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Nile River sediment fluctuations over the past 7000 yr and their key role in sapropel development

Michael D. Krom, Jean-Daniel Stanley, Robert A. Cliff and Jamie C. Woodward
Nile River sediment fluctuations over the past 7000 yr and their key role in sapropel development
Geology (Boulder) (January 2002) 30 (1): 71-74


The provenance pattern of Nile River sediments can be used as a proxy for paleoclimatic changes in East Africa. The (super 87) Sr/ (super 86) Sr ratios are particularly appropriate for such provenance investigations, because the White Nile drains predominantly crystalline basement rocks, whereas the Blue Nile and Atbara flow off the Ethiopian Highlands, which consist of Tertiary volcanic rocks. A high-resolution profile of (super 87) Sr/ (super 86) Sr and Ti/Al ratios from a well-dated core in the Nile Delta shows a close correspondence with known changes in Nile flow over the past 7000 yr. At times of higher river flow there was markedly decreased input of Blue Nile-derived and total sediment. This change was caused by northward movement of the Inter Tropical Convergence Zone, resulting in increased vegetative cover in the Ethiopian Highlands due to higher rainfall and a longer wet season. This inverse relationship between Nile River flow and sediment flux may have had important implications in the development of agricultural technology in ancient Egypt. The marked minimum in (super 87) Sr/ (super 86) Sr at 4200-4500 yr B.P. is coincident with the end of the Old Kingdom in Egypt and provides independent evidence that demise of the Old Kingdom might have been associated with an extended period of catastrophic low floods. During the Quaternary and late Neogene, there was periodic deposition of organic-rich sediments (sapropels) in the eastern Mediterranean that represent important indicators of major environmental change. Evidence from the Ti/Al ratio suggests that the pattern of erosion and sediment supply from the Nile catchment observed in this study also occurred throughout much of the Neogene and Quaternary. The reduced inputs of Blue Nile sediment during times of sapropel formation contributed to the increased primary productivity by reducing the amount of phosphate removed on particles and to the observed change to N limitation in the eastern Mediterranean, which are important characteristics of sapropel deposition.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 30
Serial Issue: 1
Title: Nile River sediment fluctuations over the past 7000 yr and their key role in sapropel development
Affiliation: University of Leeds, School of Earth Sciences, Leeds, United Kingdom
Pages: 71-74
Published: 200201
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 30
Accession Number: 2002-012625
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
N30°10'00" - N31°40'00", E29°49'60" - E32°19'60"
N22°00'00" - N31°00'00", E31°00'00" - E37°00'00"
Secondary Affiliation: Smithsonian Institution, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200205
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