Mesozoic to Early Cenozoic tectonically active opening of the Tethys, the Late Cretaceous to Early Tertiary (Laramide) Syrian arc ...
Tectonic uplift mechanism of the goodenough and Fergusson Island gneiss domes, eastern Papua New Guinea: Constraints from seismic reflection and well data
The D'Entrecasteaux Island (DEI) gneiss domes are fault-bounded domes with ~2.5 km of relief exposing ultrahigh-pressure (UHP) and high-pressure (HP) metamorphic gneisses and migmatites exhumed in an Oligocene-Miocene arc-continent collision and subduction zone subject to Late Miocene to Recent c...

3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)
The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian–Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when com...
Post-breakup evolution of the Namibian margin: Constraints from numerical modeling
The Namibian margin evolution started 130 Myr ago after the breakup between South America and southern Africa. Today, it shows specific features: (i) an elevation and a bathymetry about 1000m higher than the surrounding areas, (ii) a significant sediment supply during the Late Cretaceous followin...

Stochastic velocity inversion of seismic reflection/refraction traveltime data for rift structure of the southwest Barents Sea
We present results from an active-source, onshore–offshore seismic reflection/refraction transect acquired as part of the PETROBAR project (Petroleum-related studies of the Barents Sea region). The 700km-long profile is oriented NW–SE, coincident with previously published multichannel seismic...