5.9 kiloyear event

5.9 kiloyear event

The 5.9 kiloyear event was one of the most intense aridification events during the Holocene. It ended the Neolithic Subpluvial and probably initiated the desiccation of the Sahara desert. Thus, it also triggered world-wide migration to river valleys, e.g. from central North Africa to the Nile valley, what eventually led to the emergence of first complex, highly organised, state-level societies in the 4th millennium BC. cite journal | last = Brooks | first = Nick | authorlink = | coauthors = | year = 2006 | month = | title = Cultural responses to aridity in the Middle Holocene and increased social complexity | journal = Quaternary International | volume = 151 | issue = 1 | pages = 29–49 | doi = 10.1016/j.quaint.2006.01.013 | url = | accessdate = | quote = ]

A model by Claussen "et al." (1999) suggested rapid desertification associated with vegetation atmosphere interactions following the 5.9 kiloyear cooling event (Bond event 4). cite journal | last = Claussen | first = Mark | authorlink = | coauthors = "et al." | year = 1999 | month = | title = Simulation of an Abrupt Change in Saharan Vegetation in the Mid-Holocene | journal = Geophysical Research Letters | volume = 26| issue = 14 | pages = 2037–2040 | doi = | url = http://www.agu.org/pubs/crossref/1999/1999GL900494.shtml | accessdate = | quote = ]

Bond "et at." (1997) identified a North Atlantic cooling episode at 5,900 BP from ice-rafted debris, as well as other such now called Bond events that indicate the existence of a quasiperiodic cycle of Atlantic cooling events, which occur approximately every 1500 years.cite journal| author = Bond, G. | coauthors = "et al." | url=http://rivernet.ncsu.edu/courselocker/PaleoClimate/Bond%20et%20al.,%201997%20Millenial%20Scale%20Holocene%20Change.pdf | year = 1997 | title = A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates | journal = Science | volume = 278 | issue = 5341 | pages = 1257-1266 | doi = 10.1126/science.278.5341.1257 ] For some reason, all of the earlier of these arid events (including the 8.2 kiloyear event) were followed by recovery, as attested by the wealth of evidence of humid conditions in the Sahara between 10,000 and 6,000 BP.cite book |title=Third Millennium BC Climate Change and Old World Collapse |chapter=Holocene climate change and man in the present day Sahara desert |last=Petit-Maire |first=N. |authorlink= |coauthors= Beufort, L.; Page, N. |editor=Nüzhet Dalfes, H.; Kukla, G.; Weiss, H. (Eds.) |year=1997 |publisher=Springer |location=Berlin |isbn=3540618929 |pages=297–308 ] However, it appears that the 5.9 kiloyear event was followed by a partial recovery at best, with accelerated desiccation in the millennium that followed. For example, Cremaschi (1998) describes evidence of rapid aridification in Tadrart Acacus of southwestern Libya, in the form of increased aeolian erosion, sand incursions and the collapse of the roofs of rock shelters.cite book |title=Wadi Teshuinat: Palaeoenvironment and prehistory in south-western Fezzan(Libyan Sahara) |chapter=Late Quaternary geological evidence for environmental changes in south-western Fezzan (Libyan Sahara) |last=Cremaschi |first=M. |authorlink= |editor=Cremaschi, M.; Di Lernia, S. (Eds.) |year=1998 |publisher=Ed. All' Insegna del Giglio |location=Firenze |isbn=8878141445 |pages=13–47 ]

In the Middle East the 5.9 kiloyear event led to the abrupt end of the Ubaid period. cite journal | last = Parker | first = Adrian G. | authorlink = | coauthors = "et al." | year = 2006 | month = | title = A record of Holocene climate change from lake geochemical analyses in southeastern Arabia | journal = Quaternary Research | volume = 66 | issue = 3 | pages = 465–476 | doi = 10.1016/j.yqres.2006.07.001 | url = http://www.gulfnexus.org/articles/geo/2006a%20Parker%20et%20al.pdf | accessdate = | quote = ]

The 5.9 kiloyear event was also recorded as a cold event in the Erhai Lake (China) sediments. cite journal | author = Zhou Jing | authorlink = | coauthors = Wang Sumin; Yang Guishan; Xiao Haifeng | year = 2007 | month = | title = Younger Dryas Event and Cold Events in Early-Mid Holocene: Record from the sediment of Erhai Lake | journal = Advances in Climate Change Research | volume = 3 | issue = Suppl. | pages = 1673–1719 | id = | url = http://www.climatechange.cn/qikan/manage/wenzhang/08.pdf | accessdate = | quote = ]


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