The Mediterranean area is particularly sensitive to environmental changes. In Morocco, research undertaken over the past ten years has shown that continental sedimentary archives are useful to document Holocene environmental and climatic variability. However, palaeoenvironmental reconstruction using non-marine molluscs is in an early stage of research. This paper aims to present a new chronostratigraphical and malacological analysis from a Middle-Holocene and Upper Pleistocene tufa sequence in the Middle Atlas (Aït-Said-ou-Idder). Results highlight that the lower part of the sequence is dated from the Upper Pleistocene which corresponds to a fluvio-paludal model of deposition. Radiocarbon dates assign the upper part of the sequence to the Middle Holocene. During the Pleistocene phase, the environment is a reed swamp that turns to permanent body water. During the Middle Holocene, three main environmental phases have been identified. Between 6600 and 6100 cal BP, a mesophilic environment is characterised by open and dry areas with some paludal zone. Between 6100 and 5600 cal BP, a durable marshland developed. Between 5600 and 4600 cal BP, the paludal zone tended to disappear while an open and sclerophyllous environment developed. The malacological study provides important elements to the construction of a Holocene malacological framework in Morocco initiated at Blirh (Upper Moulouya). Both records identify a drastic switch to environmental aridification at the end of the Middle Holocene. By recording at the same time local evolution and regional trends and events, Aït Said ou Idder results provide material to understand environmental variability in north-eastern Morocco.

The Early–Mid Holocene transition is a period of profound changes in climatic mechanisms and hydrological features in Europe and North Africa. The melting of the Laurentide ice sheet led to an oceanic and atmospheric reorganisation in the North Atlantic, while the Mediterranean underwent a major hydrological shift. The impacts on Mediterranean rivers remain unclear, as there are few records documenting responses to the 8.2 ka event (the main Holocene climatic degradation). We present a fluvial record from Eastern Morocco documenting detailed hydrological variations from 8200 to 7500 cal. BP and their climatic forcing. A major hydrogeomorphic evolution of the Charef River occurred at that time, marked by two major incision stages close in time, under hyper-arid conditions at 8200 and ca. 7500 cal. BP. The impacts of these phenomena on the alluvial plains and associated archaeological records during Neolithisation, a major process in human history, currently remain unidentified. This new record sheds light on the fluvial response to the 8.2 ka event in North Africa and why other records are missing. We also bring new insights into the hydrological disruption at the Early–Mid Holocene transition, which was driven by the end of deglaciation combined with insolation and solar forcing. Furthermore, centennial solar variability may have paced river activity in the Moulouya basin and arid regions of North Africa.

Abstract. In the last few decades, multidisciplinary research on calcareous tufas as palaeoenvironmental and palaeoclimatic records has intensively grown, which has provided an increasing number of well-documented sites. Consequently, inter-site comparisons and regional- to continental-scale reviews have developed, discussing the link between tufa distribution and climate or providing diachronic comparisons of climatic and environmental conditions prevailing during Quaternary interglacials (and interstadials). This paper proposes such a review for the southeastern Mediterranean area, including new dating and isotopic data from Aït Said ou Idder (northern Morocco) to be compared with available regional data, in order to discuss the intensity of some humid periods of the last 125 kyr. According to several radiocarbon and U–Th dates, three chronological phases are indeed identified at Aït Said ou Idder: the Holocene, the Dansgaard–Oeschger (D–O) interstadial 8 and the Marine Isotopic Stage (MIS) 5e. Similarly, other tufa deposits from both Morocco and southern Spain (mostly Andalusia) appear to have preferentially developed during interglacial or interstadial periods, marked by maximal developments of the Mediterranean forest as reported in the palynological records from regional marine cores. Furthermore, isotopic data (δ18O and δ13C) from Aït Said ou Idder (and from other southeastern Mediterranean tufa deposits where available) suggest no significant difference in terms of temperature or air mass circulation between the Holocene, D–O 8 and MIS 5e. In terms of humidity conditions, no evidence of strong aridity is recorded even if D–O 8 appears drier than both interglacials. Conditions seems slightly wetter during the Holocene than during MIS 5e, but δ13C values at Aït Said ou Idder could also reflect strong differences in the seasonality of these interglacials. We demonstrate that calcareous tufa deposits have promising potential for discussing, in both space and time, the climate variability in the southeastern Mediterranean area, but new investigations, including dating and stable isotopes, are required to accurately feed such discussions.