ROAD RESEARCH LABORATORY

Ministry of Transport

RRL REPORT NO. 39

STUDIES OF THE KEUPER M A R L :

GEOLOGY AND GEOGRAPHY

by

M J. Dumbleton and G. West

CROWTHORNE

ROAD RESEARCH LABORATORY

1966

CONTENTS

A b s t r a c t

1. I n t r o d u c t i o n

2. C h a r a c t e r and o r ig in of the depos i t s

3. D i s t r i b u t i o n and o c c u r r e n c e in eng inee r ing works

4. D e s c r i p t i o n of the K eupe r M a r l ou tc rop

4 .1 Nor r th -eas t e rn a r m

4 . 2 C e n t r a l r eg ion

4 . 3 The t a i l

4 . 4 N o r t h - w e s t e r n a r m

5. Soil, e leva t ion , r a i n f a l l and d r a i n a g e

6. C o n c l u s i o n s

7. R e f e r e n c e s

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(~ C R O W N COPYRIGHT 1966

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STUDIES OF THE KEUPER M A R L :

GEOLOGY AND GEOGRAPHY

ABS TRAC T

This r e p o r t is the f i r s t of s e v e r a l dea l ing with the geology, geography , mine ra logy and chemica l and phys i ca l p r o p e r t i e s of the Keuper Mar l . It d e s c r i b e s i ts geologica l or ig in , c h a r a c t e r and d i s t r i bu t i on , and the cond i - t ions under which it is encoun te red in e n g i n e e r i n g works .

The Keuper Mar l was depos i ted in an in land bas in having i n t e r n a l d ra inage and a hot c l ima t e . It is g e n e r a l l y r e d d i s h - b r o w n and is m a d e up of p a r t i c l e s of quar tz , c a rbona t e s and c lay m i n e r a l s . It ou t c rops i n p l a in s and at m o d e r a t e e levat ions , m o r e than half below 200 ft . Ra infa l l v a r i e s f r o m 22.5 in per y e a r in the eas t to over 35 in in the wes t . W e a t h e r i n g produces soil often too heavy for a r ab l e use .

A map shows the d i s t r ibu t ion of the Keuper M a r l and the a p p r o x i - mate extent of dr i f t cover . The ou tc rop c o v e r s s o m e 5000 s q u a r e m i l e s , occupying much of Central England, with a r m s extending to the Nor th Sea, the I r i sh Sea, and the Engl i sh Channel . Dr i f t depos i t s c o v e r n e a r l y al l of the n o r t h - e a s t e r n and n o r t h - w e s t e r n a r m s , and about half the c e n t r a l region and the s o u t h - w e s t e r n a r m . The Keuper Mar l m a y be e n c o u n t e r e d in eng ineer ing works not only w h e r e it is exposed at the su r f ace , but a l s o in excava t ions and dur ing p i l e -d r iv ing th rough o v e r l y i n g dr i f t d e p o s i t s and th rough the younger over ly ing r o c k s a long the e a s t e r n b o r d e r of the outcrop.

I. INTRODUCTION

The civil eng ineer is conce rned with the o c c u r r e n c e and c h a r a c t e r i s t i c s of the va r ious sol id and dr i f t depos i t s which cons t i tu t e the land s u r f a c e , and the r e l a t i o n between them, because they a r e encoun te red in the c o n s t r u c t i o n of cu t t ings , e m b a n k - men t s and foundat ions . The Keuper Mar l was s e l e c t e d fo r s tudy b e c a u s e it has an extensive outcrop in Southern Br i t a in including a r e a s of c u r r e n t r o a d m a k i n g ac t iv i ty , and because it shows a number of unusual phys i ca l c h a r a c t e r i s t i c s which have g iven r i s e to d i f f icu l t ies both during tes t ing and on s i t e .

This note r ev iews the geology and geography of the Keupe r Mar l . The geo log ica l mode of or ig in of the Keuper Mar l accounts fo r the way in which it o c c u r s at the s u r - face of the ear th , and makes c l e a r the r e l a t i on be tween it and o the r d e p o s i t s wi th which it is a s soc ia t ed . A map is p r e s e n t e d (Fig. 1.) showing the extent of d r i f t c o v e r of the solid outcrop. The geological o r ig in of the Keupe r M a r l a l so a c c o u n t s fo r c h a r a c t e r i s t i c s such as i ts f ine pa r t i c l e s ize and p r e d o m i n a n t l y r e d co lou r , the p r e - sence in it of occas iona l bands of c o a r s e r - g r a i n e d m a t e r i a l , g y p s u m or sa l t , and the const i tut ion of the mine ra l p a r t i c l e s of which it is c o m p o s e d .

G e o g r a p h i c a l f e a t u r e s of the ou tc rop such as re l i e f , ra infa l l , the qual i ty of the land and i t s u s e by man, a r e c o n s i d e r e d b e c a u s e they indica te some of the env i ron- m e n t a l cond i t i ons which will be e n c o u n t e r e d in r o a d works on the Keuper Mar l in d i f f e r e n t p a r t s of the coun t ry .

F u r t h e r r e p o r t s wil l d e a l w i t h inves t iga t ion of the mine ra logy of the Keuper M a r l and of i t s c h e m i c a l and phys i ca l c h a r a c t e r i s t i c s , p a r t i c u l a r l y those that affect i t s u s e in c iv i l eng inee r ing .

2. CHARACTER AND ORIGIN OF THE DEPOSITS

The K e u p e r M a r l is be t t e r d e s c r i b e d as a muds tone than as a m a r l because it is not p r e d o m i n a n t l y c a l c a r e o u s , and in i t s n a t u r a l s t a t e it is not in the usua l phys i ca l con- d i t ion of a c l ay . Mos t of it i s da rk r e d or r e d d i s h - b r o w n but l o c a l l y - o c c u r r i n g green or g r e y b l o t c h e s and bands g ive s o m e beds a v a r i e g a t e d appea rance . The h ighes t beds in the s u c c e s s i o n , the T e a Green M a r l s , a r e a l m o s t en t i r e ly g reen in colour , which m a y i n d i c a t e a change in e n v i r o n m e n t t owards the end of the per iod.

M i n e r a l o g i c a l l y the Keupe r M a r l is a m i x t u r e of clay m i n e r a l s and f ine p a r t i c l e s of qua r t z , d o l o m i t e and ca l c i t e . S t r ings and nodules of gypsum a re common, while in p l a c e s t h i c k e r d e p o s i t s of v a r i o u s m i n e r a l s a l t s a r e found, including gypsum (CaSO 4. 2H20) , ha l i t e (NaCI)_. and c e l e s t i n e (SrSO4). Thin h a r d e r bands of sandstone or s i l t - s tone known as s k e r r i e s a l so o c c u r at i n t e r v a l s .

The K e u p e r M a r l o c c u r s at the top of the T r i a s s i c s y s t e m which, in Br i ta in , com- p r i s e s a l o w e r B u n t e r and an uppe r Keuper s e r i e s . The Bunter cons i s t s of sand- s tones and pebb l e -beds ; the Keupe r is g e n e r a l l y f i n e r and c o n s i s t s of s ands tones and m a r l s . The r e l a t i o n s h i p of the Keuper M a r l to o lde r and younger geological depos i t s is shown in Fig . 2.

At the c l o s e of the C a r b o n i f e r o u s p e r i o d an episode of mounta in-bu i ld ing ea r th m o v e m e n t s le f t B r i t a i n as p a r t of a l a rge , moun ta inous cont inenta l land m a s s . In the subsequen t denuda t ion , d e b r i s was swept down to l o w e r - l y i n g a r e a s , pa r t ly by wind ac t ion and p a r t l y by t o r r e n t s , to f o r m the c o a r s e b r e c c i a s and cong lomera t e s of the P e r m i a n s y s t e m and the l a t e r Bun te r s a n d s t o n e s and pebble -beds . As wea the r ing p r o c e s s e s con t i nued and b e c a m e l e s s i n t ense the c o a r s e s ed imen t s gave p lace at f i r s t to f i n e - g r a i n e d sands and l a t e r to s i l t s . These accumula t ed in b road pla ins and now c o m p r i s e the Keupe r Sands tone below and the Keuper M a r l above. Ca rbona te s w e r e c o n s e r v e d , and sa l t depos i t s i nd i ca t e that t e m p o r a r y sa l t lakes were fo rmed . T h e s e s a l t depos i t s , the s c a r c i t y of f o s s i l s , the p r edominan t ly r ed colour and the f ine g r a i n - s i z e of the m a r l s , when t aken toge the r , ind ica te that d e s e r t condi t ions ex i s ted in B r i t a i n du r ing the l a t t e r p a r t of the Keupe r per iod .

At the end of K e u p e r t i m e s a m a r i n e t r a n s g r e s s i o n took place over the Keuper p la in as shown by the s u c c e e d i n g Rhae t i c beds and Lower L i a s c lays which contain m a r i n e f o s s i l s . U l t i m a t e l y t h e s e and l a t e r ove r ly ing depos i t s we re e roded and this exposed the p r e s e n t ou t c rop of the so l id Keuper Marl , some of which has s ince been c o v e r e d by d r i f t d e p o s i t s . The exposed s u r f a c e of the Keuper Mar l has been subjec t - ed to the p r o c e s s e s of w e a t h e r i n g and soi l f o r m a t i o n .

2

3. DISTRIBUTION AND OCCURRENCE IN ENGINEERING WORKS

A genera l v iew of the d i s t r ibu t ion of the Keuper Mar l m a y be ob ta ined f r o m the Geological Map of Grea t Br i t a in (Geological Survey, about 1 in to 10 mi l e s ) 1 but th is map shows only the sol id geology, omi t t ing the s u p e r f i c i a l o r d r i f t depos i t s which cover much of the su r f ace of the count ry . More de ta i l s can be ob ta ined f r o m the Geological Survey maps (1 in o r 6 in to the mile) , which m a y be ava i l ab l e in Solid or Drif t edi t ions. A m o r e g e n e r a l view of the a p p r o x i m a t e ex ten t of d r i f t c o v e r has r ecen t ly become avai lable in the map of supe r f i c i a l depos i t s in the At l a s of Br i t a in , (1 in to 16 mi les ) , -2 and an account of how the map was p r e p a r e d has been given by Clayton. 3 A map of the ou tc rop of the Keuper M a r l f o r m a t i o n in Sou the rn B r i t a i n with an indicat ion of the a p p r o x i m a t e extent of d r i f t c o v e r (Fig. 1.) has been c o m p i l e d by combining the data of t he se two maps . (Note: The a r e a m a p p e d a s Keuper M a r l includes the r e l a t i ve ly thin Dolomi t ic C o n g l o m e r a t e and R h a e t i c beds . )

The outcrop is in the f o r m of a "y" having a n o r t h - e a s t e r n a r m r e a c h i n g the North Sea at Middlesbrough, a n o r t h - w e s t e r n a r m which i s b roken into d e t a c h e d a r e a s the m o s t n o r t h e r l y of which is in Cumber land , a l a r g e c e n t r a l a r e a , in the Midlands, and a ta i l extending s o u t h - w e s t to the Engl i sh Channe l in Devon with a smal l branch in South Wales . The a r e a of the ou t c rop w a s e s t i m a t e d to be about 5000 square m i l e s . About o n e - t h i r d of the cen t r a l a r e a and t a i l of the ou t c rop and nea r ly all i ts e a s t e r n and w e s t e r n a r m s a r e c o v e r e d wi th s u p e r f i c i a l m a t e r i a l , t e r m e d drift , which inc ludes boulder clay, g lac ia l g rave l , r i v e r g r a v e l and a l luv ium, blown sand, and peat.

The Keuper Mar l will be encoun te red in eng inee r ing w o r k s w h e r e it i s f r e e f r o m super f ic ia l depos i t s , and it may a lso occur in excava t i ons and be r e a c h e d du r ing p i le -dr iv ing ope ra t ions where dr i f t cove r s it o r w h e r e it d ips u n d e r the y o u n g e r over ly ing rocks , a lmos t en t i r e l y Rhaet ic and L o w e r L ias , wh ich f l ank the e ~ s t e r n borde r of the outcrop f r o m Y o r k s h i r e to Devon. However , K e u p e r M a r l wi l l not be encountered in engineer ing works in the o lder r o c k s which l ie to the wes t of i t s out - crop or f o r m in l i e r s within it. T h e s e o lder r o c k s a r e the K e u p e r and B u n t e r Sand- s tones to the wes t of the n o r t h - e a s t e r n a r m , c e n t r a l a r e a and t a i l of the ou tc rop , and around the de tached a r e a s that f o r m the n o r t h - w e s t e r n a r m . They give p lace to s t i l l o lder rocks in Monmouthsh i r e and G l a m o r g a n s h i r e . The c e n t r a l a r e a of the o u t c r o p encloses a l a r g e in l ie r of Keuper and Bunter Sands tones and Coal M e a s u r e s .

4. DESCRIPTION OF THE KEUPER MARL OUTCROP

Informat ion on the geology and geography of the Keuper M a r l ou tc rop , and the con - di t ions encoun te red in the va r ious p a r t s of the coun t ry in wh ich i t o c c u r s , is g iven in the re levant handbooks on the Regional Geology of Grea t B r i t a i n , 4,5, 6,7 the Memoi r s to the 1-in maps of the Geological Survey, the P l a n n i n g Maps i , 8, 9,10, 12,12 (Ordnance Survey, about 1 in to 10 mi les ) , and the books of She r lock , 13 Wi l l s24 ,15 and Wells and Kirka ldy . 26

4.1 N o r t h - e a s t e r n a r m

In Not t inghamshi re about half the ou tc rop is c o v e r e d with d r i f t i nc lud ing the r i v e r g rave l and a l luv ium of the T r e n t Val ley. N o r t h w a r d s the o u t c r o p is a l m o s t e n t i r e l y

d r i f t - c o v e r e d , wi th a l l uv ium in n o r t h - w e s t L i n c o l n s h i r e giving p lace to g lac ia l gravel in the Eas t Riding of Y o r k s h i r e and the south of the Nor th Riding and then to Boulder C l a y f u r t h e r nor th .

In no r th L i n c o l n s h i r e the Keupe r M a r l a v e r a g e s 850 to 900 ft thick, and is des- c r i b e d 4 as d a r k r e d m a r l y c l ay wi th thin s k e r r i e s of r e d and, in the lower par t , grey s a n d s t o n e s . The s k e r r i e s c o n s i s t of s e a m s of g rey m a r l and g r e y dolomit ic sand- s t o n e s or s i l t s t o n e s . Nodu la r and l e n t i c u l a r m a s s e s of gypsum of c o m m e r c i a l value o c c u r loca l ly at two l eve l s ; K e u p e r M a r l u s e d as f i l l for the Newark B y - p a s s ea r th - w o r k s was ob ta ined f r o m g y p s u m work ings . The Is le of Axholme is an i so la t ed t r ac t of Keuper M a r l which has r e s i s t e d denudat ion . Nor th of the Humber , Tea Green M a r l s o c c u r at the top of the K e u p e r Mar l .

4 . 2 C e n t r a l r eg ion

The c e n t r a l r eg ion of the Keupe r M a r l ou tc rop is a b road a r e a occupying much of c e n t r a l England. About o n e - h a l f of it is c o v e r e d with drif t , r i v e r g rave l and a l luvium o c c u r r i n g in the v a l l e y s of the T r e n t , Soar and Avon, and boulder clay with occas iona l p a t c h e s of g l ac i a l g r a v e l on the h i g h e r ground. The a r e a s of inter-mediate e levat ion t end to be f r e e of d r i f t c o v e r .

A f a i r l y th ick d e v e l o p m e n t of sands tone , a s s o c i a t e d with b l u e - g r e y sha les , o c c u r s in the K e u p e r M a r l of W o r c e s t e r s h i r e , W a r w i c k s h i r e and G l o u c e s t e r a h i r e about 120 to 150 ft below the top of the fo rma t ion , and a t t a ins a th ickness of some 40 ft. Th i s i s the A r d e n Sands tone , 5 one of the Upper Keuper Sandstones of Cen t ra l Eng land which give r i s e to undu la t i ng topography, as in the F o r e s t of Arden.

4 .3 The t a i l

The ta i l of the ou t c rop th in s a long the Seve rn Valley and spl i t s , one b ranch following the n o r t h e r n s h o r e of the Mouth of the Severn , the o ther r e a c h i n g the Engl ish Channel in E a s t Devon. In W o r c e s t e r s h i r e and G l o u c e s t e r s h i r e the Keupe r Mar l is r e l a t ive ly d r i f t - f r e e excep t fo r the r i v e r g r a v e l and a l luv ium of the Severn and Teme va l l eys . F u r t h e r south, a l l uv ium c o v e r s the a r e a f lanking the Mouth of the Severn and the b r o a d v a l l e y s of the Axe and the P a r r e t t in Somerse t , and t h e r e is a cover of lowland pea t in S e d g e m o o r . The K e u p e r M a r l is exposed on the h igher ground and in l e s s l o w - l y i n g v a l l e y s , such as t h o s e which cut th rough the ove r ly ing Greensand of the Blackdown Hi l l s in S o m e r s e t and Devon.

In the C a r d i f f d i s t r i c t about 400 ft of Red Mar l s pas s upwards into 25 to 30 ft of T e a Green M a r l s . 6 In S o m e r s e t and in the B r i s t o l a r e a the Tea Green M a r l s a re s u c c e e d e d b y the G r e y M a r l s , and both a r e r e l a t i ve ly thin. 7 Ce le s t ine occu r s in the K e u p e r M a r l in G l o u c e s t e r s h i r e , w h e r e it i s worked c o m m e r c i a l l y .

4 . 4 N o r t h - w e s t e r n a r m

The n o r t h - w e s t e r n a r m of the K e u p e r M a r l outcrop c o n s i s t s of a number of s epa ra t e a r e a s , the m o s t n o r t h e r l y of wh ich is in Cumber land , to the wes t of Ca r l i s l e . All

T A B L E 1

E leva t ion and r a i n f a l l in the K e u p e r M a r l a r e a

Loca t i on E1 eva t ion Ra in fa l l

E a s t e r n a r m

Most of the a r e a

N. W. L i n c o l n s h i r e

Hambledon Hi l l s , N. Riding of Y o r k s h i r e

Cen t r a l a r e a

Most of the a r e a

Va l leys of T r e n t , Soar and Avon

Higher g round

Tai l

The Seve rn v a l l e y in W o r c e s t e r s h i r e and G l o u c e s t e r s h i r e

Monmouth

G lamorgan

Vale of Taunton, Va l ley of P a r r e t t , S e d g e m o o r

Other l o w - l y i n g coas t a l a r e a s , and lower v a l l e y s

F lanks of Mendip and Blackdown Hi l l s

W e s t e r n a r m

S. L a n c a s h i r e , C u m b e r l a n d

B a r r o w - i n - F u r n e s s , L a n c a s h i r e

C h e s h i r e P la in

N. Sh ropsh i r e

N. C h e s h i r e

Below 200 ft

200 to 400 ft

Below 200 ft

Above 400 ft

Below 200 ft

Below 200 ft

Ris ing to o v e r 400 ft

Below 200 ft

Ris ing to 400 ft

Below 200 ft

Below 200 ft

Mainly be low 200 ft

Ris ing above 200 ft

Ris ing above 200 ft

22 .5 to 25 in

Be low 22 .5 in

Ove r 25 in

25 to 2 7 . 5 i n

Below 25 in

May e x c e e d 30 in

25 to 2 7 . 5 i n

35 in

Up to 50 in

27 .5 to 30 in

F r o m 30 in to o v e r 40 in

30 to 35 in

O v e r 35 in

27 .5 in

27 .5 in

30 in

t h e s e a r e a s a r e a l m o s t e n t i r e l y c o v e r e d with dr i f t cons i s t ing of boulder c lay wi th • a r e a s of g l ac i a l g r a v e l in C h e s h i r e , F l i n t s h i r e and Shropsh i re , boulder clay, a l luvium and blown sand in L a n c a s h i r e w h e r e t h e r e i s a lso lowland peat behind Southport , and bou lde r c l ay and a l luv ium with s o m e lowland peat in Cumber land .

The c e n t r e of the o r ig ina l T r i a s bas in was in the C h e s h i r e P la in a r e a w h e r e the Keupe r M a r l r e a c h e s a t h i c k n e s s of 2500 ft 5 and t h e r e a r e ex tens ive rock sa l t de- pos i t s of c o m m e r c i a l va lue .

5. SOIL, ELEVATION, RAINFALL AND DRAINAGE

The work of the Soil Survey of G r e a t B r i t a i n 17,18 ind ica t e s that the d ra inage of the b rown e a r t h so i l s of the W o r c e s t e r S e r i e s which f o r m s on the Keuper Mar l is g e n e r a l l y good, a l though it is s o m e t i m e s impeded and wate r logg ing may occur at the junc t ion of the soi l p ro f i l e wi th the u n w e a t h e r e d m a t e r i a l .

The heavy n a t u r e of the soi l which f o r m s on the Keuper Marl , and i t s suscep t i - b i l i ty to wet cond i t ions u n d e r high r a i n f a l l s , is ind ica ted by the maps of land c l a s s i - f i ca t ion , lO land u t i l i z a t i on 11 and t y p e s of f a rming . 12 These show that the exposed a r e a of the Keuper M a r l f o r m s a good but gene ra l l y r a t h e r heavy type of land used p r e d o m i n a n t l y as meadow and p e r m a n e n t p a s t u r e fo r da i ry ing , with g r e a t e r or l e s s e r a m o u n t s of a r a b l e a c c o r d i n g to the l o w e r o r high r a in fa l l of the a r e a .

The ou tc rop a s shown on the so l id geology map o c c u r s main ly in p la ins and at m o d e r a t e e l eva t ions , m o r e than o n e - h a l f of it lying below 200 ft and the r e m a i n d e r r a r e l y r i s i n g above 400 ft ( P h y s i c a l MapS). Somewhat m o r e than one-ha l f of this a r e a is c o v e r e d wi th d r i f t d epos i t s (Fig. 1).

The r a i n f a l l (Table 1) i n c r e a s e s f r o m eas t to west , and with i n c r e a s i n g elevat ion. The e a s t and c e n t r a l a r e a s a r e r e l a t i v e l y dry , with 22.5 to 25 in per y e a r , r i s i n g to 25 to 27 .5 in at e l eva t i ons above 200 ft and as high as 30 in above 400 ft . In the n o r t h - w e s t and s o u t h - w e s t r a i n f a l l i s about 30 to 35 in at ave r age e levat ions , and in t h e s e a r e a s work ing wil l be i n t e r r u p t e d m o r e than in the o t h e r s by wet wea the r (Ra in fa l l Map9).

6. CONCLUSIONS

1. The Keupe r M a r l is an anc ien t geo log ica l deposi t of gene ra l ly r e d d i s h - b r o w n m a t e r i a l m a d e up of f ine p a r t i c l e s of qua r t z , c a rbona t e s and c lay m i n e r a l s . It r e - p r e s e n t s an a c c u m u l a t i o n of the e r o s i o n deb r i s of su r round ing mounta ins , which was d e p o s i t e d in a l a r g e in land bas in hav ing i n t e r n a l d r a inage and a hot c l i m a t e in which d r y p e r i o d s a l t e r n a t e d with heavy r a i n s .

2. Mos t of the K eupe r M a r l o u t c r o p s in p la ins and at m o d e r a t e e levat ions , m o r e than ha l f of it below 200 ft . R a i n f a l l v a r i e s f rom as low as 22.5 in per y e a r in the e a s t to o v e r 35 in in the wes t . The so i l f o r m e d on the Keuper Mar l by s u r f a c e w e a t h e r i n g is of ten too heavy fo r a r a b l e use , e spec ia l ly in the a r e a s of high ra infa l l , and is u s e d m a i n l y as meadow and p e r m a n e n t pas tu re .

3. The outcrop cove r s an area of about 5000 square mi les , and has the f o r m of a ~y~, the centra l a rea occupying much of cent ra l England, the a r m s extending to the North Sea and to the I r ish Sea, and the tail to South Wales and the Engl ish Channel. A map has been compiled which shows that drif t depos i t s cover nea r ly all of the nor th -eas te rn and nor th-wes te rn a rms , and about one-hal f of the cen t r a l r eg ion and south-wes tern tail.

4. The Keuper Marl will be encountered in engineering works not only in the a r e a in which it is exposed, but it may also be met with in excavat ions and dur ing p i l e - driving in the overlying drift deposi t s and in the younger over ly ing r o c k s along the eas tern border of the outcrop, but not in the o lder rocks to the wes t of the outcrop .

The engineering p roper t i e s of the Keuper Marl a re r e la ted to i ts m ine ra log i ca l composition and chemical and physical p rope r t i e s . These will be d e s c r i b e d in l a t e r repor ts .

7. REFERENCES

.

.

3 .

.

.

.

.

.

.

10.

11.

Geological map of Great Britain, scale: 1/625, 000. Chessington, Sur rey , 2nd Edition 1957 (Ordnance Survey).

Atlas of Britain, Oxford, 1963 (Oxford Univers i ty P r e s s ) .

CLAYTON, K.M. A map of the dr i f t geology of Grea t Bri ta in and Nor the rn Ireland. Geogr. J., 1963, 129, 75-81.

WILSON, V. Bri t ish regional geology: Eas t Yorksh i r e and L inco lnsh i re . London, 1948 (H.M.Stationery Office).

EDMUNDS, F. H., and K. P. Oakley. Br i t i sh regional geology: Cen t ra l England. London, 1936 (H.M.Stationery Office).

NEVILLE GEORGE, T., and J. Pr ingle . Br i t i sh regional geology: South Wales . London, 1948 (H.M.Stationery Office).

KELLAWAY, G. A., and F. B. A. Welch. Br i t i sh regional geology: B r i s t o l and Gloucester . London, 1948 (H.M.Stationery Office).

Physical map of Great Britain, scale: 1/625, 000. Chessington, 1957 (Ordnance Survey).

Rainfall map of Great Britain, scale: 1/625, 000. Chessington, 1949 (Ordnance Survey).

Land classi f icat ion map of Great Britain, scale: 1/625, 000. Chess ington, Sur rey , 1944 (Ordnance Survey).

Land utilization map of Great Britain, scale: 1/625, 000. Chess ington. 1944 (Ordnance Survey).

12.

13.

14.

15.

16.

17.

18.

Types of f a r m i n g map of Grea t Britain, scale: 1/625, 000. Chessington 1944 (Ordnance Survey).

SHERLOCK, R. L. The P e r m o - T r i a s s i c formations: a world review. London, 1947 (Hutchison ' s Scientific and Technical Publications).

WILLS, L . J . The pa laeogeography of the Midlands. Liverpool, 1950 (Universi ty P r e s s of Liverpool) .

WILLS, L . J . A pa laeogeographica l at las of the Br i t i sh Isles and adjacent par ts of Europe . London, 1952 (Blackie and Son Limited).

WELLS, A. K., and J. F. Kirkaldy. Outline of h is tor ica l geology. London, 1959 (George and Allen Unwin Ltd).

CROMPTON, E., and D. A. Osmond. Memoirs of the Soil Survey of Great Britain: The Soils of the Were District of Shropshire. London, 1954 (H.M.Stationery Office).

AVERY, B. W. M e m o i r s of the Soil Survey of Grea t Britain: The soils of the Glas tonbury d i s t r i c t of Somerse t . London, 1955 (H.M.Stationery Office).

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