Pleistocene Ecosystems of French Guiana: Benthic Foraminifera as Key Indicators

• Applicant: Professor Dr. Martin Langer
• Subject Area: Palaeontology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559945700

The Earth has experienced drastic environmental changes during the last 2.6 Ma (Pleistocene–Holocene epochs, Quaternary period), under contrasted interglacial-glacial alternations at a global scale triggered by orbital parameters. Although widely investigated through the fossil record, the response of organisms and ecosystems to these changes in terms of dynamics (extinction/dispersals/turnovers) remains poorly understood, notably due to the virtual lack of fossils and related proxies. The Guianas comprise a vast territory (ca. 2.5 million-km2) near the Equator in South America. Today, this region shelters high levels of taxonomic diversity in both terrestrial and aquatic ecosystems, but almost nothing is known about its past biodiversity. Indeed, Guianese coastal areas are covered by mangrove vegetation and tidally-influenced river banks whilst herbaceous swamps and savannas are followed by marsh and evergreen woodlands more inland. This dense vegetation hampers access to potential fossil-yielding outcrops. Guianese coasts are further impacted by a huge flux of surface waters of Andean-Amazonian origin. This northwestward flux strongly structures the composition of recent tropical Western Atlantic biotic communities, without a clue about its role in the past. Until recently, French Guiana (FG) was a terra incognita for paleontologists and paleobiologists and the sedimentary archives are much reduced in terms of surface area, thickness, and available outcrops. The Guianese coastal plains, however, present a Pliocene–Quaternary coastal series and comprise Late-Middle-Early Pleistocene and Holocene sedimentary sequences. Despite their paleontological potential and until very recently, however, these coastal formations had not yielded any fossil record yet, and their deposition chronologies remain debated. This project aims to unravel the composition, dynamics and biogeography of French Guiana’s marine foraminiferal biotas, with a focus on the Last interglacial (LIG)–Early Holocene interval (128–8 ka), through the study of coastal series. The goal is to reconstruct the environmental conditions along the coast of French Guiana prior to the appearance of humans in the region, and how the change from marine to a savannah-like palaeo-landscape occurred with the onset of the last glacial period (110-50 ka). Foraminiferal data will be analyzed from new fieldwork localities and will provide key information on the first Pleistocene ecosystems to be documented in FG, and constraints about their spatiotemporal dynamics. These ancient ecosystems, which predate human arrival in the Guianas, open an unprecedented window on a timespan devoid of any anthropogenic footprint at a regional scale. Moreover, the LIG (128–116 ka) is an accurate analog for current climate change, both in terms of sea-level rise and warming speed, which allows for regional projections as for 2100 regarding landscapes and taxonomic richness.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Pierre-Olivier Antoine