Nature and dynamics of North African humid and dry periods during the last 200,000 years documented in the clay fraction of Eastern Mediterranean deep-sea sediments

Abstract

The African monsoon system controlled the mobilisation and delivery of clay-sized sediment particles to the Eastern Mediterranean Sea in the late Quaternary. During African Humid Periods of the last 200 kyr, smectite-rich suspension load was provided by the Nile river and by palaeo-rivers discharging into the Gulf of Sirte. After the termination of the African Humid Periods, kaolinite- and palygorskite-rich clay was mobilised from desiccated soils, lake and river beds, and delivered in form of dust pulses to the Eastern Mediterranean Sea. Magnitude and abruptness of the dust pulses depend on the distance of the accumulation sites from the dust sources. Proximal sites experienced large amounts of dust from local sources, while more distal sites received dust from the wider Saharan region, documenting the time-transgressive termination of the humid periods. The strengths of individual dust pulses reflect the intensity of the preceding humid periods. Distinct droughts during the last glacial period can be associated with Heinrich events and are best documented at a semi-distal site, illustrating links between the African monsoon and the climate of the high-latitudes.