in the

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Eiszeitalter und Gegenwart Band 19 Seite 203-208 Öbringen/Württ., 31. Oktober 1968

Quaternary climatic changes in t h e Caribbean

and N. South-America

B y J . I . S . Z O N N E V E L D , U t r e c h t

S u m m a r y . This paper gives an inventarization o f the available data concerning quater nary climatic changes in the Caribbean and the northern parts o f South America.

It appears that in Colombia, N . W. Venezuela, the Leeward Islands o f the Netherlands Antilles and Barbados the pluvial periods coincided with the glacial periods in higher latitudes. The evidence for G u y a n a and Surinam is still insufficient to establish definitely the climatic evolution, altough the available data seem t o indicate that during the glacial periods the climate was less humid than at present: this would correspond with a shifting o f the "arid" belt over some 10 degrees.

Z u s a m m e n f a s s u n g . Es wurden in dieser kurzen Arbeit Literaturangaben über die quartären Klimaänderungen gesammelt, die aus dem karibischen Gebiet und den benachbarten Teilen Südamerikas bekannt sind. Man kann feststellen, daß in Kolumbien, Nordwest-Venezuela, Aruba, Curacao, Bonaire und Barbados pluviale Perioden etwa synchron waren mit den Glazialen in Gebieten höherer Breite.

Die Daten aus Guyana und Suriname lassen zwar noch keine endgültigen Schlüsse zu, doch deutet vieles darauf hin, d a ß dort während d e r Glazialzeiten trockenere klimatische Bedingungen herrschten als heute. D a s würde einer Verschiebung der „ariden" Zone um etwa 1 0 ° entsprechen. R e c e n t p a l a e o c l i m a t i c research in A f r i c a h a s i n d i c a t e d t h a t o n l y p a r t o f t h e p l u v i a l s t h a t w e r e r e c o g n i z e d i n different r e g i o n s o f t h e c o n t i n e n t , w e r e s y n c h r o n o u s w i t h t h e g l a c i a l p e r i o d s o f m o r e p o l e w a r d r e g i o n s ( c f . T R I C A R T , M I C H E L a n d V O G T , 1 9 5 7 ;

B E R N A R D , 1 9 6 2 ; B Ü D E L , 1 9 6 3 ; F A I R B R I D G E , 1 9 6 4 ; see a l s o P E N C K , 1 9 1 3 ) .

A s a g e n e r a l rule i t a p p e a r s t h a t d u r i n g t h e g l a c i a l p e r i o d s , t h e b o u n d a r i e s o f t h e different c l i m a t i c b e l t s shifted t o w a r d s t h e e q u a t o r . I n these periods t h e m e s o t h e r m a l z o n e s as w e l l as t h e a r i d z o n e s o f the n o r t h e r n h e m i s p h e r e w i l l h a v e m o v e d s o u t h w a r d a n d t h e b e l t o f t h e e q u a t o r i a l r a i n f o r e s t n a r r o w e d . E v e n in e q u a t o r i a l r e g i o n s e o l i a n sands w e r e deposited ( D E H E I N Z E L I N , 1 9 5 2 ) . O n l y in t h e z o n e o f t h e c l i m a t o l o g i c a l ( o r t h e r m a l ) e q u a t o r , s o m e degrees s o u t h w a r d o f t h e a s t r o n o m i c a l o n e , t h e t r o p i c a l r a i n forest c o u l d s u r v i v e . D u r i n g t h e i n t e r g l a c i a l s t h e c l i m a t i c b e l t s shifted a g a i n t o w a r d s t h e p o l e s ( c f . t h e d i a g r a m p u b l i s h e d b y F A I R B R I D G E in 1 9 6 1 a n d 1 9 6 4 ) . A l t h o u g h t h e shifting o f t h e c l i m a t i c b e l t s w a s n o t a s s i m p l e as i n d i c a t e d a b o v e , w e m a y a c c e p t t h a t in t h e N . S a h a r a the p l u v i a l p e r i o d s c o i n c i d e d with t h e g l a c i a l s b u t t h a t in t h e m o r e southern r e g i o n s , p l u v i a l p e r i o d s h a v e t o b e c o r r e l a t e d w i t h i n t e r g l a c i a l t i m e s . F o r t h e c o r r e s p o n d i n g regions in t h e N e w W o r l d , v i z . t h e C a r i b b e a n a n d t h e a d j a c e n t p a r t o f S o u t h - A m e r i c a i t seems w o r t h w h i l e t o g a t h e r t h e e q u i v a l e n t p a l a e o c l i m a t i c i n f o r m a t i o n in o r d e r t o l o o k f o r similar c o n c l u s i o n s , a l t h o u g h a d m i t t e d l y o u r k n o w l e d g e o f t h e Q u a t e r n a r y c l i m a t i c changes in t h i s p a r t o f t h e w o r l d is r a t h e r i n c o m p l e t e . I n this p a p e r d e d i c a t e d t o t h e m a s t e r o f q u a t e r n a r y research, P r o f . D r . P . W O L D S T E D T , w e w i l l a t t e m p t t o p r o v i d e a b r i e f i n v e n t a r i s a t i o n o n this s u b j e c t1) . P a l a e o c l i m a t i c c h a n g e s m a n i f e s t t h e m s e l v e s b y t h e f o l l o w i n g p h e n o m e n a : A . m o v e m e n t s o f the levels o f seas a n d l a k e s

B . c h a n g e s i n t e m p e r a t u r e o f t h e s e a w a t e r C . p e d o l o g i c a l changes, i n c r u s t r a t i o n s D . changes i n t h e v e g e t a t i o n

E . c h a n g e s i n g r o u n d w a t e r c o n d i t i o n s F . changes i n t h e g e o m o r p h o l o g i c a l p r o c e s s e s .

i ) T h e author is much indebted to Prof. J . B . B I R D , Montreal and D r . K. DUPHORN, Hannover, who kindly gave him some valuable references and to Mrs. M . VAN DER M A E S E N and D r . H . BOISSEVAIN, who corrected the manuscript linguistically.

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a d A . Q u a t e r n a r y m o v e m e n t s o f s e a l e v e l , m o s t l y r e c o r d e d b y fossil — e i t h e r e l e v a t e d or s u b m e r g e d — c o a s t l i n e s a n d t e r r a c e s , a r e c a u s e d b y t h e a c c r e t i o n o r m e l t i n g o f g r e a t masses o f i n l a n d i c e . T h e y h a v e n o d i r e c t r e l a t i o n w i t h l o c a l c l i m a t i c changes in r e g i o n s l i k e t h e C a r i b b e a n . Y e t t h e s t u d y o f f o r m e r l e a l e v e l s in this a r e a is v e r y i m p o r t a n t as it offers t h e p o s s i b i l i t y t o c o m p a r e t h e t i m i n g o f t h e l o c a l c l i m a t i c s e q u e n c e s w i t h t h o s e o f t h e e x t e n s i o n a n d s h r i n k i n g o f t h e g r e a t ice masses. I n t h e C a r i b b e a n a n d a l o n g t h e n o r t h c o a s t o f S o u t h A m e r i c a m a n y d a t a a r e a v a i l a b l e c o n c e r n i n g m a r i n e t e r r a c e s a n d s u b m a r i n e benches. I t is t r u e t h a t t e c t o n i c m o v e m e n t s w i l l h a v e c h a n g e d t h e o r i g i n a l h e i g h t o f s o m e o f these " w a t e r m a r k s " , e s p e c i a l l y t h e o l d e r o n e s . Y e t t h e i n f l u e n c e o f t h e c h a n g e d s e a l e v e l s , b o t h a b o v e a n d b e l o w t h e r e c e n t o n e is e v i d e n t . H i g h s e a l e v e l s i n d i c a t e d b y m a r i n e t e r r a c e s ( a b r a s i o n t e r r a c e s as w e l l as a c c u m u l a t i v e benches) h a v e b e e n m e n t i o n e d b y J U K E S B R O W N E a n d H A R R I S O N ( 1 8 9 1 ) , M O L E N -G R A A F F ( 1 9 2 9 ) , R U T T E N ( 1 9 3 2 ) , W E S T E R M A N N ( 1 9 3 2 ) , P I J P E R S ( 1 9 3 3 ) , Z O N N E V E L D ( 1 9 6 0 ) , D E B U I S O N J E ( 1 9 6 4 ) a n d m a n y o t h e r s . L o w s e a l e v e l s , e v i d e n c e d b y d r o w n e d v a l l e y -s y -s t e m -s a n d -s u b m a r i n e benche-s are d e -s c r i b e d e. g. b y M O L E N G R A A F F ( 1 9 2 9 ) a n d N O T A ( 1 9 5 8 ) . T h e s e w a t e r m a r k s a r e t h e m o r e v a l u a b l e i f — as is t h e case in s o m e i n s t a n c e s — a b s o l u t e d a t i n g s a r e a v a i l a b l e . N O T A , f o r i n s t a n c e , f o u n d t h a t his 4 0 a n d 1 2 f a t h o m l e v e l s off t h e A t l a n t i c c o a s t o f G u y a n a c o u l d b e d a t e d as resp. 1 1 . 0 0 0 a n d 8 . 0 0 0 y e a r s a g o , i . e . d u r i n g t h e l a t e - a n d p o s t g l a c i a l rise o f t h e s e a l e v e l . B R O E C K E R et a l . ( 1 9 6 7 ) s h o w t h a t in B a r b a d o s t h e l o w e r t h r e e e l e v a t e d t e r r a c e s o r i g i n a t e d b e t w e e n 8 2 . 0 0 0 a n d 1 2 2 . 0 0 0 y e a r s B . P . after e v a l u a t i o n o f t h e t e c t o n i c influence a n d c o m p a r i s o n w i t h t h e a v a i l a b l e d a t a c o n c e r n i n g s e a w a t e r t e m p e r a t u r e s in t h e a d j a c e n t seas ( E M I L I A N I , 1 9 6 5 , 1 9 6 6 ) . T h e a u t h o r s i n d e e d e v i d e n c e t h a t the h i g h s e a l e v e l s c o r r e s p o n d e d w i t h h i g h t e m p e r a t u r e s o f t h e s e a w a t e r a n d o c c u r r e d in a p e r i o d k n o w n as an i n t e r g l a c i a l ( t h e l a s t i n t e r g l a c i a l ) . I n A f r i c a t h e a n c i e n t c o a s t l i n e a l o n g t h e g r e a t l a k e s p l a y e d an i m p o r t a n t r o l e in t h e h i s t o r y o f p a l a e o c l i m a t i c research ( c . f. N I L S S O N , 1 9 3 1 ; K E N D A L L , 1 9 6 5 ) . I n n o r t h e r n S o u t h A m e r i c a o n l y t h e vicissitudes o f t h e ( f o r m e r ) L a k e o f B o g o t a , C o l o m b i a , c o u l d b e t a k e n in c o n s i d e r a t i o n (see ad D ) . a d B . E s p e c i a l l y t h e p u b l i c a t i o n s o f E M I L I A N I ( 1 9 6 5 , 1 9 6 6 ) a n d E R I C S O N C . S . , 1 9 6 4 ) g i v e i n t e r e s t i n g d a t a c o n c e r n i n g t h e c h a n g e s in t e m p e r a t u r e o f the C a r i b b e a n s e a w a t e r . A s h a s b e e n said b e f o r e , these d a t a c a n b e c o r r e l a t e d w i t h t h o s e c o n c e r n i n g h i g h e r a n d l o w e r s e a l e v e l s : h i g h sealevels p r o v e t o b e s y n c h r o n o u s w i t h high w a t e r - t e m p e r a t u r e s a n d v i c e v e r s a . a d C . U n d e r c e r t a i n c l i m a t i c c o n d i t i o n s d e p o s i t i o n o f c a r b o n a t e s ( a n d o t h e r m a t e r i a l s ) c a n result in t h e f o r m a t i o n o f t r a v e r t i n e masses o r caliches. W I L H E L M Y ( 1 9 5 4 ) m e n t i o n s suchlike fossil i n c r u s t a t i o n s in n o r t h e r n V e n e z u e l a , e s p a c i a l l y on t h e p e n i n s u l a o f G u a j i r a f o r w h i c h h e p o s t u l a t e s c l i m a t i c c o n d i t i o n s t h a t w e r e m o r e h u m i d t h a n t h e p r e s e n t ( v e r y d r y ) o n e s .

B A R K E R ( 1 9 6 0 ) f o u n d t h a t u n d e r t r o p i c a l r a i n f o r e s t , g r a n i t e s are a t t a c k e d b y c h e m i c a l w e a t h e r i n g in such a w a y t h a t m i n e r a l s l i k e e p i d o t e a n d h o r n b l e n d e p r a c t i c a l l y dis a p p e a r . I f , h o w e v e r , t h e forest is a b s e n t , these m i n e r a l s a r e resistant a g a i n s t w e a t h e r i n g . T h e s a m e a u t h o r m e n t i o n s t h e o c c u r r e n c e o f e p i d o t e a n d h o r n b l e n d e in a s a m p l e f r o m a l a t e r i t i c l a y e r in t h e h u m i d f o r e s t o f S u r i n a m a n d c o n c l u d e s t h a t t h i s m u s t p o i n t t o p a l a e o c l i m a t i c c o n d i t i o n s u n f a v o r a b l e f o r h u m i d t r o p i c a l f o r e s t s . a d D . A v e r y i m p o r t a n t i n d i c a t o r f o r p a l a e o c l i m a t e s is t h e v e g e t a t i o n ( a l t h o u g h it is k n o w n t h a t t h e v e g e t a t i o n n o t a l w a y s is a p t t o k e e p p a c e with t h e c l i m a t i c changes a n d t h a t s o m e t i m e s o t h e r f a c t o r s t h a n c l i m a t e m a y c a u s e v e g e t a t i o n a l c h a n g e s ) . U p t i l l n o w q u a t e r n a r y p a l a e o b o t a n i c a l d a t a a r e k n o w n f r o m C o s t a R i c a , C o l o m b i a a n d

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Quaternary climatic changes in the Caribbean and N . South-America 205 G u y a n a . I n C o s t a R i c a ( M A R T I N , 1 9 6 4 ) a n d C o l o m b i a ( V A N D E R H A M M E N a n d G O N Z A L E Z , 1 9 6 0 ) p o l l e n a n a l y s i s r e v e a l e d t h a t d u r i n g t h e g l a c i a l p e r i o d s the t i m b e r - l i n e in t h e m o u n t a i n s w a s some 1 0 0 0 m l o w e r t h a n a t p r e s e n t t i m e s . T h e last m e n t i o n e d a u t h o r s a l s o s h o w e d t h a t d u r i n g the p e r i o d s w i t h a h i g h t i m b e r - l i n e ( t h e i n t e r g l a c i a l s ) , t h e l e v e l o f t h e L a k e o f B o g o t a w a s l o w e r e d , a p p a r e n t l y d u e t o a d e c r e a s e o f t h e p r e c i p i t a t i o n . I n o t h e r w o r d s : i n t e r p l u v i a l s c o u l d b e c o r r e l a t e d w i t h i n t e r g l a c i a l s . F r o m t h e l o w l a n d s o f t h e L l a n o s o f C o l o m b i a a n d V e n e z u e l a no p a l a e o c l i m a t i c d a t a a r e k n o w n f r o m p l e i s t o c e n e t i m e s . W I J M S T R A a n d V A N D E R H A M M E N ( 1 9 6 6 ) a n a l y s e d s o m e p o l l e n o u t o f the L l a n o s O r i e n t a l e s o f C o l o m b i a , b u t the o l d e s t samples o n l y d a t e f r o m a p p r o x i m a t e l y 6 . 0 0 0 y e a r s B . P . I n G u y a n a t h e s a m e a u t h o r s i n v e s t i g a t e d a profile t h a t y i e l d e d s t r a t a as o l d as 9 . 0 0 0 — 1 0 . 0 0 0 B . P . T h e p o l l e n e v i d e n c e a p p e a r s t o p o i n t t o closed d r y f o r e s t o r c l o s e d s a v a n n a w o o d l a n d c o n d i t i o n s d u r i n g l a t e g l a c i a l t i m e s in a region t h a t n o w has a s a v a n n a c h a r a c t e r ( R u p u n u n i ) . P r o f . H I L L S o f M c G i l l U n i v e r s i t y , M o n t r e a l ( o r a l c o m m u n i c a t i o n ) , h o w e v e r , e x p l a i n e d t h a t t h e l a k e w h e r e t h e s a m p l e s w e r e t a k e n , is in fact a k i n d o f an o x b o w l a k e ; so it is n o t e x c l u d e d t h a t in f o r m e r t i m e s this l a k e h a d an open c o n n e c t i o n w i t h t h e I r e n g R i v e r . T h i s r i v e r d r a i n s a l a r g e a r e a c o v e r e d w i t h different t y p e s o f forests a n d s a v a n n a s . I n o t h e r w o r d s : t h e r e is a p o s s i b i l i t y t h a t p a r t o f t h e p o l l e n c o n t e n t o f the s a i d p r o f i l e e s p e c i a l l y o f the o l d e r p a r t , does n o t p r o v i d e i n f o r m a t i o n a b o u t the ( f o r m e r ) v e g e t a t i o n o f t h e p r o p e r s u r r o u n d i n g s b u t o f t h e (forest) v e g e t a t i o n o f h i g h e r p a r t s o f the d r a i n a g e basis o f t h e I r e n g R i v e r .

A l s o i n t h e c o a s t a l a r e a s o f G u y a n a V A N D E R H A M M E N ( 1 9 6 1 ) m a d e s o m e v e r y i n t e r esting i n v e s t i g a t i o n s . H e s h o w e d t h a t in t h e subsoil o f G e o r g e t o w n a s a v a n n a - l i k e v e g e t a t i o n c o u l d be c o r r e l a t e d w i t h a ( g l a c i a l ) l o w s e a l e v e l . A f t e r a rise o f t h e s e a l e v e l a ( m a n g r o v e ) v e g e t a t i o n c a m e i n t o the p i c t u r e . A c t u a l l y this m a n g r o v e v e g e t a t i o n itself does n o t p o i n t t o c l i m a t i c changes; it is a n e v i d e n c e f o r t h e ingression o f t h e sea u n d e r influence o f the rising s e a l e v e l . T h e s a v a n n a v e g e t a t i o n , h o w e v e r , c o u l d i n d i c a t e a c l i m a t e w i t h a treeless v e g e t a t i o n in an a r e a w h e r e in p r e s e n t t i m e s the n a t u r a l c o n d i t i o n s t e n d t o a h u m i d rain f o r e s t . a d E . T A M E R S ( 1 9 6 6 , 1 9 6 7 ) r e c e n t l y p u b l i s h e d some i n t e r e s t i n g d a t a c o n c e r n i n g the a g e o f g r o u n d w a t e r masses in the n e i g h b o u r h o o d o f M a r a c a i b o a n d o n t h e p e n i n s u l a of G u a j i r a i n N . W . V e n e z u e l a . I n t h e s e a r e a s , a t p r e s e n t , the p o t e n t i a l e v a p o r a t i o n is a p p r o x i m a t e l y f o u r t o five times h i g h e r t h a n the p r e c i p i t a t i o n . T h e r e f o r e r e c e n t r a i n w a t e r is n o t in a s i t u a t i o n t o reach t h e g r o u n d w a t e r r e s e r v o i r . R e c h a r g e o f the g r o u n d w a t e r basins c o u l d o n l y h a v e o c c u r r e d d u r i n g p e r i o d s w i t h m o r e p r e c i p i t a t i o n ( a n d p e r h a p s less e v a p o r a t i o n ) , i. e. during p l u v i a l p e r i o d s . A c c o r d i n g t o r a d i o c a r b o n d a t i n g s p u b l i s h e d b y T A M E R S ( 1 9 6 7 ) m o s t o f t h e g r o u n d w a t e r s a m p l e s in the n e i g h b o u r h o o d o f M a r a c a i b o a r e a p p r o x i m a t e l y 1 0 . 0 0 0 — 3 5 . 0 0 0 y e a r s o l d . T h e p l u v i a l p e r i o d d u r i n g w h i c h t h e recharge o f t h e a q u i f e r has t a k e n p l a c e e v i d e n t l y c o i n c i d e d w i t h t h e last ( W ü r m , Weichsel, W i s c o n s i n ) g l a c i a l p e r i o d . I n G u a j i r a T A M E R S ( 1 9 6 6 ) f o u n d ages in the r a n g e o f 5 . 0 0 0 — 8 . 0 0 0 y e a r s , t h e t i m e o f t h e H o l o c e n e c l i m a t i c o p t i m u m . H e c o n c l u d e s t h a t h e r e the g r o u n d w a t e r r e s e r v o i r c o u l d h a v e been c h a r g e d during a p l u v i a l t h a t c o u l d c o r r e s p o n d w i t h t h e p e r i o d o f h i g h e r p r e c i p i t a t i o n r e c o g n i z e d b y B U T Z E R ( 1 9 6 1 ) in t h e M e d i t e r r a n e a n r e g i o n s . ad F . F i n a l l y some g e o m o r p h o l o g i c a l p h e n o m e n a m a y p o i n t t o a l t e r n a t i o n s o f p l u v i a l a n d i n t e r p l u v i a l p e r i o d s in the C a r i b b e a n a n d t h e n o r t h e r n p a r t o f S o u t h A m e r i c a . W I L H E L M Y ( 1 9 5 4 ) c a l l e d a t t e n t i o n t o t h e " f o s s i l " c h a r a c t e r o f the v a l l e y s o f C u r a c a o which w o u l d reflect c o n d i t i o n s m o r e h u m i d t h a n those o f r e c e n t times.

O n B o n a i r e and B a r b a d o s B L U M E ( 1 9 6 8 ) c o u l d e s t a b l i s h t h a t a l o n g t h e f r o n t o f s o m e c u e s t a - l i k e f o r m s s l u m p i n g a n d spring e r o s i o n must h a v e o c c u r r e d u n d e r c l i m a t i c c o n ditions c o n s i d e r a b l y m o r e h u m i d than a t p r e s e n t .

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T R I C A R T a n d C A I L L E U X ( 1 9 6 5 ) r e c o r d a n o b s e r v a t i o n o n B a r b a d o s w h e r e a l a r g e l i m e s t o n e b l o c k w h i c h d u r i n g a h u m i d p e r i o d w a s m o v e d d o w n w a r d b y s l u m p i n g , w a s r e c e n t l y a t t a c k e d b y s e a l e v e l s o l u t i o n . T h e l o c a l s i t u a t i o n leads t h e m t o c o n c l u d e t h a t t h e s l u m p i n g t o o k p l a c e d u r i n g t h e last g l a c i a l p e r i o d w h e n t h e sealevel w a s l o w e r t h a n a t p r e s e n t . A v e r y i n t e r e s t i n g s t u d y w a s c a r r i e d o u t b y D E B U I S O N J E ( 1 9 6 4 ) w h o p o s t u l a t e s t h a t s o m e m a r i n e t e r r a c e s ( r e p r e s e n t i n g f r i n g i n g a n d b a r r i e r r e e f s b u i l t up d u r i n g p e r i o d s w i t h h i g h s e a l e v e l s ) w e r e f o r m e d u n d e r r e l a t i v e l y a r i d c o n d i t i o n s . M o r e o v e r , h e f o u n d e v i d e n c e t h a t t h e l o w e r s e a l e v e l s c o i n c i d e d w i t h m o r e h u m i d p e r i o d s . R e c e n t l y G A R N E R ( 1 9 6 7 ) e x p r e s s e d t h e i d e a t h a t t h e i n t r i c a t e systems o f r a p i d s a n d w a t e r f a l l s t h a t a r e c h a r a c t e r i s t i c f o r m a n y r i v e r s in V e n e z u e l a ( a n d o t h e r t r o p i c a l r e g i o n s ) w o u l d b e c o n n e c t e d w i t h a t r a n s i t i o n f r o m d r y t o h u m i d c o n d i t i o n s : t h e r i v e r s t h a t h a d o r i g i n a t e d d u r i n g t h i s t r a n s i t i o n w o u l d n o t y e t h a v e h a d t h e o p p o r t u n i t y t o d e g r a d e t h e i r b e d s a n d w o u l d o n l y find t h e i r w a y in u n c o n c e n t r a t e d a n d u n o r g a n i z e d c h a n n e l systems ( " r i v e r s in t h e m a k i n g " ) . I n m y o p i n i o n , h o w e v e r , this v i e w is based o n a m i s c o n c e p t i o n c o n c e r n i n g t h e e v o l u t i o n a n d c h a r a c t e r o f r i v e r s in h u m i d t r o p i c a l r e g i o n s ( c f . Z O N N E V E L D , 1 9 5 2 , 1 9 6 8 ; T R I C A R T , 1 9 5 9 ; B A R K E R , 1 9 6 0 ) . T h e o b s e r v a t i o n s , m a d e b y G A L O N ( 1 9 6 6A, 1 9 6 6B) a r e m o r e i m p o r t a n t in t e r m s o f p a l a e o c l i m a t i c e v i d e n c e . G A L O N r e f e r s t o e r o s i o n a l f o r m s which a p p a r e n t l y w e r e m o u l d e d u n d e r s e m i a r i d c o n d i t i o n s ( h e f o u n d t h e s a m e " b r a n c h e d slope i n c i s i o n s " in a c t i o n in a c t i o n in s e m i - a r i d r e g i o n s ) b u t w h i c h in p r e s e n t d a y s a r e c o v e r e d w i t h t r o p i c a l r a i n f o r e s t . A l s o Z O N N E V E L D ( 1 9 6 7 ) m e n t i o n s fossil l a n d f o r m s in southern S u r i n a m , r e s e m b l i n g fossil " l a v a k a s " , w h i c h m u s t h a v e o r i g i n a t e d in p e r i o d s o f g r e a t e r e x t e n s i o n o f t h e s a v a n n a s ( a c t u a l l y a l a r g e p a r t o f t h e r e c e n t s a v a n n a s in t h a t a r e a h a s t o b e r e g a r d e d as a n t h r o p o g e n i c ) . "When t h e d a t a r e v i e w e d a r e o v e r l o o k e d a n d c o n s i d e r e d , it b e c o m e s e v i d e n t t h a t t h e v a l u e o f t h e i n f o r m a t i o n is u n e q u a l . S o m e d a t a o n l y i n d i c a t e t h a t a t o n e t i m e o r t h e o t h e r c l i m a t i c changes d i d o c c u r , p a r t l y in r e g i o n s t h a t a r e n o w r e l a t i v e l y d r y ( C u r a c a o , B o n a i r e , N . W . V e n e z u e l a a n d also B a r b a d o s ) , p a r t l y in t h e regions w i t h h u m i d t r o p i c a l c l i m a t e s (the n o r t h e r n p a r t o f S o u t h A m e r i c a ) .2) O n t h e o t h e r h a n d o t h e r d a t a p r o v i d e m o r e e x a c t i n f o r m a t i o n a n d c o n c e r n t h e r e l a t i o n b e t w e e n l o c a l c l i m a t i c changes a n d t h e s e q u e n c e o f g l a c i a l s a n d i n t e r g l a c i a l s . T h e e v i d e n c e o f C u r a c a o ( D E B U I S O N J E , 1 9 6 4 ) , C o l o m b i a ( V A N D E R H A M M E N a n d G O N Z A L E Z , 1 9 6 0 ) , B a r b a d o s ( T R I C A R T a n d C A I L L E U X , 1 9 6 5 ) a n d M a r a c a i b o ( T A M E R S 1 9 6 7 ) c l e a r l y p o i n t t o h u m i d c o n d i t i o n s d u r i n g t h e last g l a c i a l ( o r p a r t o f i t ) a n d t o ( r e l a t i v e ) a r i d i t y d u r i n g i n t e r g l a c i a l s . T h e e v i d e n c e f r o m G u y a n a a n d S u r i n a m , h o w e v e r , is s t i l l insufficient t o e s t a b l i s h t h e c l i m a t i c e v o l u t i o n in t h a t a r e a , a l t o u g h t h e a v a i l a b l e d a t a seem t o i n d i c a t e t h a t i n t h e G u y a n a s t h e least h u m i d c o n d i t i o n s c o i n c i d e d w i t h g l a c i a l s . T h i s w o u l d m e a n t h a t d u r i n g t h e t r a n s i t i o n f r o m a n i n t e r g l a c i a l t o a g l a c i a l p e r i o d t h e ( s e m i - ) a r i d z o n e shifted s o u t h w a r d a n d t h a t it w e n t b a c k a g a i n w h e n t h e g l a c i a l w a s s u c c e e d e d b y t h e n e x t i n t e r g l a c i a l . T h i s w o u l d c o r r e s p o n d w i t h a shifting o v e r s o m e 1 0 d e g r e e s . A t p r e s e n t it is p r e f e r a b l e t o a v o i d s p e c u l a t i o n a n d t o w a i t f o r t h e results o f n e w r e s e a r c h t o b e c a r r i e d o u t in eastern V e n e z u e l a , n o r t h e r n B r a z i l a n d t h e t h r e e G u y a n a s .

2) One would expect that also in French G u y a n a such indications will be found, in spite o f the

information already given by CAILLEUX ( 1 9 5 9 ) that in this country during the Pleistocene ap parently no important climatic changes had occurred.

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Quaternary climatic changes in the Caribbean and N . South-America 207

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Anschrift des Verf.: Prof. Dr. J . I. S. Zonneveld, Utrecht, Drift 2 1 , Geografisch Instituut der Rijksuniversiteit, Utrecht, Nederland.