The NILE & AFAR areas: hydrological change sensitivity and impact on past human adaptation since 20,000 years – NILAFAR

Task 1 Paleosciences: aims to reconstruct hydrological fluctuations in the Afar area at centennial-millennial resolution over the last 20,000 years using Innovative tracers such as Delta2Hwax, GDGT (Glycerol Dialkyl Glycerol Tetraethers or GDGTs) and diatom assemblages. Also, neodymium isotope composition (143Nd/144Nd) which can evaluate the provenance of lake sediment will be coupled with lithium isotopes (delta7Li), which trace the intensity of weathering and clay neoformation in soils.

Task 3 Archeology
task 3 will excavate and date chrono-spatially unrepresented human occupation sequences with the aim of reconstituting paleoeconomy and cultural change over the last 20,000 years through focused archaeological investigation in the Afar (Ethiopia, Djibouti) and the Central Ethiopian Rift Valley. The project focuses particularly on the persistence and decline of hunter-gatherer communities and the emergence of pastoralism. The multidisciplinary NILAFAR project is largely based on the work of three complementary archaeological programs in the Afar and the Central Rift Valley
VAPOR-Afar directed by Lamya Khalidi,
PSPCA directed by Jessie Cauliez
LSA Sequence directed by Clément Ménard.
Task 4 Geomorphology aims to reconstruct regional paleolandscapes through geomorphological surveys of the Gamari, Afambo, Abhe and Ziway/Shala paleolake basins and shorelines and dating of environmental archives (stromatolites, diatomites, paleosoils, aeolian deposits, etc.). Reconstruction of lake level fluctuations will provide high-resolution information on environmental change, time-range and relationship to human settlement patterns.

Task 2 Modeling
The combination of climate model simulations (from the Paleoclimate Modeling Intercomparison Project PMIP and IPSL models) and hydrological model simulations (a rainfall-runoff model – previously calibrated on the observed period using available discharge series) will be used to investigate the different factors and important thresholds controlling the hydrology in Afar, in terms of precipitation regimes (humid and dry periods such as AHP and LGM, respectively), source of the moisture flux (from Atlantic or Indian oceans) on the region, and length of critical dry episodes (such as HS, YD, 8.2, 4.2ka)

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(invited article, accepted) Mologni C., Revel M., Bastian L., Bayon G., Bosch D., Khalidi L., Vigier N. 2022. Enhanced continental weathering (d7Li) during the rise of East African complex societies: an early large-scale anthropogenic forcing? Comptes Rendus de Géoscience.
• Coudert L., Dufour E., Bruxelles L., Gosselin M., Lesur J., Mologni C., Cauliez J., en cours de correction, Hydrology of the Lake Abhe (Ethiopia-Djibouti) during the Late Holocene and its use by humans: contribution of d18O analyses of fish otoliths, Palaeogeography, Palaeoclimatology, Palaeoecology
• Crevecoeur I., Bayle, P., Matu M., Pearson O., Paleoanthropology and population processes since the MIS 3 in North-east Africa, a regional synthesis. In : Lesur et al., (Eds.), Du Big dry à l’Holocène en Afrique de l’est et au-delà, Bulletin de la Société Préhistorique Française (Accepté).
• Mologni C., Bruxelles L., Schuster M., Davtian G., Ménard C., Orange F., Doubre C., Cauliez J. , Berhane Taezaz H., Revel M., Khalidi L. 2021. Holocene East African monsoonal variations recorded in wav-dominated clastic paleo-shorelines of Lake Abhe, Central Afar region (Ethiopia & Djibouti), Geomorphology, Vol. 391, doi.org/10.1016/j.geomorph.2021.107896
• C. Darles, L. Khalidi, M. Arbach (Eds.) (2021). Contacts Between South Arabia and the Horn of Africa, From the Bronze Age to Islam. In Honor of Rémy Audouin. Sites et Cités d'Afrique Series. F.-X. Fauvelle-Aymar, F. Bon (series Eds.). Toulouse: Presses universitaires du midi. 343 pp.
• Cauliez J., Hérouin S., Gutherz X., Aden Asma Youssouf, Alarashi H., Bruxelles L., Coudert L., Diaz A., Khalidi L., Lesur J., Marquebieille Benjamin, Matu M., Osman Ali Ibrahim, Thouvenot Y., Zazzo A. (2021). Monumentalisme funéraire et premières sociétés de production dans la Corne de l’Afrique. Le monument à double couronne d’Antakari 3 en République de Djibouti (région d’As Eyla, District de Dikhil). In Mégalithismes et monumentalismes funéraires : passé, présent, futur. V. Ard, E. Mens, M. Gandelin (eds.), Leiden: Sidestone press, pp. 319-351.

The NILAFAR program proposes to study the impact of hydrological fluctuations on societies in NE Africa over the last 20,000 years and in particular on the development of pastoralism. NILAFAR also aims to better understand the climatic mechanisms at the origin of the fluctuation intensity of the African monsoon (external forcing and internal feedbacks of the climate system), and at the origin of short hyperarid episodes. During the African Humid Period (AHP) these episodes saw the retraction or dissemination of particularly mobile human groups. In an environment that may have been as limiting as it was stimulating due to the alternance of these hyperarid and wet phases, populations innovated using new economic strategies, shifting from a predation to a production economy. NILAFAR proposes to explore the correlation between paleo-hydrological regimes and the evolution of these anthroposystems in the Afar valley in Ethiopia and Djibouti. The AHP will be revisited using innovative inorganic and organic tools that allow a quantification of hydrological variations of lakes and chemical alteration of Ethiopian soils at high temporal resolution (~100 years). In this context, we will study the Afambo, Gamari and Abhe Lakes and their watersheds as they have high-resolution records of major monsoon and environmental changes that occurred from the late Pleistocene (pre- 11.7 ka) to the Early Holocene (pre- Anthropocene).
The originality of the project is its disciplinary and human synergy that combines different fieldwork approaches in the Afar region (archaeology, coring of Abhe basin lake sediment, geomorphology, cartography), a reconstruction of human settlement patterns and paleoeconomy by combining the study of morphosedimentary archives and archaeomaterials, hydro-climatic modelling, and a reconstruction of hydrological fluctuations by coupling innovative (lithium isotopes, biomarkers) and classical analytical tools (neodymium isotopes, diatoms and hydrochemical transfer functions). The establishment of robust age models, both for lake and soil archives and for successive human occupation sequences will be a priority as our preliminary results are very promising. Large-scale climate simulations will be used to study the mechanisms of monsoon change during the last deglaciation/Holocene, and a rain-flow model will be developed to better understand the changes in the flow of the Awash River which drains this zone and also in the flow of the Blue Nile. These models, which have been tested on a large number of past climates and hydrologies, will act as excellent tools to predict future hydrological and climatic variations at the scale of this region. Finally, Human-Ecosystem-Climate coevolution will be explored over this wide chronological sequence.
The ultimate objective of this project is to propose solutions for populations to better adapt to the agro-pastoral and water resource challenges of our societies, of first order in countries such as Ethiopia and Djibouti which are facing infrastructure development. We will train students and future researchers to understand global warming mechanisms and to cautiously predict the future of arid regions. This transmission of knowledge will take place over four years with a request for two post-doctoral positions in archeology and modelling and a PhD thesis for the acquisition of innovative data. This project will also provide an opportunity to strengthen the training of Ethiopian students in the field and in geochemistry through joint university courses.