A Franco-Djiboutian mission led by Marie Revel (member of the MARGES team of UMR GEOAZUR) and by Jessie Cauliez (UMR TRACES) is coming back from Lake Abhe where the mission "DESIRéE" from March 8 to 24, 2023 of the ANR NILAFAR program: Lake Abhe, an isolated, extreme environment (water with PH 10), today among the driest in the world.
Storms, force 7 winds, vehicles getting bogged down, exhausting heat, dust storm, technical breakdowns did not stop the team to carry out during 10 days in the Lake Abhe-Gobaad the coring of a 16 m long sedimentary sequence as well as geophysical studies: Fabien Arnaud, Jessie Cauliez, Eric Chaumillon, Bernard Fanget, Emmanuel Malet, Marie Revel, Université Nice Côte d'Azur, GéoAzur, Edytem, LIENs, TRACES, Université de la Rochelle, Université Toulouse Jean Jaurès, Mohamed Sahal and Mohamed Djama from ORREC -Observatoire de Recherche en Environnement et Climat.
"Désirée" owes its success to the expertise of the coring & seismic teams used to extreme field conditions as well as to
"Les Forces françaises stationnées à Djibouti et aux Hommes du 5ème Régiment Inter-Armes d’Outre-Mer" Convoyed by trucks, Puma helicopter, and more than 20 men worked to transport and install 3 tons of seismic and coring equipment in isolated and flooded territory, in degraded conditions
Objectives achieved:
Obtained 30 km of seismic profiles showing at an unprecedented resolution the lake sedimentation phases at the spatial scale of the lake for the last 20,000 years. These profiles, which allowed the selection of the long core site, show that the sedimentation, mainly resulting from the flood deposits of the Awash and Gobaad rivers, was set up in about ten successive phases. These changes suggest a strong potential for recording past hydro-climatic and environmental changes
Collection of the 2 longest cores ever extracted in the Horn of Africa in an aquatic environment: 16 m long, which should cover the last 20,000 years of hydro-climatic history in East Africa.
These studies will provide the paleoenvironmental and hydro-climatic framework in which the hunter-gatherer societies and the first pastoralist communities analyzed for more than 30 years within the framework of the archaeological and paleoclimatological program PSPCA First Production Societies in the Horn of Africa of the MEAE which is being deployed in Djibouti (dir. Jessie Cauliez), VaporAfar in Ethiopia (dir. L. Khalidi) and Late Stone Sequence in Ethiopia (dir. C. Ménard). The originality of the ANR NILAFAR is the complementarity between the approach in geosciences, archaeology, geomorphology & climate modeling.
Extraction of short cores that will count the history of the last centuries in the African Rift region, at very high resolution and allow to reflect on the evolutions and the disruption of the current and future climate...thus responding to current ecological and societal issues that feed the international debates
The future laboratory analysis of molecular biomarkers - GDGTs - Glycerol Dialkyl Glycerol Tetraether lipids - of bacteria trapped in the sediment of Lake Abhe should allow to reconstruct past variations in temperature and precipitation of this region of the Horn of Africa. The chemical composition of the GDGTs responds to changes in environmental conditions and thus (coupled with Nd/Li isotope composition of terrigenous particles) will constitute markers of the flood history of the Awash and Gobaad rivers and weathering intensity in the Gobaad/Afar basins composed by stratoid basalts and Quaternary sediments. These reconstructions will then be compared to global climate modeling and more regional flow reconstructions of the Awash.
« Désirée » est une mission portée par l’ORREC le nouvel Observatoire Régional de l’Est Africain consacré à l’étude de l’Environnement et du Climat basé à Djibouti (MENSUR CERD) dirigé par Moussa Medhi secondé par David Williamson. Nous remercions Mr Le Ministre de l'Enseignement supérieur et la Recherche de DJibouti, Nabil Mohamed Ahmed , ainsi que le directeur du CERD, Mohamed Jalludin, pour avoir facilité l'obtention des autorisations, l’IFD et l’Ambassade de France, le groupe Marill, Safar Voyage, la Ferme du Neem, l’Association de Développement des Jardins d’As Eyla, le Kempinski pour leur soutien et leur amitié.
