late quaternary environments of the dry tropics and subtropics Ô north africa Ô arabia - india Ô...
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Late Quaternary environments of the dry tropics and subtropics
North Africa Arabia - India Australia South Africa South America
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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 Darwin’s 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?
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Saharan dust storm over adjacent Atlantic Ocean and
ODP core site
image: terra.nasa.gov
ODP658C
Arrows indicate
dominant winter wind
direction
HMS Beagle
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ODP658C core log
deMenocal et al., (2000) Quaternary Science Rev., 19, 347-361
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Dust sources:
dried beds of early-mid
Holocene Saharan
lakes
Relict shorelines (in background), L. Asal, Djibouti (PAGES News)
Yardangs in lake sediments, C. Sahara
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Summer monsoon climates of N.Africa and
the Near East
SE Trades SW Monsoon
<100 mm
>1000 mmMay 01- Sept 31
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Four N. African palaeosites1. Sebhka Mellala 3. Oyo (West Nubia) 5. Fayum2. Lake Chad 4. Lake Abhé
1
2
3
5
4
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Palaeo-lake
deposits, Sebhka Mellala,Algeria
8.2 cal kacold snap
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Lake Chad:recent
hydrological changes
http://edcwww.cr.usgs.gov/earthshots/slow/LakeChad/LakeChad
1963
1997
50 km
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Lake Mega-Chad
1100 ft (300m)shoreline dates to
~20-30 ka BP. L. Mega-Chad
covered ~600 000 km2
and was ~200 m deep
Bougdouma
Kajemarum
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Palaeo-lake
deposits, Bougdoum
a,Niger
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Late Holocene climate change,
Kajemarum Oasis, NE Nigeria
from: Holmes et al., (1998) J. Paleolimnology, 20, 369-380
deep fresh
shallow saline
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West Nubian sites
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West Nubianpalaeo-
lake
Hoelzmann et al. (2001) Palaeo3 169, 193-217.
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Pollen evidence
from: Roberts, N. (1996) “The Holocene”, 2° ed.
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Lake Ahbé,
Ethiopia
~4200cal yr BP
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Variations in Nile
discharge
The Nilometer at Roda(A.D.641 - present)
Said (1993) “The River Nile: Geology, Hydrology and Utilization” Pergamon Press
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Nile flow (9000 - 300 BC)
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Lake Moeris
(Fayum depression
)
9 8 7 6 5 4 3 2 1 0 ka BP
+25
0
-25
-50Ele
vati
on
(m
, asl
)
Birke
t Qaru
n
??
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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)
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S.W. Egypt*
* Malville et al., (1998), Nature 392, 488-491;** (discharge units are billion cumecs/yr)
arid wet arid
11 10 9 8 7 6 5 4 3 2 1 0 ka BP
Oyo, Sudan
L. Fayum
L. Ahbé,
≥200 ≤100
low dust influx high dust influx ODP685C
Lake Chad
S. Mellalahigh drylow inter.
Nubia
Nile R.**
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Vegetation of north
and central Africa:
8000 ka BP
pink = desert; pale
yellow = grass
savanna
http
://ww
w.u
ni-m
annheim
.de/p
hygeo/8
00
0B
P.h
tm
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Rock art, Tassilli and Ennedi
massifs, central and eastern
Sahara
a and c: http://ennedi.free.fr/
b c
a
a= mouflon; b, c = giraffes
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Sites in Arabia and Pakistan
Yemen Oman Thar desert
74KL
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74 KL: 18O, dust deposition and CaCo3
production
Dust minimum
78508850
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Holocene climate change in Arabia
11 10 9 8 7 6 5 4 3 2 1 0 ka BP
Rock hyrax (Procaviacapensis) middens
agriculture
Archaeological record
abandonedvillages
http://www.usgs.gov/public/press/public_affairs/press_releases/pr1482.html
Data from:
increasing aridity and/or overgrazing
5.2 2.5
wet hyperarid
YEM
EN
O
MA
N Calcite deposition rate in Hoti Cave(Neff et al., (2001) Nature, 411, 290-292. mm/yr
1
0
74 KL dust minimum
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Indian subcontinent: Thar desert
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Thar desert paleolake
record
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Changing palaeo-climates
in southern Africa:
the Mega-
Kalahari
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Dune-activity phases, southern
Africa from: O’Connor and Thomas (1999)Quaternary Research, 52, 44-55.
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Monsoon palaeoclimate
sites, NW Australia 1
2
1. Gregory Lakes2. Fitzroy R. basin
NE Trades (Nov. -April)
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Late Pleistocene pluvial phases in
NW Australia
from: Bowler et al., (2001) Quaternary International, 83-85, 63-80.
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Post-glacial
monsoon
initiation
from: Wrywoll and Miller (2001) Quaternary International, 83-85, 119-128.
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Selected palaeoclimate
sites, Atacama
desert and neighbouring
areas
0°
30°S
1
2
3
1. Salar de Atacama, Chile2. Lake Titicaca, Bolivia3. Galapagos archipelago
Mocheculture area
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Late
Quate
rnary
wet
phase
s, S
ala
r de
Ata
cam
a
from: Bobst et al., (2001) Palaeo3, 173, 21-42.
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Late Holocene climatic variation, Bolivian
altiplano
from: Abbot et al., (1997) Quaternary Research, 47, 169-180
Moche culture
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A 6000-yr record of El Niño activity from the Galapagos
Islands
Bainbridge Crater Lake
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Millenial-scale variablity of El Niño events in the Galapagos
Islands
Data: Riedinger et al., (2002) J. Paleolimnology 27, 1-7.
435 events in last
6000 years
Bainbridge Crater LakeDuring moderate El Niño 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