Geochemical and palynological analysis of Faiyum Lake sediments, Egypt: Implications for holocene paleoclimate

Abstract

During most of the Holocene, the Faiyum Depression in Middle Egypt was connected to the Nile River and contained an extensive freshwater lake. Geochemical analysis of a lacustrine sediment core (Qaru-9) from the depression provides evidence of changes in Nile sediment discharge related to changes in Ethiopian African Monsoon (EAM) precipitation, and allows us to reconstruct changes in Nile River runoff, vegetation and erosion in both the near and far catchment. Major and trace elements reveal significant changes in clastic sediment provenance, with sources oscillating between (i) a Blue/Atbara Nile fluvial contribution during the African Humid Period (AHP) and in the late Holocene (i.e. c. 10–7.5 & c.4–0 ka cal BP, respectively), (ii) a White Nile contribution between c. 7.5–4 ka cal BP with aeolian contributions and carbonate deposits occurring during local arid and wetter conditions, respectively. We also use geochemical data to assign variations in the paleowater properties of the Faiyum Lake (i.e. redox condition, paleosalinity and paleoproductivity) throughout the Holocene. Changes in pollen and algal remains in early to mid Holocene sediments confirm a deep freshwater lake prior to c. 10–8 ka cal BP but diminishing water levels after this period. The Faiyum Lake was a deep freshwater lake between 10 & 6 ka cal BP with fluctuating lake levels between 6–4 ka cal BP and during the late Holocene. In the later period, an abrupt drop in lake level occurred followed by increasing salinity as hydrological modifications occurred.