The accumulation of nine heavy metals in fine-grained sediments from the mangrove fringed coast of French Guiana is evaluated.
The dynamic features of the South American tropical coastline, from the Amazon to the Orinoco Rivers, result in mangrove sediments being alternately submitted to phases of erosion and net sedimentation a few tens of years long.

This process influences the distribution of the heavy metals associated with these frequently re-mobilized deposits.
Sedimentary cores and mangrove plant samples were collected, at different seasons, in various swamps characterized by different properties (content of sedimentary organic matter, distance from sea water and fresh water). (lire la suite…)

Ocean Drilling Program (ODP) Sites 1257–1261 recovered thick sections of Upper Cretaceous–Eocene oceanic sediments on Demerara Rise off the east coast of Surinam and French Guiana, South America.

Paleomagnetic and rock magnetic measurements of ~800 minicores established a high-resolution composite magnetostratigraphy spanning most of the Maastrichtian–Eocene.

Magnetic behavior during demagnetization varied among lithologies, but thermal demagnetization steps >200°C were generally successful in removing present-day normal polarity overprints and a downward overprint induced during the ODP coring process. (lire la suite…)

Ce rapport présente les résultats obtenus à mi-étape de l’étude “Dynamique littorale et impacts socio-économiques en Guyane française. Approche par télédétection spatiale” faisant l’objet d’un contrat de consultance entre le CNES et l’IRD.

L’objet de cette consultance est de fournir au CNES, gestionnaire de l’accès au Port de Pariacabo à Kourou, les outils nécessaires pour une meilleure gestion des actions de dragage qu’il a en charge.

Le travail proposé comporte deux volets : (lire la suite…)

An unusual metamorphic diamond-bearing rock is part of the 2.11 Ga metavolcanics of the Lower Paramaca series in the Dachine area of the southern greenstone belt of French Guiana.
A mineral assemblage corresponding to greenschist facies metamorphism makes up the bulk of the host rock. Mantle-derived rninerals are a rninor component.

This study examines the characteristics of the host rock and defines an assemblage of the possible mantle-derived minerals using samples from outcrop, drill core and drill core concentrate from eight locations on the body. Special attention is given to the compositions of minerals that are used to forecast the diamond potential of tiraditional diamond deposits in order to determine if conventional diamond exploration techniques are valid at Dachine. (lire la suite…)

Sur un versant des terres hautes du Nord-Ouest de la Guyane, on compare les variations de caractères pédologiques simples et les rendements d’une culture mécanisée de manioc.

Les caractères pédologiques sont décrits, sur deux transects, à partir de sondages à la tarière; l’hydromorphie est également évaluée à l’aide d’un indice topographique. Les rendements (matière fraîche) en tubercules et parties aériennes consommables sont mesurés sur des placettes situées à proximité de chaque sondage. (lire la suite…)