Thermochronology and U–Pb dating of detrital zircons from the Demerara Plateau (French Guiana‐Suriname): Implications for the provenance of the Early Cretaceous syn‐rift sedimentation

Abstract

AbstractThe provenance of Early Cretaceous sandstones dredged on the northern margin of the Demerara Plateau, offshore French Guiana and Suriname, reveals the sediment routing system that prevailed through the Equatorial Atlantic rifting. Fission‐track analysis and U–Pb dating of 310 and 111 detrital zircons, respectively, have been performed. Microfacies analysis and inherited cooling ages suggest that the sandstones were deposited in shallow marine environments during the Early Cretaceous, before the Late Albian drowning of the marginal plateau. Most of the U–Pb zircon crystallisation ages are comprised of between 700 and 600 Ma and are attributed to the Pan‐African‐Brasiliano orogeny. Statistical and chronological evidence suggest that the zircon fission‐track cooling ages were inherited from source materials. Triassic peak ages (>50% of the population) are attributed to the early phase of Central Atlantic rifting. One sample records a cooling phase at ca. 170 Ma, presumably following volcanic hotspot activity and the opening of the Central Atlantic Ocean. Two other samples record the rapid exhumation of the French Guiana transform margin during the Equatorial Atlantic rifting (127 ± 11 and 106 ± 8 Ma). We propose a source‐to‐sink model in which the Pan‐African‐Brasiliano basement of the margin was eroded as a result of flexural uplift along the French Guiana margin, and the detrital material funnelled in the Cacipore graben sustained the Early Cretaceous syn‐rift sedimentation on the marginal plateau.