Southern the

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P R O C E E D I N G S O F A N I N T E R N A T I O N A L S Y M P O S I U M H E L D B Y T H E S O U T H A F R I C A N S O C I E T Y F O R Q U A T E R N A R Y R E S E A R C H / S W A Z I L A N D /

29 A U G U S T - 2 S E P T E M B E R 1983 ff f > ? X / * ^ K 3

Late Cainozoic

Palaeoclimates of the Southern Hemisphere

Edited by

J.C.VOGEL

CSIR, Pretoria, South Africa With the assistance of:

N I C O L I N E B A S S O N / U R S U L A V O G E L / A N N E M A R I E F U L S

O F F P R I N T

A. A.B A L K E M A / R O T T E R D A M / BOSTON

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Late Cainozoic palaeoclimates of the Southern Hemisphere

Proceedings of an international symposium held by the South African Society for Quaternary Research in Swaziland, 29 August-2 September 1983

edited by J . C . V O G E L

CSIR, Pretoria, South Africa With the assistance of

N I C O L I N E B A S S O N , U R S U L A V O G E L & A N N E M A R I E F U L S 1984, 25 x 18 cm, 536 pp., 9 photos

Cloth, H f l . H 0 / $40.00 / £ 2 5 . 5 0 Publication date: 26 October 1984

In order to be able to reconstruct what climatic changes took place in the past, knowledge o f the palaeoclimates o f the Southern Hemisphere is of the utmost importance. The Antarctica and the surrounding oceans play the major role in regulating atmospheric circulation patterns; even across the equator. In addition, evidence from deep sea cores has recently indicated that climatic change in the south actually preceded that in the northern regions by some 3000 years.

C O N T E N T S

Palaeoclimatology. Climatic evolution in the Southern Hemisphere and the equatorial region during the Late Cenozoic ( H . F l o h n , Univ.

B o n n ) ; A climatic model o f the Last Glacial/Interglacial transition based on palaeotemperature and palaeohydrological evidence (S.P.

Harrison, S.E.Metcalfe & F.A.Street-Perrott, School Geogr., O x f o r d , A . B . Pittock, C S I R O , Mordialloc, Australia, C.N.Roberts, Lough- borough Univ. Technol. & M.J.Salinger, Univ.East Anglia, U K ) ; etc.

South America. Late Cainozoic glacial variations in South America south of the equator (J.H.Mercer, O h i o State Univ., Columbus, U S A ) ; Late Quaternary climates of Chile (C.J.Heusser, New Y o r k Univ.);

Late Glacial glaciation and the development of climate in southern South America (W.Lauer & P.Frankenberg, Univ. B o n n ) ; etc.

Australasia. New Zealand climate: The last 5 million years ( M . J . Salinger, N Z Meteorol. Service, Wellington); Glacial age environments of inland Australia (J.M.Bowler, Australian Natl. Univ., Canberra & R.J.Wasson, C S I R O , Canberra): Evolution of Australian landscapes and the physical environment of aboriginal man (J.B.

F i r m a n , Geological Survey, Parkside, S.Australia); etc.

Southern Africa. Late Quaternary environments in S.Africa ( K . W . Butzer, Univ. Texas, A u s t i n ) ; The evidence from northern Botswana of Late Quaternary climatic change (H.J.Cooke, Univ., Botswana, Gaborone); Investigations on archaeological charcoals from Swazi- land, using S E M techniques (J.Prior, Imperial College, L o n d o n ) ; etc.

The Southern deserts. Ancient ergs of the Southern Hemisphere (D.S.G.Thomas & A . S . G o u d i e , Univ. O x f o r d , U K ) ; Late Quaternary palaeoenvironments in the desert dunefields of Australia (R.J.Wasson);

A r i d i t y in southern A f r i c a : Age, origins and expression in landforms and sediments (N.Lancaster, Univ.Cape T o w n ) ; etc.

African faunal record. Horses, elephants and pigs as clues in the African later Cainozoic (H.B.S.Cooke, Dalhousie Univ., Halifax, Canada); The Terminal Miocene Event: A critical environmental and evolutionary episode? ( C . K . B r a i n , Transvaal Museum, Pretoria); etc.

FROM THE SAME PUBLISHER

I S S N 0168-6151 Modern Quaternary research in southeast Asia

(Bartstra,G.-J. & W . A . Casparie, eds.)

1975-, 23 c m , each c.120 pp., Hfl.45 / $18.50 / £10.50 A n n u a l publication. Information on research projects &

results. Bibliographies, plates, maps, figs.

Cresswell, M . M . & P. Vella (eds.) 90 6191088 9 Gondwana five - Selected papers and abstracts ofpapers presented at the fifth international Gondwana symposium,

Wellington, New Zealand, 11-16 February 1980 1981,25 cm, 352 pp., H f l . 120 / $ 4 8 . 0 0 / £ 2 8 The supercontinent which some 180 million years ago consisted of South America & Africa as 'western*

Gondwanaland and o f India, Australia & Antarctica as 'eastern' Gondwanaland. Paleontology & stratigraphy;

Structure & paleogeology; Break-up of Gondwanaland.

D i n e l e , R . V . , W . G . Siesser & A R . N e w t o n

90 6191099 4 Mesozoic and Tertian geologv of southern Africa 1983,28 cm, 385 pp., HÍ1.105 / $39.50 / £24.50

The first book on the latest phase o f S. Africa's structural, sedimentological and igneous development. Based on recently amassed data. Triassic to early Jurassic rocks o f the intracratonic basins; Cape F o l d Belt; M i d d l e Jurassic to Lower Cretaceous; Upper Cretaceous; Tertiary; Mesozoic &

Tertiary igneous activity; References; Indexes.

Ehlers. J ü r g e n (editor) 90 6191 233 7 Glacial deposits in North-West Europe

1983,28 cm, 512 pp., Hfl.dS / $48.50 / £29

Intended as a textbook for students & informed amateurs. &

as a guide for professional geoscientists. The 53 chapters covering Norway, Sweden, Denmark, Germany & the Netherlands, are richly illustrated by 409 b / w photos and 95 c o l o r photos. Topics covered are; drift prospecting, modern varve chronology, fine gravel analysis, internal structure o f thrust moraines, stratigraphical interpretation of well-logs, echo-sounding o f N o r t h Sea deposits, erratic pebbles as indicators, till fabrics, palaeontology o f glacial deposits, multi-component till analyses, glacial deposition on the continental shelf and the genetic interpretation of glacial landforms. The regional stratigraphy & glacial chronology of each of the 5 countries is reviewed. The bibliography contains 700 entries. Detailed index.

I S S N 0168-6208 Palaeoecologv of Africa - and the surrounding islands ( J . A . Coetzee & E . M . van Zinderen Bakker, eds.) 1966-, 22 cm, c.250 pp., Hfl.75 / $27.50 / £17.50 A n n u a l publication. Comprehensive & up-to-date information on research in many different disciplines which give an overall insight into the environmental history o f Africa.

Volumes 1,2,3 and 5 are out of print.

Anderson, J o h n M . & Heidi M . A n d e r s o n 90 6191 282 2 Palaeoflora of southern Africa: Molteno Formation (Triassic) A series of six volumes on the Molteno Formation which will cover the microflora as well as the diverse insect fauna. The study is based on a collection of 14,000 catalogued slabs from 44 localities. Throughout, taxonomic & phytogeographic considerations involve the full G o n d w a n a realm, which makes the publication o f interest to palaeontologists from all pans of the world.

All books available from your bookseller or directly from the publisher:

A.A.Balkema, P.O.Box 1675, NL-3000 BR Rotterdam, Netherlands A.A.Balkema, P.O.Box 230, Accord, MA 02018, USA

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SASQUA international Symposium /Swaziland/29 August - 2 September 1983

Radiocarbon dating of speleothems from the Rössing cave, Namib desert, and palaeoclimatic implications

K L A U S H E I N E

Universität Regensburg, Germany M E B U S A . G E Y H

Niedersächsisches Landesamt für Bodenforschung, Hannover, Germany

ABSTRACT. A b o u t 2 km w e s t o f t h e Rössingberge i n t h e Namib d e s e r t a t a b o u t 340 m a b o v e s e a l e v e l , a s m a l l c a v e s y s t e m w i t h s t a l a c t i t e s , s t a l a g m i t e s , f l o w s t o n e , p o p c o r n a n d o t h e r s i n t e r f o r m a t i o n s was i n v e s - t i g a t e d i n 1978 a n d 1 9 8 1 . S p e l e o t h e m s have b e e n f o r m e d s i n c e t h e T e r - t i a r y . A s t h e c a v e i s w i t h i n a s m a l l c a t c h m e n t a r e a , t h e s p e l e o t h e m s r e f l e c t c h a n g i n g p a l a e o h y d r o l o g i c a l a n d p a l a e o c l i m a t o l o g i c a l c o n d i t i o n s i n t h e Namib d e s e r t i n t h e v i c i n i t y o f t h e c a v e r a t h e r t h a n t h o s e o f t h e e s c a r p m e n t i n t h e e a s t .

> A c c o r d i n g t o t h e C14 d a t e s , t h e c l i m a t e a f t e r 41 500 BP c a n be d i v i d - e d i n t o f i v e p h a s e s . U n t i l a b o u t 25 500 BP r a t h e r h u m i d c o n d i t i o n s p r e v a i l e d a s c a v e s i n t e r was f o r m e d . A f t e r w a r d s t h e c l i m a t e r e m a i n e d d r y i n t h e s t u d y a r e a . As f r o m 19 000 BP, t h e i n t e r i o r o f S o u t h West A f r i c a a l s o became a r i d .

INTRODUCTION

Some q u e s t i o n s o f t h e L a t e Q u a t e r n a r y c l i m a t i c e v o l u t i o n i n t h e Namib d e s e r t w i l l be d i s c u s s e d b r i e f l y . D u r i n g r e c e n t y e a r s many s c i e n t i s t s h a v e t r i e d t o f i n d e v i d e n c e f o r o r a g a i n s t t h e p e n e t r a t i o n o f h y p o t h e r - m a l ( G l a c i a l Maximum) w i n t e r r a i n f a l l i n t h e Namib. A c c o r d i n g t o R u s t and S c h m i d t ( 1 9 8 1 ) , f o r e x a m p l e , w i n t e r r a i n f a l l p e n e t r a t e d a s f a r n o r t h a s 20 ° S d u r i n g t h e l a s t p l e n i g l a c i a l . V a n Z i n d e r e n B a k k e r

( 1 9 8 3 a , b ) , on t h e o t h e r h a n d , a r g u e d t h a t w i n t e r r a i n f a l l n e v e r e x t e n d e d so f a r n o r t h d u r i n g t h e L a t e Q u a t e r n a r y . H i s p o l l e n s t u d y i n d i c a t e s t h a t t h e c l i m a t i c c o n d i t i o n s a t S o s s u s v l e i h a d n o t c h a n g e d s i n c e a t l e a s t 18 0 0 0 BP. V o g e l ( 1 9 8 2 ) c o n c l u d e d f r o m d a t e s o b t a i n e d by h i m on s i l t , c a l c r e t e s , a n d one wood s a m p l e t a k e n a t Homeb on t h e K u i s e b R i v e r , t h a t t h e l a s t h u m i d p e r i o d i n t h e Namib d e s e r t e n d e d a b o u t 28 000 BP.

A b o u t 2 km w e s t o f t h e Rössingberge ( 1 4 ° 4 8^f E, 2 2 ° 3 1 , 5^? S ) a t 338 m a b o v e s e a l e v e l , a s m a l l c a v e w i t h a v a r i e t y o f s p e l e o t h e m s r e f l e c t s t h e c l i m a t i c e v o l u t i o n i n t h e v i c i n i t y o f t h e Rössingberge i n t h e c e n t r a l Namib d e s e r t . Two Th230/U234 d a t e s o f s p e l e o t h e m s e x c e e d i n g 300 000 y r s u p p o r t t h e g e o m o r p h i c e v i d e n c e t h a t t h e c a v e a n d t h e o l d e s t s i n t e r f o r m a t i o n m i g h t be o f T e r t i a r y o r i g i n . I n t h i s p a p e r a t t e n t i o n i s f o c u s e d on t h e L a t e Q u a t e r n a r y o n l y .

S p e l e o t h e m s f r o m a r i d z o n e s c a n be c o n s i d e r e d a s " c l o s e d s y s t e m s "

w i t h r e s p e c t t o c a r b o n i s o t o p e s . T h e r e f o r e , s u c h s a m p l e s a r e most

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s u i t a b l e f o r C14 d a t i n g . The c a l i b r a t i o n u n c e r t a i n t y o f t h e d a t e I s a b o u t ± 1000 y e a r s . I n s p i t e o f t h i s C14 a g e s seem t o be more r e l i a b l e t h a n t h o s e o f any o t h e r s a m p l e s f r o m t h e Namib d e s e r t , s u c h a s c a l - c r e t e s o r f l u v i a l : l i e s e d i m e n t s w h i c h a r e o f t e n c h a n g e d d i a g e n e t i c a l l y .

THE CAVE AND PERIODS OF SPELEOTHEM FORMATION

The c a v e i s s i t u a t e d i n a n a r r o w b e l t o f c a l c a r e o u s r o c k s t h a t emerges a f e w m e t r e s a b o v e t h e o l d Namib d e s e r t s u r f a c e w i t h i n a n a t u r a l c a t c h - nient a r e a o f a f e w km ( F i g . 1 ) . T h u s , t h e g r o w t h o f s p e l e o t h e m s was d e t e r m i n e d by t h e l o c a l p r e c i p i t a t i o n i n t h e v i c i n i t y o f t h e c a v e o n t h e w e s t e r n s l o p e s o f t h e Rössingberge r a t h e r t h a n by t h a t f r o m t h e e s c a r p m e n t i n t h e e a s t .

The c a v e c o n s i s t s o f t h r e e chambers s i t u a t e d p a r a l l e l t o t h e NNW/SSE d i r e c t i o n o f t h e f o l d e d r o c k s i n t h e Namib. The chambers a r e a b o u t 10-20 m b e n e a t h t h e s u r f a c e . T h e i r w i d t h s r a n g e f r o m a f e w m e t r e s t o a b o u t 15 m, t h e i r l e n g t h s f r o m a b o u t 10-25 m. The h e i g h t o f t h e cham-»

b e r s c h a n g e s f r o m s e v e r a l d e c i m e t r e s t o c. 3 m.

H°45'E

K.Heine 1983

Reference, Main Map

Dry River Bed ^Z*S>Z^ Contour Line

=—=—=— Railways = Roads

F i g u r e 1. Map o f t h e s t u d y a r e a .

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A c c o r d i n g t o t h e g e o m o r p h o l o g i c s i t u a t i o n t h e c a v e was f o r m e d by l i m e s o l u t i o n o r e r o s i o n d u r i n g p r e - P l e i s t o c e n e t i m e s . O n l y a f e w p o i n t s i n t h e c a v e d i s p l a y c a v e d e p o s i t s as s t a l a c t i t e s , s t a l a g m i t e s , f l o w s t o n e , and p o p c o r n . A t p r e s e n t , t h e c a v e a p p e a r s t o be c o m p l e t e l y d r y t h o u g h d r o p s o f s e e p i n g w a t e r have been o b s e r v e d d u r i n g e x t r e m e l y wet y e a r s .

I n t h e n o r t h e r n p a r t o f t h e c a v e , a huge s t a l a g m i t e ( F i g . 2) s t a n d s b e n e a t h a b i g f i s s u r e w h i c h a l l o w e d f i n e a e o l i a n s a n d s f r o m t h e Namib d e s e r t t o e n t e r t h e c a v e t o g e t h e r w i t h t h e d r i p p i n g w a t e r . They a r e f o u n d i n b e t w e e n t h e y o u n g e s t f l o w s t o n e l a y e r s ( F i g . 2) s u r r o u n d i n g t h e e a s t e r n a n d s o u t h e r n f l a n k s o f t h e s t a l a g m i t e .

Rössing Cave, Namib Desert

F i g u r e 2. S p e l e o t h e m m o r p h o l o g y a n d s a m p l i n g p o i n t s f o r i s o t o p e a n a l y - s e s i n t h e Rössing c a v e .

The c o n v e n t i o n a l C14 a g e s o f t h e u p p e r m o s t f l o w s t o n e l a y e r s ( F i g . 2 ) r a n g e f r o m 37 000 - 26 800 BP. The s p e l e o t h e m s , f o r m e d u n t i l a b o u t 35 000 B P , c o n s i s t o f m a s s i v e c a l c i t e d e p o s i t s . L a t e r o n , s a n d h o r i - z o n s a r e i n t e r c a l a t e d . The c o n v e n t i o n a l C14 d a t e s o f s p e l e o t h e m s a m p l e s f r o m o t h e r p l a c e s i n t h e c a v e ( T a b l e 1) a l s o show t h a t s i n t e r f o r m a t i o n s t e r m i n a t e d a t 26 500 BP. T h i s h o l d s t r u e a l s o f o r t h e pop- c o r n d e p o s i t s c o n s i s t i n g o f i r r e g u l a r l y a l t e r n a t i n g l i g h t a n d d a r k l a y e r s o f a r a g o n i t e a n d c a l c i t e . T h e i r f o r m a t i o n b e g a n b e f o r e 41 000 BP. The o u t e r p a r t o f a u n i q u e s t a l a c t i t e c u r t a i n y i e l d e d a d a t e o f 37 000 BP.

O n l y c o n v e n t i o n a l C14 d a t e s h a v e b e e n d i s c u s s e d up t o now. I t h a s b e e n known, h o w e v e r , s i n c e t h e method f o r C14 d a t i n g o f s p e l e o t h e m s was i n t r o d u c e d by F r a n k e ( 1 9 5 1 ) a n d p r o v e d t o be a p p l i c a b l e ( F r a n k e e t a l . 1 9 5 8 ) , t h a t a " r e s e r v o i r c o r r e c t i o n " o f a t l e a s t -1000 y e a r s i s n e c e s - s a r y t o o b t a i n a c t u a l a g e s . L a b e y r i e e t a l . ( 1 9 6 7 ) e v e n f o u n d a c o r - r e c t i o n v a l u e o f up t o -3500 y e a r s f o r u n c o v e r e d a r e a s . H o w e v e r , as we do n o t know t h e g e o e c o l o g i c , p e d o l o g i c a n d s e d i m e n t o l o g i c s i t u a t i o n i n t h e Namib d e s e r t a r o u n d 30 000 BP, we a c c e p t V o g e l ' s ( 1 9 8 2 ) c o r r e c t i o n v a l u e o f -1000 y e a r s f o r o u r g e o c h r o n o l o g i c a l e v a l u a t i o n . T h i s does n o t e x c l u d e t h a t t h e r e s u l t i n g t i m e s c a l e may have t o be s h i f t e d f u r - t h e r on by up t o -2500 y e a r s . I n t h i s c a s e , t h e e n d o f s p e l e o t h e m

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f o r m a t i o n m i g h t have c o i n c i d e d w i t h t h e d a t e of 23 000 BP o b t a i n e d f r o m wood f o u n d i.n s i l t s a t Homeb ( V o g e l 1 9 8 2 ) .

T a b l e I . C o n v e n t i o n a l C14 a g e s , C14 c o n t e n t (pmc) and 6C13 v a l u e s ( %o ) f r o m s p e l e o t h e m s o f t h e "Rössing c a v e In t h e Namib d e s e r t .

Kv K00 s u b s t a n c e RC age RC c o n t e n t 6C13

( y e a r s BP) (pmc) (%o)

11634 610 s t a l a g m i t e 26 630 ± 500 3.6 ± 0.2 -5.4

11635 613 f l o w s t o n e 26 780 ⁺ 360 3.6 ± 0.2 -7.9

11636 612 f l o w s t o n e 29 830 ^± 660 2.4 ± 0.2 -3.6

11637 616 f l o w s t o n e 33 590 ^± 1200 1.4 ± 0.2 -4.0

11638 619 f l o w s t o n e 36 950 ^± 1040 1.0 ± 0.1 -5.0

11639 621 s t a l a c t i t e c u r t a i n 37 000 ^± 1700 1.0 ± 0.2 -6.8

11640 622 c a v e p o p c o r n 41 500 ^± 1280 0.6 ± 0.1 -5.3

9909 162 c a v e p o p c o r n 29 700 ^± 1360 2.5 ± 0.4 -4.5

9910 162a c a v e p o p c o r n 26 700 ^± 540 3.6 ± 0.2 -5.7

9489 1 6 2 ( 1 ) c a v e p o p c o r n 26 530 ^± 920 3.7 ± 0.4 -2.0

PALAEOCLIMATIC IMPLICATIONS

Our r e s u l t s of r a d i o m e t r i c d a t i n g s t o g e t h e r w i t h s e d i m e n t o l o g i c o b s e r - v a t i o n s a t t h e s a m p l i n g s i t e s i n t h e Rössing c a v e y i e l d a r a t h e r d i f f e - r e n t i a t e d p i c t u r e of t h e L a t e Q u a t e r n a r y e v o l u t i o n of t h e c l i m a t e i n the Namib d e s e r t ( H e i n e 1 9 8 2 ) . V a r i o u s p h a s e s c a n be d i s t i n g u i s h e d f o r t h e M i d d l e W e i c h s e l i a n p l u v i a l and o t h e r p h a s e s o c c u r r i n g up t o t h e p r e s e n t . Once d a t e s of t h e t i m e b e f o r e 41 000 BP become a v a i l a b l e , i t w i l l be p o s s i b l e t o e l o n g a t e t h e s e q u e n c e by c o u n t i n g p h a s e s b a c k w a r d s :

PHASE 5: 40 000-34 000 BP

A t t h e end of t h i s p h a s e , t h e L a s t W e i c h s e l i a n p l u v i a l w i t h c o m p a c t s i n t e r f o r m a t i o n t e r m i n a t e d w i t h i n t h e Namib d e s e r t . M i s s i n g s a n d I n c l u s i o n s i n d i c a t e t h a t a c l o s e d p l a n t c o v e r m i g h t h a v e e x i s t e d . I n v i e w o f t h e p o p c o r n f o r m a t i o n , t h e h u m i d i t y must have been h i g h e r t h a n l a t e r on. V a r i o u s w a l l c o a t i n g s may d a t e b a c k , h o w e v e r , t o t h e E a r l y Q u a t e r n a r y o r e v e n t o t h e T e r t i a r y .

PHASE 4: 34 000-27 000 BP

T h i s p h a s e i s t h e b e g i n n i n g o f t h e a r i d i f i c a t i o n i n t h e c e n t r a l Namib.

At l e a s t t h r e e n o t i c e a b l e c l i m a t i c f l u c t u a t i o n s o c c u r r e d d u r i n g w h i c h more humid c o n d i t i o n s w e r e r e p l a c e d by more a r i d ones and v i c e v e r s a . T h i s i s i n d i c a t e d by i n t e r c a l a t i n g s a n d l a y e r s w h i c h a c c o u n t f o r a more w i n d y c l i m a t e and p r o b a b l y n o t c o m p l e t e l y c l o s e d p l a n t c o v e r . H o w e v e r ,

i t was s t i l l humid enough f o r f o r m a t i o n of compact s i n t e r . T h i s p h a s e c o i n c i d e d w i t h the c a l c r e t e f o r m a t i o n on t h e 40 m t e r r a c e a l o n g t h e K u i s e b R i v e r ( V o g e l 1982) w h i c h l a s t e d f r o m 33 000 t o 28 000 BP.

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PHASE 3: c . 27 000-25 500 BP

Humid c o n d i t i o n s p r e d o m i n a t e d once more and compact s i n t e r w i t h o u t a e o - l i a n s a n d i n c l u s i o n s was f o r m e d . I t i s n o t known w h e t h e r t h i s was due t o d e c r e a s i n g w i n d a c t i v i t y o r once more t o a c o m p l e t e l y c l o s e d p l a n t c o v e r i n t h e Namib d e s e r t . The h u m i d i t y d r o p p e d d r a s t i c a l l y a t t h e end as p o p c o r n f o r m a t i o n e n d e d . P h a s e 3 a n d 4 may be i d e n t i c a l . D u r i n g t h i s p h a s e t h e r a i n f a l l i n t e n s i t y i n t h e i n t e r i o r i n c r e a s e d a n d p e b b l e d e p o s i t s f r o m t h e 40 m t e r r a c e o f t h e K u i s e b R i v e r were removed ( V o g e l 1 9 8 2 ) .

PHASE 2: 25 000-19 000 BP

F r o m t h i s t i m e onwards t h e Namib d e s e r t r e m a i n e d d r y . No f u r t h e r s i n t e r f o r m a t i o n o c c u r r e d i n t h e Rössing c a v e . However, a c c o r d i n g t o H e i n e ( 1 9 8 2 ) t h e i n t e r i o r o f SW A f r i c a was more humid t h a n i t was a f t e r 19 000 BP. I n t h e K u i s e b v a l l e y , dunes s t a r t e d t o b l o c k t h e r i v e r bed and v l e i s i l t was d e p o s i t e d . A t t h e end o f t h i s p h a s e t h e a r i d i f i c a - t i o n o f t h e Namib d e s e r t was c o m p l e t e ( V a n Z i n d e r e n B a k k e r 1983a, b ) .

PHASE 1: a f t e r 19 000 BP

| A c c o r d i n g t o o u r own d a t a f r o m t h e Rössing c a v e as w e l l as t h e r e s u l t s o f o t h e r p u b l i c a t i o n s m e n t i o n e d a l r e a d y , m a j o r c l i m a t i c f l u c t u a t i o n s no l o n g e r o c c u r r e d . The Namib d e s e r t and t h e e a s t e r n e s c a r p m e n t r e m a i n e d u n d e r a r i d c o n d i t i o n s c o n t r a r y t o t h e a s s u m p t i o n by R u s t and S c h m i d t ( 1 9 8 1 ) t h a t t h e a r e a b e t w e e n 22 a n d 23 ° S h a d b e e n humid d u r i n g t h e l a s t P l e n i g l a c i a l .

One o f t h e most i m p o r t a n t f i n d i n g s o f o u r s t u d y i s t h a t one h a s t o be c a r e f u l n o t t o t r a n s p o s e c h r o n o s t r a t i g r a p h i c s e q u e n c e s f r o m one a r e a t o a n o t h e r as d i f f e r e n t p a l a e o c l i m a t i c e v e n t s m i g h t h a v e been r e s p o n s - i b l e . T h e r e f o r e , c o r r e l a t i o n s b e t w e e n , f o r i n s t a n c e , d i f f e r e n t S o u t h A f r i c a n s t r a t i g r a p h i e s a n d t h e i r c o m p a r i s o n w i t h t h e m a r i n e o x y g e n i s o - t o p e r e c o r d c a n o n l y make s e n s e i f a t l e a s t t h e p a l a e o g e o g r a p h i c a l s i t u a t i o n s a r e t a k e n i n t o a c c o u n t . H e n c e , o u r c h r o n o l o g y o f t h e c l i m a - t i c e v o l u t i o n w i t h i n t h e Namib d e s e r t c a n be o f r e g i o n a l i f t i p o r t a n c e o n l y . Owing t o t h e l o n g h i s t o r y o f t h e Rössing c a v e s i n c e t h e T e r - t i a r y , t h i s c a v e w i t h i t s s p e l e o t h e m s seems t o be one o f t h e most s u i t - a b l e p l a c e s f o r r e c o n s t r u c t i n g t h e p a l a e o c l i m a t i c e v o l u t i o n o f t h e Namib d e s e r t n e a r 2 2 ° 3 0fS .

ACKNOWLEDGEMENTS

We t h a n k Dr GJ H e n n i g , I n s t i t u t für K e r n c h e m i e , Universität Köln, f o r t h e U/Th a g e d e t e r m i n a t i o n s o f two s t a l a g m i t e s a m p l e s a n d t h e D e u t s c h e F o r s c h u n g s g e m e i n s c h a f t f o r f i n a n c i a l s u p p o r t .

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