High-resolution sedimentary record in the eastern Mediterranean shelf shows reduced Nile-derived mud after the Little Ice Age (1830 CE)

Abstract

Chemical, sedimentological and micropaleontological records were used to track recent climatic and ecological events recorded in eastern Mediterranean shelf sediments. By studying a high-resolution record of well-dated sediment from the Israeli shelf, natural and anthropogenic influence during the past 270 years were differentiated and pinpointed to major events.

The most prominent changes occurred in sediment source at the end of the Little Ice Age (LIA), in 1830–1840 CE. Coarse, quartzose sand comprised only 5% of the sediment during the LIA, and increased significantly after the LIA to levels of up to 15%. There was a further increase in the coarse, quartzose content to >20% following the damming of the Nile River (Aswan High Dam, in 1964), continuing the earlier post-LIA increase.

The geochemical data suggests a shift in the composition of the finer-grained sediments at the end of the LIA. During the LIA, clay-rich sediments were found to have lower levels of K₂O and higher levels of Ni compared to sediments post-LIA. These likely indicate a change in the source of sediments to the eastern Mediterranean shelf, shifting from a dominance of Nile-derived sediments and Nile Delta soils during the LIA, to more Saharan-derived, fine-grained dust and coarse-grained quartzose sands in the post-LIA period. The prevalence of Nile-derived sediments during the LIA suggests wetter conditions in coastal East Africa during that time period, as opposed to post-LIA.

The foraminiferal data also indicate a shift at the end of the LIA, mainly in group composition and abundance. A major increase in miliolid shell-type abundances after the LIA, aligns with a transition to warmer temperatures post-LIA. An additional increase is detected in species richness and abundance after the damming of the Nile River. However, this is superimposed on the ongoing increase since the LIA termination.