Late Pleistocene to Holocene alluvial deposits of the Inaouène Valley and their paleoenvironmental significance (north Morocco)

This study investigates the paleoenvironmental changes and fluvial dynamics in the Inaouène River Valley of central northern Morocco over the last 22,000 years. Through comprehensive field study and radiocarbon dating of Upper Pleistocene and Holocene alluvial deposits, the research identifies six main alluvial units reflecting distinct phases of fluvial activity and environmental conditions. These phases include coarse gravel aggradation between ∼22 and 15 cal kaBP, indicating a braided channel system, followed by multiple fine-dominated alluviation phases occurring at ∼13, ∼10, ∼6–5, ∼3, ∼0.7–0.3, and ∼0.1-0 cal kaBP. The trunk channel evolved from a low-sinuosity wandering style in the Early-Middle Holocene to a high-sinuosity pattern in the Late Holocene. Periods of landscape stability, evidenced by soil formation, were dated around 0.3 and 0.8 cal kaBP, with additional episodes estimated just after ∼12 cal kaBP and around 3.8 cal kaBP. Notably, the study also uncovered evidence of significant human intervention during the Middle Holocene. A comparison with other archives enabled us to reconstruct late Pleistocene and Holocene palaeoenvironmental conditions on both regional and supraregional scales, linking specific stages of floodplain development to prevalent influencing factors. Emphasizing the fluvial system response, we present a cause-effect model that focuses on long-lasting climatic phases (e.g., Last Glacial Maximum, MIS2-MIS1 transition, African Humid Period) as well as sub-millennial to centennial Rapid Climate Changes, North Atlantic cooling events, and solar activity minima. Human intervention played a key role in the Inaouène's evolution during the Middle Holocene, as evidenced by clear anthropogenic markers found in the associated deposits. These findings not only contribute to our understanding of the area's geomorphological history but also highlight its significant archaeological potential, opening new avenues for interdisciplinary research in this understudied region. The study offers new insights into central northern Morocco's late Quaternary alluvial geochronology and paleoenvironmental evolution, aligning with regional findings and contributing to a broader understanding of climate-driven landscape changes and human-environment interactions across North Africa and the Mediterranean. • Late Pleistocene Inaouène shifted from a braided to a more stable channel. • Lateral deposits formed in parallel with an Early Holocene channel-deposits hiatus. • The hiatus persisted till Late Mid-Holocene, showing climate and Neolithic impact. • First discovery of an open-air site shows the archeological potential of the central part of the South Rifian Corridor. • Late Holocene Inaouène Valley experienced climate-driven buildups and incisions, coeval with channel pattern changes.