Late Quaternary environments of the dry tropics and subtropics Ô North Africa Ô Arabia - India Ô...

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 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?

Saharan dust storm over adjacent Atlantic Ocean and

ODP core site

image: terra.nasa.gov

ODP658C

Arrows indicate

dominant winter wind

direction

HMS Beagle

ODP658C core log

deMenocal et al., (2000) Quaternary Science Rev., 19, 347-361

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

Summer monsoon climates of N.Africa and

the Near East

SE Trades SW Monsoon

<100 mm

>1000 mmMay 01- Sept 31

Four N. African palaeosites1. Sebhka Mellala 3. Oyo (West Nubia) 5. Fayum2. Lake Chad 4. Lake Abhé

1

2

3

5

4

Palaeo-lake

deposits, Sebhka Mellala,Algeria

8.2 cal kacold snap

Lake Chad:recent

hydrological changes

http://edcwww.cr.usgs.gov/earthshots/slow/LakeChad/LakeChad

1963

1997

50 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 deep

Bougdouma

Kajemarum

Palaeo-lake

deposits, Bougdoum

a,Niger

Late Holocene climate change,

Kajemarum Oasis, NE Nigeria

from: Holmes et al., (1998) J. Paleolimnology, 20, 369-380

deep fresh

shallow saline

West Nubian sites

West Nubianpalaeo-

lake

Hoelzmann et al. (2001) Palaeo3 169, 193-217.

Pollen evidence

from: Roberts, N. (1996) “The Holocene”, 2° ed.

Lake Ahbé,

Ethiopia

~4200cal yr BP

Variations in Nile

discharge

The 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

-50Ele

vati

on

(m

, asl

)

Birke

t Qaru

n

??

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)

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.**

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

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

Sites in Arabia and Pakistan

Yemen Oman Thar desert

74KL

74 KL: 18O, dust deposition and CaCo3

production

Dust minimum

78508850

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

Indian subcontinent: Thar desert

Thar desert paleolake

record

Changing palaeo-climates

in southern Africa:

the Mega-

Kalahari

Dune-activity phases, southern

Africa from: O’Connor and Thomas (1999)Quaternary Research, 52, 44-55.

Monsoon palaeoclimate

sites, NW Australia 1

2

1. Gregory Lakes2. Fitzroy R. basin

NE Trades (Nov. -April)

Late Pleistocene pluvial phases in

NW Australia

from: Bowler et al., (2001) Quaternary International, 83-85, 63-80.

Post-glacial

monsoon

initiation

from: Wrywoll and Miller (2001) Quaternary International, 83-85, 119-128.

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

Late

Quate

rnary

wet

phase

s, S

ala

r de

Ata

cam

a

from: Bobst et al., (2001) Palaeo3, 173, 21-42.

Late Holocene climatic variation, Bolivian

altiplano

from: Abbot et al., (1997) Quaternary Research, 47, 169-180

Moche culture

A 6000-yr record of El Niño activity from the Galapagos

Islands

Bainbridge Crater Lake

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