Flood frequencies reveal Holocene rapid climate changes (Lower Moulouya River, northeastern Morocco)

Abstract

Current high-resolution palaeoenvironmental records reveal short-term Holocene coolings. One of these major Holocene rapid climate changes occurred between 3.2 and 2.7 cal. ka BP. The sensitivity of river systems vis-à-vis slight and short-term Holocene climatic variations is a subject of controversy in the scientific community. In this paper, we present a 4.0 to 1.4 cal ka BP palaeoflood record from the Lower Moulouya River (northeastern Morocco) to demonstrate the high sensitivity of semiarid rivers in the southwestern Mediterranean towards Holocene environmental changes. The Lower Moulouya flood deposits are characterised by thick, well-stratified, predominantly clayey to silty overbank fine sediments. These cohesive sediments show evidence of excellent preservation conditions against fluvial erosion and contain a continuous record of mid to late Holocene flood sequences. The Moulouya palaeoflood record can be interpreted in the context of regional and global high-resolution proxy data, revealing a strong coupling with Holocene rapid climate changes. The centennial-scale Moulouya palaeohydrological history will be discussed with palaeoenvironmental data from the same record (palaeomagnetics, sedimentary charcoal record, anthracological analyses, snail analyses) to generate new ideas about the mid to late Holocene hydrological cycle in the southwestern Mediterranean. The deduced features of pronounced Lower Moulouya flooding and the decreased fire recurrence during Holocene cooling remain somewhat inconsistent with the interpretation of other palaeohydrological and paleaoecological records from the southwestern Mediterranean. However, enhanced Lower Moulouya flood frequencies between 3.2 and 2.7 cal. ka BP agree with increased floodplain aggradation in other major river systems of Mediterranean North Africa.

Holocene environmental change and human impact in NE Morocco: Palaeobotanical evidence from Ifri Oudadane

“…BP (Early Neolithic A and B), wild olive and mastic continue to be abundant as well as other elements of the xerothermophilous macchia and the riparian forest, reflecting a humid and warm climate. These data agree with the anthracological analysis carried out in the Djamila profile at the Lower Moulouya river (Linstädter and Zielhofer, 2010;Zielhofer et al, 2010), that shows the dominance of Olea and Pistacia records between c. 7.4 and 6.6 cal. BP.…”

Anthropogenic and climatic impact on Holocene sediment dynamics in SE Spain: A review

“…Under drier conditions, the reduced vegetation cover enhances the erosion susceptibility of the soil surface, and triggers rapid sediment transport to the stream network (e.g. Faust et al, 2004;Sancho et al, 2008;Zielhofer et al, 2010). Records from Sicilia also show synchronous changes between fluvial activity and climate shifts but show an opposite pattern (Fig.…”

Western Mediterranean hydro-climatic consequences of Holocene ice-rafted debris (Bond) events

“…Fluvial geomorphologists identify Holocene flood intervals that chronologically match with peaks in the ice-rafted debris record. This is the case for Western Mediterranean fluvial records in Morocco and Tunisia (Faust et al, 2004;Zielhofer et al, 2010) but also for fluvial records in Western Mediterranean Europe (Benito et al, 2008(Benito et al, , 2015aWolf et al, 2013). Furthermore, Western Mediterranean proxy data for prehistoric human occupation, such as 14 C cumulative probability plots from archaeological databases, show a probable linkage with ice-rafted debris events Linstädter, 2016).…”