Seminar by Geoffrey Aertgeerts (BRGM) – “Geoscientific diversity in French Guiana: what issues and possible solutions in this region with strong environmental and regulatory constraints”

French Guiana is the only French overseas territory of South America and is, thus, under French regulation. To a geological point of view, French Guiana belongs to the Guiana shield which extent from Venezuela to Brazil and was structured during the transamazonian orogeny (2.5-1.9 Ga). French Guiana is composed of greenstones belts, of large TTG batholites, of orogenic granites, and to a lesser extent of intracontinental detrital basins. Since around 30 Ma, French Guiana undergoes a tropical to equatorial climate responsible of a strong lateritic and bauxitic weathering (up to 100 m thick) that does not exist in other French regions and that strongly constraints geoscientific studies. Almost the entire French Guiana is covered by the Amazonian Forest that strongly limits field trips, field logistic and field observations. However, requirements in water resources, waste stockage, land planning and protection of the population against natural hazards are determined under the same regulations than in France and geoscientific studies for public policies have to follow strict methodologies that are not always adapted or possible in French Guiana. In this context, the presentation will focus on two studies of the BRGM of Cayenne where scientific methods classically used in hexagonal France were simplified or improved to better fit with the local constraints. The first study will present the development of a new method of landslide mapping, and the second one will focus on waste stockage in an isolated Amerindian village.