Description: The relationship of sea-level changes and short-term climatic changes with turbidite deposition is poorly documented, although the mechanisms of gravity-driven sediment transport in submarine canyons during sea-level changes have been reported from many regions. This study focuses on the activity of the Dakar Canyon off southern Senegal in response to major glacial/interglacial sea-level shifts and variability in the NW-African continental climate. The sedimentary record from the canyon allows us to determine the timing of turbidite events and, on the basis of XRF-scanning element data, we have identified the climate signal at a sub-millennial time scale from the surrounding hemipelagic sediments. Over the late Quaternary the highest frequency in turbidite activity in the Dakar Canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea-level rise. However, episodic turbidite events coincide with the timing of Heinrich events in the North Atlantic. During these times continental climate has changed rapidly, with evidence for higher dust supply over NW Africa which has fed turbidity currents. Increased aridity and enhanced wind strength in the southern Saharan–Sahelian zone may have provided a source for this dust.

Description: Highlights • Flooding events recorded in a shallow marine sediment core over the last 5800 years • High fine-grained sediment inputs under flood events and humid conditions • Low input of terrigenous sediments under dry conditions • NAO influenced sediment supply during the last 500 years at centennial scales • Increase flooding events during the LIA along the Atlantic Iberian Peninsula margin Abstract Sedimentological, geochemical and benthic foraminiferal proxies were used to interpret changes of depositional environments in a mud entrapment inside the Guadiana River paleo-valley, northern Gulf of Cadiz, to understand the temporal variability of fluvial flooding events and to detect patterns of latitudinal climatic variability in western Iberia. The period between ca. 5800 and ca. 1250 cal yr BP was characterized by slowly accumulating coarse-grained sediments, high content of biogenic sand components, and high abundances of shallow-water benthic foraminiferal species. After ca. 1250 cal yr BP, the sedimentary environment was dominated by fine-grained sediments, with high abundances of opportunistic benthic foraminiferal species and successful colonizers, and high values of geochemical ratios indicative of enhanced terrigenous supply. Sedimentation rates increased drastically over the last ca. 500 years. The genesis of these environments was mainly driven by the variable frequency of fluvial flooding events driven by the regional climate variability. Low terrigenous sediment input under dry conditions prevailed in the older sedimentary unit. Flood frequency and terrigenous sediment supply increased during the younger unit. The variability of the North Atlantic Oscillation at centennial scales highly influenced the sediment supply during the last ca. 500 years, with high terrigenous supply during negative NAO conditions. Our results corroborate an N-S gradient along the Atlantic Iberia during middle and late Holocene, with more humid conditions in the northwestern and drier conditions towards the southeast. The gradient weakened over the past ca. 500 years, with increased rainfalls and flood events during the Little Ice Age.

Description: Continental shelves represent areas of highest economical and ecological importance. Nevertheless, these sedimentary systems remainpoorly understood due to a complex interplay of various factors and processeswhich results in highly individual construction schemes. Previous studies of sedimentary shelf systems have mainly focused on a limited number of cores, retrieved from Holocene fine-grained depocentres. As such, the relation between shelf architecture and sedimentary history remains largely obscure. Here,we present newdata fromthe NW Iberian shelf comprising shallow-seismic profiles, a large number of sediment cores, and an extended set of radiocarbon dates to reveal the Late Quaternary evolution of a low-accumulation shelf system in detail. OntheNWIberian shelf, threemain seismic units are identified. These overly a prominent erosional unconformity on top of the basement. The lowermost Unit 1 is composed of maximal 75-m thick, Late Tertiary to Pleistocene deposits. The youngest sediments of this unit are related to the last glacial sea-level fall. Unit 2 was controlled by the deglacial sea-level rise and shows a maximumthickness of 15 m. Finally, Unit 3 comprises deposits related to the late stage of sea-level rise and the modern sea-level highstand with a thickness of 4 m in mid-shelf position. Two pronounced seismic reflectors separate these main units from each other. Their origin is related to (1) exposure and ravinement processes during lower sea level, and (2) to reworking and re-deposition of coarse sediments during subsequent sea-level rise. According to the sediment core ground-truthing, sediments of the Late Tertiary to Pleistocene unit predominantly display homogenous fine sands with exceptional occurrences of palaeosols that indicate an ancient exposure surface. Fine sands which were deposited in the run of the last sea-level rise show a time-transgressive retrogradational development. The seismic reflectors, bounding the individual units, appear in the cores as 0.1 to 1-m thick deposits consisting either of shell gravels or siliceous coarse sands with gravels. The modern sea-level highstand stage is characterised by zonal deposition of mud forming a mud belt in mid-shelf position, and sediment starvation on outer shelf zones. Radiocarbon ages indicate that this mud beltwas the main depocentre for river-supplied fine material on the NWIberian shelf at least over the past 5.32 ka BP. The initial onset of this depocentre is proposed to be related to a shift in the balance between rate of sea-level rise and amount of terrigenous sediment supply. Various other stratigraphical shelf reconstructions reveal analogies in architecturewhich indicate that timing and shaping of the individual units on low-accumulation shelves is fundamentally controlled by eustatic sea-level changes. Other factors of local importance such as differential elevation of the basement and the presence of morphological barriers formed by rocky outcrops on the seafloor have additionally modifying influence on the sedimentary processes.