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Late Quaternary environments of the dry tropics and subtropics Ô North Africa Ô Arabia - India Ô Australia Ô South Africa Ô South America

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  • Late Quaternary environments of the dry tropics and subtropics North Africa Arabia - India Australia South Africa South America

  • Saharan dustIn the journal of his voyage aboard HMS Beagle in 1833, Darwin commented on the atmospheric dust off the Cape Verde Islands, dirtying everything on board. In 1844 Ehrenberg was surprised to find that the valves of freshwater diatoms comprised a substantial component of Darwins dust samples.Recent samples (e.g. those collected in 1982 aboard the French research vessel Le Chinon) demonstrate that about 50% these diatoms belong to planktonic taxa such as Aulacoseira.. The remainder are freshwater benthics. Where do they come from?

  • Saharan dust storm over adjacent Atlantic Ocean and ODP core siteimage: terra.nasa.govODP658CArrows indicatedominant winter wind direction

  • ODP658C core logdeMenocal et al., (2000) Quaternary Science Rev., 19, 347-361

  • Dust sources: dried beds of early-mid Holocene Saharan lakesRelict shorelines (in background), L. Asal, Djibouti (PAGES News)Yardangs in lake sediments, C. Sahara

  • Summer monsoon climates of N.Africa and the Near EastSE TradesSW Monsoon1000 mmMay 01- Sept 31

  • Four N. African palaeosites1. Sebhka Mellala 3. Oyo (West Nubia) 5. Fayum 2. Lake Chad 4. Lake Abh12354

  • Palaeo-lake deposits, Sebhka Mellala,Algeria8.2 cal kacold snap

  • Lake Chad:recent hydrological changeshttp://edcwww.cr.usgs.gov/earthshots/slow/LakeChad/LakeChad1963199750 km

  • Lake Mega-Chad

    1100 ft (300m)shoreline dates to~20-30 ka BP. L. Mega-Chad covered ~600 000 km2 and was ~200 m deepBougdoumaKajemarum

  • Palaeo-lake deposits, Bougdouma,Niger

  • Late Holocene climate change, Kajemarum Oasis, NE Nigeriafrom: Holmes et al., (1998) J. Paleolimnology, 20, 369-380deep freshshallow saline

  • West Nubian sites

  • West Nubianpalaeo-lakeHoelzmann et al. (2001) Palaeo3 169, 193-217.

  • Pollen evidencefrom: Roberts, N. (1996) The Holocene, 2 ed.

  • Lake Ahb, Ethiopia~4200cal yr BP

  • Variations in Nile dischargeThe Nilometer at Roda(A.D.641 - present)Said (1993) The River Nile: Geology, Hydrology and Utilization Pergamon Press

  • Nile flow (9000 - 300 BC)

  • Lake Moeris(Fayum depression)9 8 7 6 5 4 3 2 1 0 ka BP +25

    0

    -25

    -50Elevation (m, asl)Birket Qarun??

  • The end of the humid period and the demise of the Egyptian Old Kingdom(2180 BC;~4200 cal yr BP)Lo, the desert claims the landTowns are ravaged, Upper Egypt became a wastelandLo, everyone's hair [has fallen out]Lo, great and small say, "I wish I were dead"Lo, children of nobles are dashed against wallsInfants are put on high groundFood is lackingWearers of fine linen are beaten with [sticks]Ladies suffer like maidservantsLo, those who were entombed are cast on high groundsMen stir up strife unopposedGroaning is throughout the land, mingled with lamentsSee now the land deprived of kingshipWhat the pyramid hid is empty[The] People are diminished.(Egyptian sage, Ipuwer)

  • low dust influxS.W. Egypt** Malville et al., (1998), Nature 392, 488-491;** (discharge units are billion cumecs/yr) arid wet arid11 10 9 8 7 6 5 4 3 2 1 0 ka BP Oyo, SudanL. FayumL. Ahb,200 100high dust influxODP685CLake ChadS. Mellalahighdrylow inter.NubiaNile R.**

  • Vegetation of north and central Africa: 8000 ka BP

    pink = desert; pale yellow = grass savannahttp://www.uni-mannheim.de/phygeo/8000BP.htm

  • Rock art, Tassilli and Ennedi massifs, central and eastern Saharaa and c: http://ennedi.free.fr/bcaa= mouflon; b, c = giraffes

  • Sites in Arabia and PakistanYemen Oman Thar desert74KL

  • 74 KL: d18O, dust deposition and CaCo3 productionDust minimum 78508850

  • Holocene climate change in Arabia11 10 9 8 7 6 5 4 3 2 1 0 ka BP Rock hyrax (Procaviacapensis) middens agricultureArchaeological recordabandonedvillageshttp://www.usgs.gov/public/press/ public_affairs/press_releases/pr1482.htmlData from:wet hyperaridYEMEN OMANCalcite deposition rate in Hoti Cave(Neff et al., (2001) Nature, 411, 290-292.mm/yr1074 KLdust minimum

  • Indian subcontinent: Thar desert

  • Thar desert paleolake record

  • Changing palaeo-climates in southern Africa: the Mega-Kalahari

  • Dune-activity phases, southern Africafrom: OConnor and Thomas (1999)Quaternary Research, 52, 44-55.

  • Monsoon palaeoclimate sites, NW Australia121. Gregory Lakes2. Fitzroy R. basinNE Trades (Nov. -April)

  • Late Pleistocene pluvial phases in NW Australiafrom: Bowler et al., (2001) Quaternary International, 83-85, 63-80.

  • Post-glacial monsoon initiationfrom: Wrywoll and Miller (2001) Quaternary International, 83-85, 119-128.

  • Selected palaeoclimate sites, Atacama desert and neighbouring areas030S1231. Salar de Atacama, Chile2. Lake Titicaca, Bolivia3. Galapagos archipelagoMocheculture area

  • Late Quaternary wet phases, Salar de Atacamafrom: Bobst et al., (2001) Palaeo3, 173, 21-42.

  • Late Holocene climatic variation, Bolivian altiplanofrom: Abbot et al., (1997) Quaternary Research, 47, 169-180Moche culture

  • A 6000-yr record of El Nio activity from the Galapagos Islands

  • Millenial-scale variablity of El Nio events in the Galapagos IslandsData: Riedinger et al., (2002) J. Paleolimnology 27, 1-7.435 events in last 6000 yearsBainbridge Crater LakeDuring moderate El Nio events the surface waters of this hypersaline lake become relatively fresh and carbonates are precipitated; during severe events there is erosion of the crater walls into the lake. Laminae in the organic-rich salts that have collected on the lake bed record these events