Periglacial Eolian Evenly Laminated Sandy Deposits in the Late Pleistocene of Nw Europe, A Facies Unrecorded in Modern Sedimentological Handbooks

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PERISLACIAL EOLIAN E V E N L Y LAMINATED SANDY DEPOSITS IN THE LATE PLEISTOCENE OF N'4 E U R O P E , A F A C I E S U N R E C O R D E D IN MODERN SEDIMENTOLOGICAL HANDBOOKS

G E R A R D H.J. R U E G G ( G e o l o g i c a l Survey of The N e t h e r l a n d s , Box 157,

2000 AD Haarlem, The N e t h e r l a n d s )

INTRODUCTION P u b l i c a t i o n s on sandy e o l i a n d e p o s i t s in t h e world mostly concern dune d e p o s i t s , t h e dominant s e d i m e n t a r y s t r u c t u r e of which i s c r o s s bedding ( t o low-angle bedd i n g ) . Regional sand s h e e t s - n o t a s i n t e r d u n e a r e a s - a r e a much l e s s f r e q u e n t f a c i e s and have been s t u d i e d much l e s s o f t e n . The paragraph t h a t Reineck & Singh (1980) devoted t o sand s h e e t s w i t h o u t pebble l a y e r s runs as f o l l o w s : "There a r e v a s t a r e a s of sand s h e e t s known which a r e devoid o f any kind of p e b b l e s . Such sand s h e e t s a r e made u p of w e l l - s o r t e d e o l i a n sand w i t h well developed h o r i z o n t a l l y laminated s a n d . A combination of r a p i d s e d i m e n t a t i o n , high wind v e l o c i t i e s and f a i r l y uniform g r a i n s i z e o f t h e sand cause d e p o s i t i o n of s h e e t sand with an abundantly developed e v e n l y laminated sand bedding ( c f . Bagnold 1954a; Glennie 1970) 'I.

Hunter (1977) mentions t h e p r o d u c t i o n of "planebed l a m i n a t i o n " by winds of 40 mi l e s p e r hour ( 1 8 m / s e c ) . F r y b e r g e r e t a l . ( 1 9 7 9 ) d e s c r i b e r e c e n t low-angle e o l i a n d e p o s i t s of a sand s h e e t , o c c u r r i n g as a t r a n s i t i o n a l f a c i e s between high-angle e o l i a n dunes and non-eolian d e p o s i t s , n e a r Great Sand Dunes National Monument, Colorado, U.S.A. They l i s t e l e v e n s e d i m e n t a r y f e a t u r e s . Most of t h e s e f e a t u r e s a r e a l s o p r e s e n t i n an e o l i a n s u b f a c i e s under c o n s i d e r a t i o n ( s e e below); g e n e r a l l y , however, f e a t u r e s r e l a t e d t o b i o l o g i c a l a c t i v i t y a r e very s c a r c e in t h i s subf a c i e s in t h e European d e p o s i t s .

The Parsonsburg Sand i n t h e C e n t r a l Delmarva P e n i n s u l a , Maryland and Delaware, d e s c r i b e d by Denny e t a l . ( 1 9 7 9 ) , presumably r e p r e s e n t s a f o s s i l analogue in North America. A r e c e n t d e p o s i t from Banks I s l a n d shown in F i g . 8 of a paper by P i s s a r t e t a l . (1977) i s h i g h l y comparable t o a Dutch p e r i g l a c i a l e o l i a n subf a c i e s ( s u b f a c i e s A , see below), although e v i d e n t l y the Banks I s l a n d d e p o s i t c o n t a i n s abundant o r g a n i c laminae ( f r a g m e n t s of willow s h r u b s ) in c o n t r a s t t o t h e bulk of t h e Dutch d e p o s i t s ; t h e d e p o s i t on Banks I s l a n d seems t o be r e l a t i v e l y s m a l l , and connected with r i v e r v a l l e y s . S i m i l a r ( s u b ) r e c e n t d e p o s i t s seem t o

o c c u r on Cumberland P e n i n s u l a , B a f f i n I s l a n d ( c f . Thompson 1954, c i t e d in Andrews e t a l . 1979 and i n Dyke e t a l . 1 9 8 2 ) .

456

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F i g . 1. Map o f The N e t h e r l a n d s s h o w i n g l o c a t i o n s r e f e r r e d t o i n Legends t o t h e f i g u r e s ( l e f t ) , and map o f NW E u r o p e ( r i g h t ) . REGIONAL SETTING Deposits o f t h i s k i n d d a t i n g from t h e Weichselian stage (equivalent t o the W i s c o n s i n s t a g e ) o c c u r i n n o r t h e r n F r a n c e (Somm6 e t a l . 198O), B e l g i u m ( e . 9 . M a r 6 c h a l & M a a r l e v e l d 1955; de P l o e y 1961; Zagwi j n & Paepe 1968; Vandenberghe & Gul l e n t o p s 1977; Vandenberghe 1981), West Germany (Dewers 1932, 1934; Ducker & M a a r l e v e l d 1957; Ruegg 1 9 8 1 ) , E a s t Germany ( N e u m e i s t e r 1971; see a l s o Eissmann 1 9 8 1 ) , P o l a n d ( e . g . K o z a r s k i e t a l . 1969; Nowaczyk 1976; K o z a r s k i 1980) and p r e s u m a b l y a l s o i n t h e USSR ( F i g . 1 ) . I n t h e e a s t e r n p a r t o f t h i s s a n d - b e l t ,

the

d e p o s i t s a r e p r e d o m i n a n t l y p r e s e n t as dune f i e l d s r e l a t e d t o r i v e r ( p r a d o l i n a ) v a l l e y s (Nowaczyk 1976; K o s t e r 1 9 8 2 ) .

I n The N e t h e r l a n d s , p e r i g l a c i a l d e p o s i t s a r e known f o r a t l e a s t s i x g l a c i a l stages (Fig. 2 ) . Important c o n t r i b u t i o n s concerning t h e occurrence, stratigraphy,

457 d a t i n g , and g e n e s i s o f p e r i g l a c i a l ! d e i c h s e l i a n d e p o s i t s have been p u b l i s h e d by, e . g . van d e r Hammen

(1951), van d e r Hammen h V a a r l e v e l d ( 1 9 5 2 ) , ) 4 a r @ c h a l &

M a a r l e v e l d (1955), D u c k e r 7, r l a a r l e v e l d ( 1 3 5 7 ) , Z a g w i j n ( 1 9 6 1 ) , van den T o o r n ( 1 9 6 7 ) , van d e r Hammen e t a l . ( 1 9 6 7 ) , Z a g w i j n & Paepe ( 1 9 6 8 ) , van d e r Hammen & Wijmstra (eds.) (1971), Bisschops (1973), Zagwijn (1974), Maarleveld (1976), K o l s t r u p & W i j m s t r a ( 1 9 7 7 ) , K o l s t r u p ( 1 9 8 0 ) , Vandenberghe ( 1 9 8 1 ) , Vandenberghe & Krook ( 1 9 8 1 ) and K o s t e r ( 1 9 8 2 ) . T h e r e i s a g e n e r a l agreement a b o u t t h e e o l i a n dominated o r i g i n o f t h e s e d e p o s i t s ,

a t p r e s e n t known as t h e Twente F o r m a t i o n .

The d e p o s i t s i n q u e s t i o n d r a p e an i r r e g u l a r t o p o g r a p h y ( g e n e r a l f i e l d name: c o v e r s a n d s ) ; on a r e g i o n a l s c a l e t h e y f o r m s a n d s h e e t s . The d e p o s i t s o c c u r o v e r l a r g e a r e a s , n o r m a l l y as a b l a n k e t w i t h a t h i c k n e s s o f some d e c i m e t e r s t o some m e t e r s ; t h e y a r e a b s e n t o n l y on e l e v a t e d a r e a s where t h e y may n o t have been dep o s i t e d , and i n c e r t a i n l o w r e g i o n s due t o s u b s e q u e n t e r o s i o n . The l a t e r a l and v e r t i c a l r e l a t i o n s as w e l l as t h e r e l a t i v e abundances o f t h e d i s t i n g u i s h e d sub-

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Chronostratigraphy

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F i g . 2. L e f t : Q u a t e r n a r y c h r o n o s t r a t i y r a p h y o f The N e t h e r l a n d s s h o w i n g t h e i n t e r v a l s (hatched) i n which p e r i y l a c i a l d e p o s i t s were formed. R i g h t : c h r o n o s t r a t i g r a p h y and c l i m a t i c c u r v e o f t h e W e i c h s e l i a n ( a f t e r van S t a a l d u i n e n e t a l . 1 9 7 9 ) .

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F i g . 3. C r o s s - s e c t i o n through t h e Y o n t f e r l a n d ice-pushed r i d g e in t h e eastern p a r t of t h e c e n t r a l Netherlands ( a f t e r van de Meene 1 9 7 7 ) . f a c i e s a r e s t r o n g l y dependent on t h e morphology of t h e s u b s o i l , which permits d i v i s i o n of The N e t h e r l a n d s i n t o a n o r t h e r n , a c e n t r a l , and a southern coversand a r e a . Moreover, t h e r e i s a l s o r o u g h l y a general i n c r e a s e of s i l t f r a c t i o n from N N W t o SSE; in t h e southernmost p a r t of t h e c o u n t r y only l o e s s d e p o s i t s occur.

I n a c o n s i d e r a b l e p a r t of t h e n o r t h e r n a r e a a g e n e r a l l y t h i n cover of periglacial Weichselian d e p o s i t s i s s e p a r a t e d from i d e n t i c a l d e p o s i t s of S a a l i a n age ( E i n d h o ven Formation) by a S a a l i a n b a s a l t i l l ; moreover, v a l l e y f i l l s o c c u r , in which s i g n i f i c a n t l o c a l - f l u v i a l d e p o s i t s may be p r e s e n t . I n t h e c e n t r a l p a r t , the subs t r a t u m was p r e v i o u s l y modelled by t h e S a a l i a n i n l a n d i c e and by Eemian interg l a c i a l l e v e l l i n g p r o c e s s e s ( m a i n l y niarine s e d i m e n t a t i o n in t h e former glacial b a s i n s ) ; h e r e , t h e Twente Formation, predominantly r e p r e s e n t e d by e o l i a n deposits, shows s t r o n g v a r i a t i o n of t h e t h i c k n e s s , r a n g i n g from some t e n s of meters in the

459

former g l a c i a l basins t o n i l l o c a l l y on the ice-pushed ridges ( F i g . 3 & Towards the German border, l o c a l - f l u v i a l s h e e t l i k e i n t e r c a l a t i o n s proportionally increase.

I n t h e southern p a r t of the coversand area, the existence of a horst and graben system i s strongly r e f l e c t e d in the extent and thickness of the p e r i g l a c i a l deposits (where the frequency o f the various subfacies i s largely u n k n o w n ) ; in the Central Graben thicknesses up t o 40 meters are known f o r the stacked p e r i g l a c i a l deposits of the l a s t t h r e e g l a c i a l stages ( E l s t e r i a n , Saalian, Weichselian: Nuenen Group) (Fig. 4 ) . More t o the west, f l a t areas with a cover of eolian dep o s i t s are i n t e r s e c t e d by valley f i l l s in which flowing-water sediments are present.

Fig. 4. Variations i n t h e thickness of the Nuenen Group, sheet 51 East ( a f t e r Bisschops 1973) and sheet 51 West ( J . P . Broertjes, Geological Survey, pers. comm.).

I n many areas of t h e country, these deposits are present a t the surface, and have been l i t t l e affected by Holocene processes. Often a so-called "coversand r e l i e f " i s present, with elevations mostly not exceeding 2 t o 3 , and in no case 5, meters in height (Koster 1982) (Fig. 5 ) . SEDIMENTARY (SUE) FACIES The following four subfacies can be distinguished within the p e r i g l a c i a l dep o s i t s of The Netherlands and adjacent areas: (1) eolian subfacies A , ( 2 ) eolian subfacies 6, ( 3 ) l a c u s t r i n e subfacies, and ( 4 ) flowing-water subfacies ( l o c a l

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F i g . 5 . Ridges of Late Weichselian coversand on t h e s u r f a c e of a former g l a c i a l basin ( G e l d e r s e V a l l e i ) ; 1. b r o o k s , 2 . coversand r i d g e , 3. ice-pushed r i d g e ( a f t e r Maarlevel d 1 9 6 0 ) . d i s c h a r g e ) . The l i t h o l o g i c a l and s t r u c t u r a l c h a r a c t e r i s t i c s w i l l be mentioned b r i e f l y ; t h e photographs supplement t h e d e s c r i p t i o n s . Eolian s u b f a c i e s A ( s e e F i g s . 6-11) Predominantly unimodal w e l l - s o r t e d uniform s a n d s ; e v e n l y l a m i n a t e d , o f t e n with a " f l o w i n g " appearance w i t h t a p e r i n g u n i t s and low-angle c o n t a c t s ; r a r e l y cross-bedded; o c c a s i o n a l l y with laminae composed of g r a n u l e s o r small p e b b l e s ( m o s t l y w i n d - p o l i s h e d , l e s s commonly as v e n t i f a c t s ) ; l o c a l l y c r a c k s and small i n t e r n a l f r o s t wedges, t h i n moss-peat i n t e r c a l a t i o n s and adhesion r i p p l e l a y e r s a r e p r e s e n t ; i n t e r n a l c r y o t u r b a t i c l e v e l s a r e o f t e n l e s s numerous and t h i n n e r than t h o s e a s s o c i a t e d w i t h t h e n e r t s u b f a c i e s ( c f . Maarleveld 1 9 7 6 ) ; b u r i e d accumulations a r e very i n f r e q u e n t ; v a r i o u s low r e l i e f forms (Maarleveld 1960) inay be a s s o c i a t e d . Where c o a r s e sediment was a v a i l a b l e ( e . g . , n e a r ice-pushed r i d g e s ) , laminae o r l e n s e s ( t h e l a t t e r p o s s i b l y r e p r e s e n t i n g degraded g r a n u l e r i p p l e s ; c f . Bagno d 1941, p . 1 5 5 ) c o n t a i n i n g g r a n u l e s o r small p e b b l e s may o c c u r , as well a s l e v e l s

461 w i t h uniformly dispersed gravel-sized p a r t i c l e s ( c f . Bagnold 1941, p . 159). These

phenomena may a l s o be encountered in r e l a t i v e l y coarse eolian subfacies B deposits Note: the deposits depicted by Ahlbrandt & Fryberger (1982) in t h e i r Figs. 18C a n d 18D, show much resemblance t o eolian subfacies A deposits (except f o r the bioturbation t r a c e s , not present in the l a t t e r ) .

Eolian subfacies B ( s e e Figs. 11-20) I n t e r c a l a t e d yellowish a n d greyish evenly laminated sands ( " l a y e r cake" e f f e c t ) ; greyish laminae are more or l e s s s i l t y ; minor grain-size peaks occur the coarse s i I t and/or

in

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f r a c t i o n s ; i n t e r n a l c r y o t u r b a t i c levels

and f r o s t wedges are commonly p r e s e n t . Whaleback-like low-relief forms may consist of t h i s tyue of deposit (de Jong 1975). Locally, the following f e a t u r e s may be found: t h i c k e r s i l t y layers w i t h a loess o r loess-approaching grain s i z e ( m a i n peak

in

the coarse s i l t or

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the 75-88ym f r a c t i o n s ) , peat l a y e r s , and adhesion

r i p p l e l a y e r s ; " v e r t i c a l - p l a t y " crack systems ( c f . V i n k & Sevink,

in

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Hammen & Wijmstra 1971) may be preserved. Note: the often v i s i b l e c r i n k l y appearance

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eolian subfacies B deposits ( s e e

Figs. 12-17) i s t h e r e s u l t of contortion by freeze/thaw action on previously e x i s t i n g laminae, and i s not caused by i n f i l t r a t i o n of very finesdeveloping d i s s i p a t i o n s t r u c t u r e s as defined by Ahlbrandt & Fryberger 1980, 1982. Lacustrine subfacies ( s e e Figs. 21-24) Varying composition of d e p o s i t s ; sandy p a r t s are evenly or wave-ripple laminated; s i l t layers composed of material w i t h a loess or l o e s s - l i k e grain s i z e and g y t t j a layers may be i n t e r c a l a t e d ; frost-thaw and f r o s t s t r u c t u r e s occur r a r e l y . Flowing-water subfacies ( s e e Figs. 25-29) Cross-bedded and cross-laminated deposits ( t h e l a t t e r made by among other things climbing r i p p l e s i n d i c a t i n g declining current v e l o c i t i e s ) , represented by p e r s i s t e n t layers as well as by complex c h a n n e l - f i l l s ; cross-bedded cosets locally contain macoscopic p l a n t remains (reworked), e s p e c i a l l y in c h a n n e l - f i l l s . This subfacies i s a t t r i b u t e d t o local discharge systems, as distinguished from the f l u v i a l deposits of t h e trunks of t h e Rhine-Meuse r i v e r system. RELATION OF SUBFACIES IN TIME A N D PLACE

Although the Twente Formation i s eolian-dominated, a t l e a s t in most of the exposures, l a c u s t r i n e a n d flowing-water deposits play an important r o l e l o c a l l y . Grain-size i n v e s t i g a t i o n s have shown t h a t the water-laid deposits are generally reworked eolian sediments. Many authors ( e . g . van der Hammen e t a l . 1967; Vandenberghe 1981) found a c o r r e l a t i o n between f a c i e s a n d subdivision of the g l a c i a l s t a g e . D u r i n g the Early

462

F i g . 6 . E o l i a n s u b f a c i e s A d e p o s i t showing even l a m i n a t i o n , d e f l a t i o n levels and f r o s t c r a c k s ( a g e : Late ! ! e i c h s e l i a n ) ( r o d s c a l e i n cm); Claricurri, Closterineent .

F i g . 7 . Eolian s u b f a c i e s A d e p o s i t s ( a g e : Late I l e i c h s e l i a n ) o v e r l y i n g Saalian t i l l ; e o l i a n accumulation l e v e l l e d by subsequent e o l i a n d e p o s i t i o n ( l e n g t h o f j o i n t e r 3 3 c m ) ; E r i c a , n e a r Crnmen, motorvay c r o s s i n g .

F i g . 8. E o l i a n subfacies A sedivent (I!eicflselian) o v e r l y i n g Saalian sandur deoosits ( r u l e r l e n g t h 2 5 crn); Z e i s t , rnotorway c r o s s i n g .

F i g . 9. D e t a i l o f upuer sediment i n F i g . 8 ( h e i g h t 27 cri).

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464

F i g . 11. Eolian s u b f a c i e s A sediment o v e r l y i n g e o l i a n s u h f a c i e s R d e p o s i t s . The former- i s v i r t u a l l y f r e e of s i l t and more s u s c e p t i b l e t o wind a c t i o n ; ldeelde ( B e l g i u m ) , sand p i t .

465

F i g . 1 2 . Eolian s u b f a c i e s R sediments with a f a i n t v e r t i c a l - p l a t y crack system ( a g e : ivliddle W e i c h s e l i a n ) . The h e i g h t o f t h e l a c q u e r p e e l i s 7 7 cm; L o s s e r , Dinkel v a l l e y , o u t c r o p i n concave bank.

466

F i g . 13. E o l i a n s u b f a c i e s 3 sediments ( a g e : ' l i d d l e l i e i c h s e l i a n ) ; t h e lower part i s c r y o t u r h a t i c a l l y deformed a n d tonord by a r e o i o n a l d e f l a t i o n l e v e l (Ceuningen % r a v e l 3ed); t h e unper p a r t c o n t a i n s s o m e i n t e r c a l a t i o n s l a i d down by flowing water- ( h e i y l i t o f l a c q u e r p e e l : 35 c m ) ; L o s s e r , D i n k e l valley, o u t c r o p i n concave bank,

F i a . 1 4 . F o l i a n s u h f a c i e s " sediments ,"iit'i a consrlicLioii5 i r l t r a f o r m a t i o n a l minor c r y o t u r b a t c d a n d s l i c h t l y s l t i m ~ ?l r i v e l ( a n c : ',li;idle L'leichselian). T'ie h e i g h t o f t h e l a c q u e r p e e l i s 35 ci'1 an3 t h e depth of t h e d p n o s i t i s a b o u t 1 2 . 5 ~1 !ielo./ s i i r f a c Q l c w l ; Voorthuizen, sand p i t .

F i ? . 1 5 . Eolian s u b f a c i e s E sediments s h o ' v i n g

i m n y c r y o t u r b a t e d l e v e l s ( a g e : ' l i d d l e I4eiciiseli a n ) . 'Jete s p e c i f i c s u r f a c e p a t t e r n i n f l u e n c e d b y v e r t i c a l - v l a t y crack systems ( r u l e r 33 ciii l o n q ) . ? e D o s i t s i t u a t e d a b o u t 1 5 ni belo:.i s u r f a c e l e v c l ; ' i o o r t l i u i r e n , sand D i t .

e m v

4 68

F i g . 1 7 . Major c r y o t u r b a t i c a l d e f o r m a t i o n s i n mainly e o l i a n s u b f a c i e s E s e d i m e n t s ; Uitwel l i n g e r g a , aquaduct p i t .

c a s t irl c!olian s u b facias r sedimc'nts ( a w o f t l i e d e q o s i t i s S a a l i a n , age of t h e c a s t i s : ! e i c t i s e l i a n ) ( I i e i g i i t o f lacqirer p e e l : ?.$1 m ) ; Sevenuni, S c h a t h e r p s a n d ; l i t . F i g . 19. Ice-:/edqe

470

F i g . 20. V e r t i c a l - n l a t y Lrrick s y i t e n i v i s i b l e iri e o l i a n S u b f a L i P i C ietiiiiients a b o i r t 1 0 . 5 in below s u r f a c e l i ? v i ' l ( a s p : Y i d t l l ~ : ' : I p i i I . i 5 e l i a n ~ ( r i i l e r : 3') c r l o n s ) ; Voorttiuizi'n, s a n d p i t .

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2 1 . D-noiits o f t h e l a c u s t r i n e ii.i'>facies; s i l t , i and f i n e sands ,:iitii l m t i c u l a r anri w a v y h e d d i n q ( t i e i o l i t : 45 c v ) ; 7irirl1ioven, r a i l v a y - t u n n e l p i t

Fin.

F i g . 2 2 . L a c u s t r i n e d e p o s i t s showing f i n e sands, s i l t s and g y t t j a , i n t e r s e c t e d by ice-wedge c a s t s ( a b o u t R in b e l o w O . D . ; Middle !.!eictiselian); Den t i e l d e r , d o c k yard p i t .

472

F i g . 23. D e p o s i t s of t h e l a c u s t r i n e s u b f a c i e s , with h a l f - s t a t i o n a r y : i ~ v t ? r i p p l e c o s e t s ; a t ttie b a s e t h e r e a r e d e b r i s flow sedirnents )with remnants of t h e o r i g i n a l sediment resembling ttie o v e r l y i n g d e p o i i t s (about, 10 111 b e l o w O.D.; Middle Weictiselian) ( s c a l e on spade s h a f t in drii); Deri l l e l d e r , dockyard lit.

F i g . 2 4 . D e t a i l o f F i g . 2 3 ( j o i n t e r measures 33 crri).

473

F i q . 2 5 . Flowing-'qater deposits intprcalated w i t h eolian subfacies C deposits (aoe: "iddle ' ! e i c h s e l i a n ) ; l a c q u e r o e e l ranoe 4.4Q-5.SQm !)elow s u r f a c e l e v e l ; Voor-ttiuizen, s a n d p i t .

F i g . 2 6 . I n t e r c a l a t i o n of s h e e t l i k e flowino-:vatcr d e 9 o s i t s i n eolian iiibfacies 4 deonsits; Overdinki'l, s a n d o i t..

474

F i q . 2 7 . C h a n n e l - f i l l s i n c i s e d i n a c r y o t u r h a t i c a l l y d e f o r m e d s u p e r n o s i t i o n of p e r i g l a c i a l l a c u s t r i n e d e p o s i t s , Eemian p e a t , and S a a l i a n p e r i g l a c i a l deposits; Cindhoven, r a i l w a y - t u n n e l n i t .

F i g . 28. C h a n n e l - f i l l w i t h a b u n d a n t p l a n t m a t e r i a l l o c a l l y and p e a t lumps a t the base, i n c i s e d i n e o l i a n s u b f a c i e s R d e p o s i t s s i t u a t e d a b o u t 9 m below O.D. (age: M i d d l e W e i c h s e l i a n ) ; Den H e l d e r , d o c k y a r d p i t .

475

F i g . 29. C r o s i - l a m i n a t e d d e p o s i t l a i d down b y f l o w i n g w a t e r \which have f i l l e d up s h a l l o w c h a n n e l - f i l l s ; a b o u t 16 m h e l o w 0.D. ( a g e : E a r l y ' l e i c h s e l i a n ) ( r u l e r i n crn); Den i i e l d e r , d o c k y a r d p i t . and l a t e W e i c h s e l i a n , m a i n l y l o a m - f r e e c o v e r s a n d s were d e p o s i t e d ,

hereas d u r i n g

t h e M i d d l e W e i c h s e l i a n ( P l e n i g l a c i a l ) m a i n l y loamy c o v e r s a n d s were f o r m e d . Van den T o o r n ( 1 9 6 7 ) f o u n d a s i m i l a r s u p e r p o s i t i o n i n t h e graben a r e a ; he d e s c r i b e d an a n a l o g o u s s e t t i n g f o r t h e u n d e r l y i n g S a a l i a n p e r i g l a c i a l d e p o s i s ( E i n d h o v e n F o r m a t i o n ) . M a a r l e v e l d ( 1 9 7 6 ) s u g g e s t e d t h a t t h e " O l d e r Coversands

(Middle

Weichselian; g e n e r a l l y e o l i a n s u b f a c i e s B ) arose under permafrost c o n d i t i o n s and t h e "Younger C o v e r s a n d s " ( L a t e W e i c h s e l i a n ;

generally e o l i a n subfacies A)

were d e p o s i t e d i n t h e absence o f p e r m a f r o s t . W i t h r e s p e c t t o t h e f o u r s u b f a c i e s , i t appears t h a t d e p o s i t s o f s u b f a c i e s A d o m i n a t e d i n t h e E a r l y and L a t e W e i c h s e l -

i a n s e d i m e n t a t i o n , whereas t h e o t h e r t h r e e s u b f a c i e s d o m i n a t e d u n d e r p l e n i g l a c i a l c o n d i t i o n s . The p r e s e n c e o r absence o f p e r m a f r o s t m i g h t a l s o e x p l a i n why s h e e t s o r c h a n n e l s were f o r m e d w i t h i n t h e f l o w i n g - w a t e r s u b f a c i e s . D e p o s i t s o f t h e l a c u s t r i n e and f l o w i n g - w a t e r s u b f a c i e s seem t o be i m p o r t a n t i n t h e southern coversand area, v i z . ,

t h e C e n t r a l Graben a r e a . Here, t h i c k l e n s e s

o f sandy s i l t ( i n c r o s s - s e c t i o n s up t o more t h a n 10 km w i d e and up t o 5 m t h i c k ) o c c u r ( " B r a b a n t s i l t " ) ( v a n den T o o r n 1967; B i s s c h o p s 1 9 7 3 ) , w h i c h a r e c o n s i d e r e d t o be d e p o s i t s f o r m e d by e o l i a n s u p p l i e d m a t e r i a l i n s h a l l o w s h e e t s o f s t a n d i n g water i n areas w i t h blocked r u n - o f f .

476 SEQUENTIONAL TRENDS The f o l l o w i n g gradual s u p e r p o s i t i o n s ( o r p a r t s of them) have been observed:

+

eolian subfacies A eolian subfacies B

.f

eolian subfacies A

t

and

eolian subfacies B

+

+

(lacustrine subfacies)

1a c u s t r i ne s ubf a c i e s

flowing-water subfacies I n v e s t i g a t i o n of a Weichselian v a l l e y f i l l l e d t o a s c h e m a t i c r e p r e s e n t a t i o n of an " i d e a l " p e r i g l a c i a l sequence b u t h e r e w i t h o u t l a c u s t r i n e d e p o s i t s - shown now i n F i g . 30 ( F i g . 2 i n Ruegg 1 9 7 5 ) .

v

H

DESERT PAVEMEN1

G

DRY EOLIbN

F

MOlST EOLIAN

E

WET EOLIAN

D

WATER CURRENT V E L O C l T I LOW TO NIL

c 6

&

R&TT*ER F I S T R U N N I N G WATER R IPPLE PHASE LOW ENERGY

FAST RUNNING WATER DUNE P W S E LOW ENERGY (OFTEN ASSENT)

V E R I FbST RUNNING WbTER HIGH ENERGY

a h k A 7 5L

Fig. 30. Schematic r e p r e s e n t a t i o n of a p e r i g l a c i a l sequence as deduced from d e p o s i t s i n a v a l l e y f i l l n e a r P e e l o , The N e t h e r l a n d s . The lower d i v i s i o n s ( A - D ) were formed under d e c l i n i n g c u r r e n t v e l o c i t y c o n d i t i o n s and t h e upper p a r t ( E - H ) was g e n e r a t e d mainly s u b a e r i a l l y and under i n c r e a s i n g e o l i a n i n f l u e n c e ; l a c u s t r i n e d e p o s i t s a r e n o t p r e s e n t and c r y o t u r b a t i c d e f o r m a t i o n s a r e r a t h e r s c a r c e ( a f t e r Ruegg 1 9 7 5 ) .

G R A I N SIZE F i g . 31 shows t y p i c a l g r a i n - s i z e p o p u l a t i o n s found i n samples of e o l i a n subf a c i e s A and 6. The p a t t e r n of the l a t t e r i s c h a r a c t e r i z e d by t h e o c c u r r e n c e of peaks i n the c o a r s e - s i l t and 7 5 - 8 8 ~ mf r a c t i o n s . As an a s p e c t s of t h e i n v e s t i g a t ion performed f o r t h e c l a s s i f i c a t i o n of Dutch Holocene s o i l s , c a r r i e d o u t by the S o i l Survey I n s t i t u t e ( d e Bakker & S c h e l l i n g 1 9 6 6 ) , a g r a i n - s i z e continuum was found between p e r i g l a c i a l e o l i a n sands and s i l t s ( i n c l u d i n g l o e s s ) ( F i g . 3 2 ) .

477 F i g . 31. R e p r e s e n t a t i v e g r a i n s i z e h i s t o g r a m s f o r e o l i a n subf a c i e s A ( u p p e r t h r e e ) and eolian subfacies B (lower three deposits.

BLA RlCUM

z.

2

&

0‘

u-u

“

2

i

s -

0-2um

F i g . 32. P r o p o r t i o n s of c l a y , s i l t , and sand in samples from t h e coversand and l o e s s a r e a in The N e t h e r l a n d s ( a f t e r de Bakker & Schelling 1966).

478

TENTATIVE EXPLANATION OF THE EOLIAN SUBFACIES The f o l l o w i n g g e n e r a l remarks d e a l w i t h t h e e o l i a n environment of d e p o s i t i o n . The f i r s t three u n d e r l i n e t h e predominantly n o n - f l u v i a l o r i g i n , and t h e l a s t t h r e e c o n s i d e r t h e e o l i a n s e d i m e n t a t i o n i n more d e t a i l .

1. The more o r l e s s uniform h a b i t u s coupled w i t h the o v e r a l l o c c u r r e n c e and v a r i e g a t e d palaeotopography, as w e l l as t h e kind of s u r f a c e r e l i e f , argue a g a i n s t a f l u v i a l mode of o r i g i n . 2 . The absence of c r o s s bedding and c r o s s l a m i n a t i o n and the dominance of even l a m i n a t i o n , i n combination w i t h t h e f i n e - g r a i n e d l i t h o l o g y , cannot be exp l a i n e d i n terms of f l o w i n g - w a t e r p r o c e s s e s . 3. The d i s t u r b a n c e s c o n s i d e r e d t o be c r y o g e n e t i c a r e g e n e r a l l y u n l i k e disturbances seen i n w a t e r - l a i n n o n - p e r i g l a c i a l d e p o s i t s , as Maarleveld (1976) a l r e a d y concluded f o r " d r o p l i k e r e g u l a r d e f o r m a t i o n s " and G u l l e n t o p s & P a u l i s s e n (1978) f o r a kind of "drop s o i l " . 4. Organic l a y e r s o r r o o t d i s t u r b a n c e s a r e g e n e r a l l y s c a r c e o r a b s e n t , c o n t r a r y t o the s i t u a t i o n i n ( s u b ) r e c e n t e v e n l y laminated d e p o s i t s on Banks I s l a n d ( P i s s a r t e t a l . 1977) and B a f f i n I s l a n d ( e . g . , Dyke e t a l . 1 9 8 2 ) . 5 . On t h e b a s i s of the c r y o t u r b a t i c s t r u c t u r e s , p o l a r d e s e r t c o n d i t i o n s a r e inf e r r e d f o r p a r t of t h e Middle Weichselian ( P l e n i g l a c i a l ) . Twice a complete d i s a p p e a r a n c e of p e r m a f r o s t has been deduced from t h e o c c u r r e n c e of two major d i s t u r b e d l e v e l s ( e . g . , Maarleveld 1 9 7 6 ) . 6 . M e l t i n g - o u t of snow l e a d s t o d i s t u r b a n c e s of v a r i o u s s c a l e s , u p t o complete homogenization ( d i a m i c t i z a t i o n ) , b u t t h i s f e a t u r e i s v i r t u a l l y a b s e n t in the i n v e s t i g a t e d d e p o s i t s . On t h e c o n t r a r y , t h e g e n e r a l l y very s h a r p and cons p i c u o u s l a m i n a t i o n , w i t h laminae i n p l a c e s t r a c e a b l e l a t e r a l l y f o r more t h a n 10 m e t e r s , e x c l u d e s such p r o c e s s e s as m e l t i n g - o u t and a l s o e r o s i o n on a micros c a l e due t o r u n - o f f . The f o l l o w i n g t e n t a t i v e h y p o t h e s i s c o n c e r n i n g t h e d e p o s i t i o n of sandy and s i l t y laminae has been proposed ( c f . Ruegg 1975, 1 9 8 1 ) : pure s a n d laminae : d e p o s i t s from t h e t r a c t i o n c a r p e t on a d r y s e d i m e n t a t i o n surf ace; s i l t y s a n d laminae: a s t h e f o r e g o i n g , b u t s u s p e n s i o n load may s t i c k t o a somet i m e s damp s e d i m e n t a t i o n s u r f a c e ; s i l t layers

: wet d e p o s i t i o n a l s u r f a c e ; t r a c t i o n c a r p e t f i x e d upwind; only

the s u s p e n s i o n load reached t h e s p o t . An i n f l u e n c e of t h e humidity of t h e s e d i m e n t a t i o n s u r f a c e on l o e s s deposition has been d e m o n s t r a t e d by Cegla (1969, 1972; c f . Smalley 1 9 7 5 ) . French ( 1 9 7 6 ) d i s c u s s e d the p o s s i b l e d i f f e r e n c e s between t h e P l e i s t o c e n e perig l a c i a l environment of m i d - l a t i t u d e s and t h a t of p r e s e n t - d a y l a t i t u d e s from a

479 g e o m o r p h i c p o i n t o f v i e w . F o r t h e f o r m e r , he a s s i g n e d i m p o r t a n c e t o t h e r e g i m e o f d i u r n a l s o l a r r a d i a t i o n which l e d t o greater m o b i l i t y o f t h e s u r f i c i a l material He a l s o i n f e r r e d s t r o n g e r w i n d s . The g r e a t i m p o r t a n c e o f w i n d s i s c o n c l u d e d f r o m t h e presumed e x i s t e n c e o f g r e a t e r w i n d g r a d i e n t s due t o t h e s p a t i a l c o n c e n t r a t i o n o f t h e v a r i o u s c l i m a t i c zones. I n a d d i t i o n , a n t i c y c l o n i c c o n d i t i o n s p r e v a i l i n g above t h e e x t e n d e d i c e s h e e t s were p r e s u m a b l y much more s e v e r e . F r e n c h m e n t i o n e d t h e abundance o f s u i t a b l e m a t e r i a l a r i s i n g f r o m t h e i c e - m a r g i n a l p o s i t i o n o f t h e P l e i s t o c e n e p e r i g l a c i a l zone. Because o f t h e c o l d e r c l i m a t e and t h e r o u t e o f t h e w e s t e r l i e s , he supposed a r e l a t i v e l y l o w l e v e l o f p r e c i p i t a t i o n . However, t h i s does n o t a c c o u n t f o r t h e d i f f e r e n c e i n t h e d e g r e e o f P l e i s t o c e n e p e r i g l a c i a l dep o s i t i o n i n N o r t h A m e r i c a ( a s f a r as p u b l i s h e d ) v e r s u s NW Europe. S t r o n g subs i d e n c e and t h e a v a i l a b i l i t y o f an abundance o f s u i t a b l e m a t e r i a l i n an e x t e n s i v e d e l t a i c s e t t i n g i n t h e w e s t e r n p a r t o f t h e l a t t e r r e g i o n m u s t have been i m p o r t a n t contributory factors. CONCLUSIONS I n t h e NW p a r t o f c o n t i n e n t a l Europe, s t r e t c h i n g f r o m n o r t h e r n F r a n c e t o t h e B a l t i c s t a t e s o f t h e USSR, t h e r e i s a l a r g e s a n d - b e l t o f w i n d - d o m i n a t e d d e p o s i t s g e n e r a l l y devoid o f h i g h angle cross-beds formed d u r i n g g l a c i a l stages b u t n o t d i r e c t l y r e l a t e d t o i n l a n d i c e . I n The N e t h e r l a n d s t h e s e d e p o s i t s o r i g i n a t e d i n a t l e a s t s i x g l a c i a l s t a g e s ; s t a c k e d sequences a r e l o c a l l y up t o 40 m e t e r s t h i c k . S i g n i f i c a n t d e p o s i t i o n took p l a c e d u r i n g t h e l a s t g l a c i a l stage; a t present, d e p o s i t s o f t h e l a t t e r s t a g e c o v e r a t l e a s t i n The N e t h e r l a n d s an a r e a o f a p p r o x i m a t e l y 30,000 s q km. A f a c i e s w i t h even l a m i n a t i o n shows s t r o n g l a t e r a l e x t e n s i o n and i s r o u g h l y

concordant w i t h t h e p r e - e x i s t i n g topography ("coversands").

Two s u b f a c i e s have

been r e c o g n i z e d , one w i t h a n d t h e o t h e r w i t h o u t more o r l e s s s i l t y l a m i n a e ; t h e f o r w r i s p a r t o f a c o n t i n u u m o f w h i c h t h e l a t t e r and l o e s s a r e t h e endmembers. The t w o s u b f a c i e s a r e t h o u g h t t o be e o l i a n , r e p r e s e n t i n g e n v i r o n m e n t s w i t h a l t e r n a t i n g w e t and d r y d e p o s i t i o n a l s u r f a c e s o r o n l y d r y d e p o s i t i o n a l s u r f a c e s . Moreo v e r , l o c a l - f l u v i a l and l a c u s t r i n e d e p o s i t i o n a l s o t o o k p l a c e i n t h i s p e r i g l a c i a l environment. The f r e q u e n t o c c u r r e n c e o f t h e s e d e p o s i t s i n The N e t h e r l a n d s and a d j a c e n t a r e a s i s c l e a r l y r e l a t e d t o r e g i o n a l s u b s i d e n c e combined w i t h e x t e n s i v e d e l t a - b u i l d i n g , w h i c h l e d t o an abundance o f s u i t a b l e m a t e r i a l . I n E a s t Germany and P o l a n d , t h e p e r i g l a c i a l deposition i s predominantly r e s t r i c t e d t o broad f l u v i a l v a l l e y s , e s p e c i a l l y t h o s e o f W e i c h s e l i a n p r a d o l i n a s ; t h e r e , dune f i e l d s a r e t h e d o m i n a n t phenomenon. C l i m a t o l o g i c a l l y , t h e d i u r n a l s o l a r r a d i a t i o n p a t t e r n as w e l l as t h e e x i s t e n c e o f s t r o n g m i d - l a t i t u d e w e s t e r l i e s m u s t have been i m p o r t a n t f a c t o r s .

I n t h e s c a r c e l i t e r a t u r e c o n c e r n i n g e v e n l y l a m i n a t e d e o l i a n sand s h e e t s , t h i s

480 f a c i e s i s t h o u g h t t o be r e l a t e d t o t h e a v a i l a b i l i t y o f abundant m a t e r i a l , h i g h w i n d v e l o c i t i e s , and u n i f o r m g r a i n s i z e . ACKNOWLEDGEMEN T S I thank: t h e D i r e c t o r o f t h e Netherlands G e o l o g i c a l Survey f o r p e r m i s s i o n t o

c a r r y o u t t h e i n v e s t i g a t i o n s ; J. Vandenberghe and J. Schwan f o r d i s c u s s i o n s i n t h e f i e l d ; W.H.

Zagwijn,

J.G.

Zandstra, E.A.

K o s t e r , 3. Vandenberghe and T.S.

A h l b r a n d t f o r c r i t i c a l r e a d i n g o f t h e m a n u s c r i p t ; Mrs. A.C.H.M.

Niessen f o r h e l p

w i t h l i t e r a t u r e , e s p e c i a l l y f r o m P o l a n d ; F . W i l l e m s e n f o r some p h o t o g r a p h s , A . K o e r s f o r p r e p a r a t i o n o f t h e d r a w i n g s ; M r s . I. Seeger f o r r e a d i n g t h e E n g l i s h

text,

and Mrs. M . E . I .

Jouini f o r typing.

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