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

Abstract

a b s t r a c tIt has long been hypothesised that beds of highly organic mud or sapropels seen in marine sediment cores retrieved from the floor of the eastern Mediterranean accumulated during times of high Nile fluvial discharge. Our recent fieldwork in the valleys of the Blue Nile, the White Nile and the main Nile has for the first time revealed a sequence of extreme flood episodes synchronous with sapropel units S5 (124 kyr), S4 (102 kyr), S3 (81 kyr), S2 (55 kyr) and S1 (13.5e6.5 kyr). There are more weakly defined links with Nile floods and sapropel units S9 (240 kyr), S8 (217 kyr), S7 (195 kyr), S6 (172 kyr), but the dating error terms are too large to allow us to be too definite. During times of extreme floods over the past 125 kyr, wide distributary channels of the Blue Nile flowed across the Gezira alluvial fan in central Sudan and transported a bed load of sand and gravel into the lower White Nile valley. The sands were reworked by wind to form source-bordering dunes, all of which contain heavy minerals of Ethiopian provenance. These source-bordering dunes were active at 115e105 kyr, 60 kyr and 12e7 kyr, all times of extreme Blue Nile floods. The flood and dune sediments were dated using a combination of optically stimulated luminescence (OSL) and radiocarbon analyses. The Quaternary record of Nile floods discussed here shows a precessional signal and reflects episodes of stronger summer monsoon and more northerly seasonal movement of the ITCZ, linked to times of higher insolation in northern tropical latitudes. Progressive aggradation of Holocene Nile channels in northern Sudan has had a profound influence upon human settlement in the last 8 kyr.

International workshop on human occupations of the Nile Valley and neighboring regions between 75,000 and 15,000 years ago

“…Several models have been proposed, including a highly braided river with a much‐reduced discharge, a suspended‐load river, and that sand dunes dammed the Nile at specific places during the LGM, creating large lakes . Further south, in Sudan, correlation between Nile flows and sapropel S2 suggests a time of high water influx to the main Nile at ~55 ka, while during the LGM, both the White and the Blue Nile exhibit very low water discharge and high seasonality . In addition, oases in the Eastern Sahara have yielded evidence for habitability in the late Pleistocene, building a more complex picture than an “empty Desert” at that time …”

“…4 Further south, in Sudan, correlation between Nile flows and sapropel S2 suggests a time of high water influx to the main Nile at~55 ka, while during the LGM, both the White and the Blue Nile exhibit very low water discharge and high seasonality. 5 In addition, oases in the Eastern Sahara have yielded evidence for habitability in the late Pleistocene, building a more complex picture than an "empty Desert" at that time. 6 [8][9][10][11] North of the first cataract, few sites are known from the late MP and early UP, the majority of which are raw material procurement sites.…”

“…One main discussion point of the workshop was how to reconcile results from different fields. Most evidence for modern human Affiliations of participants: 1 University of Toronto (Canada), 2 University of Adelaide (Australia), 3 KU Leuven (Belgium), 4 University of Cassino (Italy), 5 Estonian Biocentre, Tartu (Estonia) and University of Padova (Italy), 6 Ronin Institute, 7 Ben-Gurion University, Beer Sheva (Israel) and University of Oxford (UK), 8 UMR CNRS 7194, Muséum national d'Histoire naturelle, Paris (France), 9 Institut National des Sciences de l'Archéologie et du Patrimoine (INSAP), Rabat (Morocco), 10 UMR 5199 PACEA, University of Bordeaux (France), 11 Polish Academy of Science (Poland), 12 University of Cambridge (UK), 13 The Hebrew University of Jerusalem (Israel), and 14 In particular, three main research avenues to enable new insights regarding population connectivity and dispersal within the region were pointed out, and these include the necessity to continue and organize new fieldwork in the Nile Valley and adjacent deserts, to refine the chronological resolution of human occupation and paleoenvironmental data in this area, and to conduct systematic comparisons of the archeological record between the different regions.…”

Holocene large lake development and desiccation: Changing habitats in the Kharga Basin of the Egyptian Sahara

“…The contrast in the upper parts of the sediments suggests that the two basins had already separated when these sediments were deposited and, as the western basin was smaller, it was more prone to desiccation and salination. In addition, the biodiversity and reddened sediment may reflect a contribution from the Nile via the Toshka overspill (Haynes, 1980; Haynes, Mehringer, & Zaghloul, 1979) during periods of higher Nile which are observed in the Northern Dongola Reach as persisting until 5.5 ky (Williams et al, 2015). Observations of the Khargan topography suggest that the two water‐bodies are separated when lake levels fall below around 140 m asl.…”

Holocene fluvial history of the Nile's west bank at ancient Thebes, Luxor, Egypt, and its relation with cultural dynamics and basin‐wide hydroclimatic variability

“…5000–2500 B.C.E. (Castañeda et al., ; deMenocal et al., ; Gasse, ; Hennekam, Jilbert, Schnetger, and de Lange, ; Krom, Stanley, Cliff, and Woodward, ; Woodward, Macklin et al, ). While the modern Nile system with its low‐sinuosity channel and mid‐channel bars is typical for the middle and late Holocene (Butzer, ; Said, ), there was a different Nile system with a more violent discharge regime, a braided channel pattern, and coarser deposits (with large sediment inputs from wadi systems; Woodward, Macklin et al, ) prior to this time.…”