Causal links between Nile floods and eastern Mediterranean sapropel formation during the past 125 kyr confirmed by OSL and radiocarbon dating of Blue and White Nile sediments

摘要: Abstract It has long been hypothesised that beds of highly organic mud or sapropels seen in marine sediment cores retrieved from the floor eastern Mediterranean accumulated during times high Nile fluvial discharge. Our recent fieldwork valleys Blue Nile, White and main for first time revealed a sequence extreme flood episodes synchronous with sapropel units S5 (124 kyr), S4 (102 kyr), S3 (81 kyr), S2 (55 kyr) S1 (13.5–6.5 kyr). There are more weakly defined links floods S9 (240 kyr), S8 (217 kyr), S7 (195 kyr), S6 (172 kyr), but dating error terms too large to allow us be definite. During over past 125 kyr, wide distributary channels flowed across Gezira alluvial fan central Sudan transported bed load sand gravel into lower valley. The sands were reworked by wind form source-bordering dunes, all which contain heavy minerals Ethiopian provenance. These dunes active at 115–105 kyr, 60 kyr 12–7 kyr, floods. dune sediments dated using combination optically stimulated luminescence (OSL) radiocarbon analyses. Quaternary record discussed here shows precessional signal reflects stronger summer monsoon northerly seasonal movement ITCZ, linked higher insolation northern tropical latitudes. Progressive aggradation Holocene had profound influence upon human settlement last 8 kyr.