E ! P L A N A T O R Y N O T E S
TO AC C OM PAN Y A N EW
G EOL OG IC AL M AP
ENG LAND £5 W ALES
AR H B AL D G E K E D F R S IR C . C . . I I I , S . S
D ir ec to r Gen e r al of t he Geo lo g ic al S u r vey
J OHN BARTHOLOM EW 8: C O.
(t h e E b in b u rg b G e o g raph ic al an s t it u t e
1 897
J H K A IH UNIV E RS ITY OF C AL I FORNIA SANTA BARBARA
E! PLA N ATO RY N OTES
TO AC C OM P A NY TH E
G e o lo g ic a l M a p o f E n g la n d
a n d W a le s
I N C E the appearance in the year 1 8 1 5 of the first general E geological map of ngland and Wales, by William n an d Smith , umerous maps of the whole of parts of the a coun try on various scales have been published. The e rliest
. G of these, by G B . reenough, was begun while that of William a r f —in Smith was in prepar tion , and appea ed our years later
1 8 1 9 . It passed into the hands of the Geological Society of
. London , has from time to time been improved, and is still on sale . Its topography, however, compiled and engraved in the early part of the century, was from the beginning imperfect, a and its geology has been so repeatedly and extensively ltered . that its later forms bear only a general resemblance . to the 1 8 ori inal . The Geological Survey, begun in 3 , has g 5 _ now completed the mapping of the whole country on the scale of ' c e o n On e in h to a m ile, and is issuing a r duction the scale of ' All a re four miles to one inch . general m ps now prepared a
ffi c . In 1 8 l based on the sheets of this o ial survey 59, the ate R Sir A . C . amsay, then Local Director of the Geological a e E n Survey of Great Brit in , publish d a general map of ngla d and Wales on the scale of twelve miles to an inch. It was a reduction from the Survey maps as far as these had at the time u c i ‘ ditio n s has d . s c e ss ve e been publishe In it been improved, ' t h st ee e . be i and up till now it has b n available map , but ts 4 G E O L O G I C A L M A P OF E N G L A N D A N D W A L E S topographical basis was too inaccurate for the production of a wholly satisfactory representation of the geology . a Five years ago, Mr. Bartholomew, who had with great l bour constructed from the she e ts of the Ordnance Survey a general topographical m ap of E ngland and Wales on the scale of ten miles to an inch , expressed to me h is willingness to employ the u c same plates for the prod ction of a geological map of the ountry, if I would supe rintend the reduction from the published maps of the Geological Survey . His map is so good as a general Of topographical representation the country, that it appeared to me likely to prove convenient and useful if the geology were inserted on it . Accordingly, his proposal was eventually carried f into e fect , and the map so prepared is now issued to the public . ’ a While the reduction has been made by Mr . B rtholomew s able assistant , Mr. Bosse, it has been repeatedly revised by some of a my colle gues in the Geological Survey, as well as by myself. a a The late Mr. W . Topley, took l rge share in the early u stages of this labo r, and since his death the task has been carried on by Mr . H . B . Woodward , Mr. W . Gibson , a and Mr . W . W. Watts . I have dr wn the Sections which are place d round the borders O f the m ap to explain the geological structure of the country . The following brief Notes are intended merely for the general reader or traveller who may have no special geological w a kno ledge, but may be induced to t ke the map with him as a convenient guide in !ourneying across the country . The meaning of the various colours and the n ature of the rocks they represent are here briefly explained .
A cursory glance at a geological map of E ngland and Wales reveals some of the fundamental features in the geology of the
. : country I n the first place, it shows that a line drawn in a nearly north and south direction from the coast of Durham“ about the mouth of the Tees, to that of Devon , at the mouth E x e a of the , divides the region into two p rts . To the west of i r i that line the colours are d st ibu ted . n patches Of widely dif
fe ren t . TO sizes, and apparently scattered at random the east,
e . i on th e other hand , the s veral tints are disposed n bands which follow each other continuously across the island from r E the sho es of the North Sea to those of the nglish C hannel . In the western half of the country the rocks belong mostly to ' Th h the Palaeozoic formations. ey ave generally been greatly disturbed, many of them having been plicated , crumpled, and E X P L ANAT O R Y N O T E S 5
a a squeezed . For the most part they consist of harder m teri ls
than those to the east of them . Hence, partly owing to their ' a u rabilit y gre t er d , and partly to the influence of their disturb
e . an cs and upheavals , they rise into the highest tracts of ground n Begin ing on the north , and tracing the series of older rocks e from the Scottish Border to Devonshir , we pass successively
over . the hills of the Lake Country , the Pennine Chain , Wales ,
and Dartmoor, and we note that these eminences usually form a detached groups, such as those of Cumberland, Westmorel nd , W and North ales.
I n the eastern half of the island, on the other hand, the rocks are arranged in successive bands which present their
edges towards the west , and sink below each other towards th e the east. The harder members of series, such as lime
stone and sandstone , rise into long ridges , while the softer clays, marls, and shales subside into valleys or spread out
into plains . The hills are not only less lofty than those of the western side, but they are further distinguished by their prolongation into continuous ridges . The most familiar examples of this type of sc enery are supplied by the chalk hills. Thus the North Downs, which run for many miles
’ c lifls westward from the Dover , mark the trend of the chalk through that part of the country, while the corresponding range of the South Downs reveals the long unbroken outc rop a of the same rock from Beachy Head to Salisbury Pl in . ' It is thus evident that the landscapes of the country depend for their character mainly upon the nature and dis t ribu tio n of the rocks underneath the surface . The traveller or tourist who !ourneys with a geological map in his hand can mark how each distinct ch ange in topography arises from a corresponding alteration in the character of the geology . The variations of scenery consequently acquire for him a n e w mean ing and interest . There is no part of Europe where the relation E here described can be better seen than in England . ven from a rapid railway !ourney much may be learnt here regard e ing the depend nce of topography upon geological structure .
In the second place, a little closer study of the map will O show us that , on the whole , the ldest rocks lie along the western shores, and the youngest along the eastern . If we were to land in Anglesey and traverse the country to the coast of ff Su olk , we should pass successively from some of the most ancient formations of Britain to some of the newest, as is illus
- At t rate d by the section on the left side of the map . Holy 6 G E O L O G I C A L M A P O F E N G L A N D A N D W A L E S head we should find ourselves among quartzites and schists of higher antiquity than even the most ancient of the Palaeozoic n formations , which further south , in Anglesey, are fou d resting C ae rn ar on the edges of these primeval rocks . Crossing into vo n sh ire O , we should come upon some of the ldest st ratified o a a dep sits in the country, belonging to the C mbri n system , an d from these, ranging into the great cone of Snowdon , and a thence into Montgomeryshire, we should sce nd in the geo o f logical scale through the vast thickness the Silurian system , l up to the base of the O d R e d Sandstone . We should next
enter upon the still younger Carboniferous system , and pass in c suc ession into the Permian and Triassic formations, until , in a Leicestershire, we should reach the edge of the J ur ssic series . The various members Of that series would stretc h to north ward e and southward of our line of traverse, the succ ssive limestones rising into long lines of escarpment and sinking gently eastward
- under younger strata, until , beyond the alluvial fen country
of Cambridgeshire and Huntingdon , the Chalk , with its long a a escarpment, would present itself, undul ting e stward through ff Norfolk and Su olk, and slipping gently under the much
younger Crag deposits , wh ich are laid bare by the waves E along the ast Coast . l In the third place, fu rther examination of the map wi l . disclose the important fact that by far the largest part of t he
framework of the country consists of sedimentary rocks, that c is, of deposits of fragmentary or detrital materials whi h have
‘
se a. been laid down under water, and mostly under the The det rittrs largest part of these materials is composed of mechanical ,
' l t h ravels Of ike e g , sands, and muds our present shores and
- flo o r sea , and it now appears solidified into such rocks as
s. sandstones, grits , conglomerates , or shale A considerable
proportion , however, consists of th e remains of once living o calcareous organisms, such as shells, crinoids, and c rals, and
is now found in the form of limestone . The forms of surface produced by the mechanical sediments are well exhibited by an d e the grits, greywackes, slat s of Wales , which have been
greatly plicated and cleaved, and by the horizontal Millstone
' Grit of t he pic t u re squ e dales of Yorkshire. The scenery of
the limestones is typically displayed by the Chalk downs, by
- an d the Mountain limestone uplands of Derbyshire, by the J urassic ridges of the C o tteswo ld Hills and the moors o f
Eastern Yorkshire.
In the fourth place, the map clearly shows that while most E X P LA N AT O R Y N O T E S 7
o e of the country is com p sed of s dimentary materials, it con tains also many detached masses of igneous origin . These are mainly confined to the western side of the island . Some of them are portions of large bodies of eruptive material which a prob bly never reached the surface, but was intruded from below into the crust of the earth and solidified there . The . granite tracts of Devon and Cornwall may be taken as ex
- am ples of this type . But a large proportion of the igneous — rocks are of truly volcanic origin that is , they prove that volcanic action was vigorous where they now occur. They include many varieties of lavas and ashes . As they are inter c alat ed in successive stratified formations, they mark widely separated periods of volcanic activity . The oldest volcanoes of which the geological epoch can be fixed were those which have left their lavas and t u fls or ashes in the Cambrian system of North and South Wales . The most prolonged and ex d tensive eruptions took place in the Silurian perio , and pro du c e d the masses which now form the more conspicuous hills Gl de r of the Lake district, as well as Snowdon , y , the Arans,
Arenig, Cader Idris, and many more heights in Wales . There are no known volcanic rocks in the Old Red Sandstone of England or Wales ; but they occur on a diminished scale in the Devonian system of Devonshire, and in the Carboni ferous series of the Isle of Man , Derbyshire, Somerset, and
Devonshire . The latest English volcanoes appear to have been those which erupted certain dark basic lavas in the Permian period near Exeter and Crediton ; but in Tertiary time some Of the fissures which were then opened in Britain E o stretched across the North of ngland , and gave passage t the uprise of long dykes of dark lava . The most conspicuous of these dykes, that of Cleveland, may be seen on the map ex tending from near the Yorkshire coast to near Carlisle . The accompanying Table represents the succession of the E various geological formations of ngland and Wales, arranged in stratigraphical order, the youngest being placed at the top and the oldest at the bottom . With regard to the Igneous R a a ocks, the three gre t groups of B sic (Serpentine , Basalts,
Dolerites , and Gabbro) , Intermediate (Syenite , Diorite, Ande R F elsite s u artz o r h r sites), and Acid ( hyolites, , Q p p y y, Granite, and Granophyre) , are distinguished on the Map . 8 G E O L O G I C A L M A P O F E N G L AN D A N D W A L E S
T ab l e o f t h e G e o l o g i c al F o rm at i o n s o f E n g lan d n l in s n n r a d W a e s d e c e d i g o rd e .
B an d lown s . fl via ile a m - Re c e n t u t llu viu an d rive r te rrac e s. e a n o w m in in s m e ac e s t h e O d es i n s P t, for g o pl , l t port o sib be n i n i i d pos ly lo g g to th e Glac al Pe r o .
C ave rn d e posits.
S u bm e rge d fore sts. e s u a in n d m a i n d i Re c e n t t r e a r e e pos ts.
Raise d beac h e s .
- k b k i e lsea. Es e m . E at c s S Plateau grave l s. rs Coo e roc rr of
Morain e s of t h e high e r h i ll s.
- e b u d e c a M idd e san ds an d a e s. e Upp r o l r l ys. l g r v l Low r u - a bo ld e r c l y.
. R F es Be d u . E or t gro p V e bo u rn e i d W V y an d C h ll esfor Crags. E R ic a e d an d N C . N orw h r g
. R t E t b d S . e s . E r h D C orallin e or S u ffolk Crag . L e n am Be d s. O L h
H am st e ad g rou p . B m e bridg e grou p . Osb n or e grou p .
H e adon g rou p .
Uppe r B agshot an d B arton grou p . M idd e Ba s an d B rac kle sh am u l g hot gro p . o e Ba u L w r gshot g ro p . n d n a Lo o Cl y. Oldh ave n be d s VV o o lw ic h an d e adin u , R g gro p . an n Th e t S a d .
e a k i fli i Upp r Ch l w t h n ts (S e n on an ) . Midd e C a k i u flin t s u n ian l h l w tho t (T ro ) . Lowe r C halk (C e n om an ian ) e e n san d Upp r G re . au G lt.
e ee n san d e t i S e n c a & c . N e c m an . Low r Gr ( p o l y, , o o ) W a e d e n ee n c a . o m i S & c N e c o an . l ( p to l y, , )
u bec k u P r gro p . an d u Portl gro p . K im e id e u r g gro p . C a ian u or ll gro p . Ox d a n K k for C l y a d e ll aways roc . e a B a O i te u Gr t or th ol gro p . ’ Fu e ll r s Earth . n e i O i te I f r—or ol . i as e Midd e an d e . L Upp r, l , Low r E X P L A N AT O R Y N O T E S 9
M a n e sian im n g L esto e .
Red M a s S an d s n es an d B ec c ias. rl , to , r
- Coal m eas u res. Mi lst n e i l o Gr t.
Carbon ife rou s Lim es ton e se rie s.
0 b N 2 o z a5 i Uppe r. z m M i dd e . S 5: Lu dlow g rou p . . a. k W e n c u . 2 lo gro p O d 5 p Ll an ove ry g rou p . D: n Ba a an d C a ad c u i 5: l r o gro p . 3 Llan d e ilo grou p . 8 Are n ig grou p . O en u s se ies em ad c s a es in u a fla s . U ppe r or l r (Tr o l t , L g l g ) Middle or Paradox id e s se ri e s (M e n e vian ) . Lo we r or Ole n e llu s se rie s ( H arl e c h an d Llan be ris) . 1 — - P RE C AM B RlAN (x) . In various parts of the country cer tain ancient rocks , which rise to the surface in the midst of much - younger formations, may be classed together as pre Cambrian , though they probably represent widely separated periods Of f geological time . O these the largest display is to be found in Anglesey and the western borders of Caernarvonshire . They consist of various gneissic and schistose rocks, including green silky schists, like those of th e Scottish Highlands , and large a . lenticular m sses . of white quartzite The quartzite of Holy h as - head yielded some worm burrows, like those found in the west of Sutherland and Ross . It is difficult to fix the true strati graphical position o f these rocks ; but as they are covered unconformably by unaltered Lower Cambrian strata, they must a be older than the C mbrian period . They evidently consist in great part of extrem ely metamorphosed sedimentary mate rials . They include also various igneous intrusions, while some of the green schists suggest that they may perhaps have been 1 Th e le tte rs an d fig u re s pl ac e d afte r th e n am e s of the syste m s an d for m at i n s e e t o t h e s m b s e m d di i i o r f r y ol ploye to st n g u sh t he m o n t he m ap. A 2 I O G E O L O G I C A L M A P O F E N G L AN D A N D W A L E S ff originally basic volcanic tu s . Some of the more massive parts of the igneous series to the east of Holyhead display in great perfection the proofs of intense mechanical deformation . Cores of the original rock m ay still be recognised amidst the crushed material around them which has been converted into green schist . On the eastern Welsh border, south and east from Shrews a n bury, group of extremely ancient volca ic rocks has been named Uriconian by Dr. Callaway . It forms a ridge on which a O a the Siluri n and even the ldest C mbrian strata rest . Its - rocks are thus shown to be probably pre Cambrian . They c a rh o consist of compact vol anic ashes and felsitic l vas, with y c litic structures , wh i h point to some of the earliest eruptions E a in the geological history of ngl nd and Wales . — Other small masses of pre C ambrian rocks rise to the surface l in the Malvern Hills and at the Lizard Point , while a large - but much obscured tract lies in Charnwood Forest, where a some striking volcanic agglomer tes occur, probably of pre Cambrian age . The occurrence of these detached areas of rocks that can claim so high an antiquity Opens up some interesting and difficult questions in the geological evolution of t h e c ountry . Where they appear from under the Cambrian strata they were prob ably deeply buried beneath that system but there would appear to have been some great terrestrial a a movements during Pal eozoic time, whereby cert in portions of - a a an d the pre Cambri n pl tform were ridged up, also enormous e denudation , by which these tracts had the whol of their over ' o f m e o fl lying pile sedi ent stripp d them . The Uriconian ridge a t Th e was exposed and buried ag in in Upper Silurian ime . roc ks of C harnwood Forest survived as a picturesque group of peaks un til they were entombed under the marls of the Triassic e waters . It is evid nt that th e local disturbances during the Palaeozoic periods must have been on a great scale, and that while sedimentation went on with little interruption in certain ’ far Ofl districts, it was interrupted by upheaval in others not , a u and gave pl ce to st pendous and prolonged denudation . The thick mass of sedimentary strata forming the tract of country known as the Lo n gm yn d was regarded by the G e o lo gic al Survey many years ago as of Cambri an age ; but more rec ent investigation tends to pl ace it below the Cambrian system , and above the Uriconian volcanic series . A A a — C M B RI N ( ) . This great system of rocks occupies a a a c omparatively small space at the surf ce . It ppears in E X P LAN AT O RY N O T ‘E S I I - Anglesey , in Caernarvonshire and south west Pembrokeshire, emerging from underneath the overlying c o n fo rm able ‘ S ilu rian strata . It is seen also in a small tract at the Malvern Hills , i . i n Shropsh re, and in Warwickshire Probably a large part of the Skiddaw Slates, which cover much of the northern part of the Lake District , and reappear in the Isle of Man , is to be referred to this ancient division of the geological record . The Cambrian system consists mainly of mechanical sedi ments, which in the lower part are somewhat coarse in texture, r forming g its and conglomerates, but which pass upward into fi ner sandstones and shales or slates . It is usually grouped in three divisions , each distinguished by a characteristic form of trilobite . The lowest or Olenellus series has been determined h e by Professor Lapworth to occur in t Shropshire area, where o it c nsists of thin quartzite passing up into flags, grits , shales , an d and sandstones , where it has yielded the characteristic Gla ze/h a . In that region it is overlain with conglomerates P ar ado x ides and limestones containing , forming the M iddle C . hin t ambrian group The Upper group , composed of the S e o n ' ' fl rde d len u s D z 'o ra f u s a o O e & c . shales , has specimens of , b g p , The total thickness of these three groups in the Shropshire 0 0 0 region is estimated at about 3 feet . In Wales,however, a the system att ins considerably greater dimensions, reaching perhaps to feet or more . The Lower group in the , c o n lo m e Principality consists of massive sandstone grits, and g rates (Harlech , Llanberis) , which lie upon and pass down into ' t u fls a volcanic platform , consisting of , diabases, and quartz i i felsites Peb d an of Dr. Hicks) . The Middle or Menevian group is well developed in South Wales , where along the coast of Pembrokeshire its sandstones , shales, and slates, about 60 0 c feet thick , have furnished a number of fossils, in luding , the a e typical P ar do x id s. The Upper group consists of two divi n t he sions . At the bottom , and passing down i to Menevian — F a strata, lie the Lingula lags bluish and black slates and fl gs, whi c h took their name from the abundance of a lingula (Lin ar g alella D avin !) in them . They e believed to sometimes 0 0 0 c . a exceed 5 feet in thi kness The Tremadoc sl tes , well e develop d in the district from which they take their name, and 1 0 0 0 a where they are about feet thick, contain number of a Olen u s trilobites, mong which the characteristic oc curs . The top of the Cambrian system of Wales is now generally drawn u at the summit of the Tremadoc group, but there is no abr pt 1 2 G E O L O G I C A L M A P O F E N G L AN D AN D W A L E S break at this horizon , the Cambrian sediments passing gradu w ' ally up ard into the Silurian series . N — S ILURIA (b) . This system occupies a large part of n Wales. Sinking u derneath younger formations, it rises again e to th e surfac farther east, and appears in a number of de tac h e d areas from the head of the estuary of the Severn north W wards through Gloucestershire, Herefordshire, orcestershire, ' and S taflo rdshire ; but it no doubt extends under the Old R e d Sandstone and C arboniferous rocks across the whole of the h E Nort of ngland , for it ascends once more to the surface in Westmoreland and Cumberland, where it forms the hilly ' It rea ears ground of the Lake District. pp in the Isle of Man, and extends under the Irish Sea into Ireland on the west, and into Scotland on the north . The Silurian rocks of England and Wales are divided into an d two portions, Lower Upper, each of these being further e grouped into separat formations , distinguished from each a other partly by lithologic l characters , but chiefly by their i n a typical organic rema ns . O e distinguishing fe ture of these G e n fo lder formations is the presence in them of abundant / , which vary both in genera an d species from bottom to top of are the system . Double graptolites specially found in the a Lower Silurian deposits, and single gr ptolites in the Upper. w The hole system has been arranged in zones , each marked by the presence of some distinctive graptolite . Trilobites are u likewise abundant , and may be made use of to disting ish the several formations . L o wer S ilu rian a —4 I . The form tions are three in num ber a Arenig, Llandeilo, and Bala or Car doc . l The Arenig formation (b ) may reach a thickness of 40 0 0 a feet . It consists of dark shales, slates, fl gs , and sandstones, which are typically developed in and around Arenig Mountain . A prominent feature of this division of the system is the occur a o rence of bundant intercalated volcanic r cks, which prove that while the Arenig sediments were deposited there were active submarine volcanoes over the site of what is now the ' u s heart of Wales . The lavas and t fl of these eruptions rise o e int conspicuous eminences, such as Ar nig Mountain; the C . Arans, ader Idris, and others 2 Th e b 0 0 0 Llandeilo formation ( ) , sometimes perhaps 3 feet thick, comprises dark argillaceous, sometimes calcareous fla st o n s g e , sandstones , and shales, and was first named by E X P L AN AT O R Y - N O T E S 1 3 el Ll n o aermar Murchison, from its dev opment about a deil in C t he n shir e e . It extends into Pembrokeshire, and ris s to the f sur ace in the Lower Silurian inlier of Builth . The Bala or Caradoc rocks (b3) have been computed f 60 0 to reach a thickness O 0 feet where fully developed . In North Wales they consist of grey and dark slates, grits, and sandstones, with two subordinate seams of limestone, and a att in a great development around Bala, in Merionethshire, e where th y were first studied by Sedgwick . In that region they include a vast mass of contemporaneously erupte’d vol c an ic rocks which tower into some of the finest scenery of ‘ North Wales . Snowdon and the surrou nding mountains con sist largely of thes e volca nic m aterials . ‘ a r In the district of C e Caradoc, Shropsh ire, the corre s n in po d g strata consist of yellowish and grey sandstones . In an the Lake District enormous mass of volcanic material, estimated by some observers at or feet in thick ness , occupies the place of the Bala and Llandeilo rocks below a limestone (Coniston) , which from its fossils is regarded l as the equivalent of the Bala limestone of Wa es . r l a I I . The Uppe S i u ri n formations are likewise three in — c w number Llandovery , Wenlo k , and Ludlo . 5 ( L ) The Llandovery rocks (b ) consist of a lower group of “ 60 0 1 0 0 grey grits, from to 5 feet thick a central group of yellow and ‘ brown ferruginous sandstones (May Hill sand 8 0 0 stone) , about feet thick , resting unconform ably on the Older members of the system ; and an upper group of fine ‘ Taran n o n smooth grey or blue shales ( shale) , having an extreme Of 1 0 0 0 1 0 0 thickness to 5 feet . The central division of the Upper Silurian series or Wen bc lock group ( ) , in the typical Silurian district of M urchison , — cons ists of three distinct groups of strata a lower limestone h O f and s ale (Woolhope) , well displayed in the valley Woolhope , 0 0 Herefordshire, where it is about 3 or 4 feet in th ickness ; a a c t centr l mass of grey and bla k shales (Wenlock Shale) , race able for ninety miles from the Severn near C oalbro okdale to r c i Caerma then , and in the northern part of its ourse atta ning a depth of more than 20 0 0 feet ; and an upper calcareous — a - deposit, known as the Wenlock Limestone thick bedded, fla c 1 0 0 0 0 k ggy, and oncretionary rock, from to 3 feet thic , a and abounding in fossils, particul rly in corals . In North Wales the soft shales and limestones of the Wenlock group l o a e an d give p ace t h rd grits, flags, sandstones, m u dston s , I 4 G E O L O G I C A L M A P O F E N G L AN D A N D W A L E S shales (Denbighshire Grits), which sometimes reach a united 0 0 0 thickness of at least 3 feet . N The Ludlow group ( ) , in the typical district of Siluria, is essentially composed of shales , with occasionally a central ban d ~ o f a r limestone (Aymestry) , the whole having an gg e o f 1 0 0 0 gate thickness about feet . The highest member of a the group consists of a b nd of fine yellow, red, and grey ac tile sto n e s m ic eous sandstones ( ) , which form a passage into ld Red the overlying O Sandstone . These rocks are best seen in the Herefordshire region , where they were studied by Murchison . The remarkable change into hard, cleaved, and plicated rocks which is observable when the Upper Silurian formations o bserv are followed , even into North Wales, continues to be able northwards across the Lake District into the south of Scotland. Nevertheless the stratigraphical position of the northern Silurian formations is satisfactorily fixed by the occur rence of marked zones of graptolites . The Upper Silurian formations are developed in the eastern and northern tracts of Wales and in the southern part of the hills of the Lake District . — n O LD RED S ANDS TO N E AND DEV O NIAN (c ) . Alo g the eastern border of Wales the highest member of the Upper Silurian series passes upward conformably into the red strata — which form the base of the Old Re d Sandstone a vast m succession of red rocks which , stretching fro Shropshire Of across South Wales, attains a thickness probably not less than feet . The lower parts of this system of red sedi Of fla st o n s ments consist red and green shales and g e , with sandstones and thin cornstones . The central and main por tion is made up of red and green sandy marls and clays, with red sandstones and cornstones, the higher members consisting of grey, red, brown , and yellow sandstones, and bands of conglomerate, pass upward conformably into the base of the e Old R e d C arboniferous system . In g neral the Sandstone of En a gland and Wales is barren of org nic remains . Its lower and central parts have yielded remains of fossil fishes ( C epha l ' ’ as zs P ter as zs p , p , while the higher portions have furnished ’ ot her genera of fishes H o loptye/zzu s) and remains - of land plants . In North Wales and the northern counties of England the narrow belts and patches of Old R ed Sandstone which appear E X P L A N ATO R Y N O T E S 1 5 between the Silurian and Carboniferous formations belong to the Upper division of the system . They pass upward into the u n c o n Carboniferous strata above them , and lie with a violent formability on the Silurian rocks below. In these regions, therefore, a large part of the stratigraphical series is wanting, which is S upplied in South Wales and Shropshire . The Devonian system in England is confined to Devon n and Cornwall . Though it presents a strong co trast to the ld R d l alaeo n t o O e Sandstone, both in its lithologica and its p logical characters, it is regarded as the geological equivalent of ld R e d - ac that system . The O Sandstone appears to have cumulated in a series of lakes or inland seas . The Devonian h formations, on the other and, are shown by their included r fossils to have been deposited in the sea . They are gene ally grouped in three sections, named Lower, Middle, and Upper. r The Lower Devonian g oup consists of slates, grits , and greywackes, seen at Cockington and elsewhere near Torquay, and at Foreland and Lynton in North Devon . The Middle group is best displayed in South Devon , where it consists largely of massive fossiliferous limestones (Torquay, Plymouth) , which pass laterally into volcanic rocks (Ashprington) . In North Devon this group is represented by the grey silvery l slates of Ilfracombe, and the limestone grit and s ate of Combe Martin . The Upper Devonian rocks consist of red and grey slates and grits sometimes with a fossiliferous limestone (Chud - leigh . These so ) _ strata pass upward into the called Culm measures, which belong to the Carboniferous system. The chief horizons for Devonian fossils are to be found in the limestones of Torquay and Plymouth , which have furnished a large series of corals, together with trilobites and brachiopods . C ARBONIF EROUS —This important geological system x is e tensively developed in Englan d and Wales . It forms a o broad tract of country , extending from the b rders of Scotland southward through the Pennine C hain till it sinks below the plain of the Midlands at Derby . In a broken fringe it encircles Wales, from Anglesey to the mouth of the Dee , and thence southward into Monmouthshire, where it spreads out into the a - fie ld high tablel nd of the South Wales coal , and stretches to the western shores of Pembrokesh ire . It rises in a numbe r of - E detached tracts in the centre and south west of ngland, and covers a wide space in Devon and Cornwall . It is divided into three m ain series of strata, each of which is distinguished 1 6 E O ‘ M O F E N G O L G I C A L A P . N G L A N D A D W A L E S ma —4 r M ills o n e ‘ G rit on the p Ca boniferous Limestone, t , and u Coal meas res . 1 3 1 . r d ( The Ca boniferous Limestone ( , formerly known as the Mountain Limestone) forms conspicuous topographical ' art s o f features in some p the country where it is well developed . su rro u n ds th - fi ld It e South Wales coal e , where it passes down R into the Old e d Sandstone . In the Pennine Chain it attains 0 its 0 0 o t . the great thickness of 4 feet , yet base is n there seen o u t Spreading over the high grounds of Derbyshire, Yorkshire, and Lancashire, its gently inclined undulating strata form a i i i str king type of scenery, pro!ecting to the surface r sheets and an d knobs of bare pale stone, winding in white escarpments E t along the green slopes of the valleys . ven where i does not spread so continuously over the ground, it sometimes reaches a , great development, as in the ridge of the Mendip Hills , 0 0 0 o f - where it is 3 feet thick . It consists massive, well bedded r m in s f limestone , composed of the e a o calcareous organisms . ’ Its fossils may often be seen pro!ecting in en o rmous numbers a from exposed surf ces of the rock, where they have been d etched out by the weather. Traced northwar the limestone is found to be more an d more split up with intercalations of shale and sandstone, which contain land plants . We may infer r f that, while a tole ably deep sea extended over the south O E o o ngland , a land cl thed with vegetation lay somewhere t the north , probably where the Scottish Highlands now rise, and ' t errestrial su rfac e d that from this the sand, mud, and rifted ‘ plants were derived . Some remnants of submarine volcanoes ‘ r ' occur in the Ca boniferous Limestone of Derbyshire, where a series of basic lavas an d tuffs (toadstone) is associated w ith l necks of agglomerate. At the south end of the Isle of Man , - - - near Weston super Mare, and in the Culm measures of Devon shire, other volcanic intercalations have been found . The Millstone Grit (d4) comprises a persistent group of s grit and sandstones, with shales and clays , which overlie and pass down into the limestone series below, and shade - a upward into the coal bearing series above . These str ta 0 0 1 0 0 0 are from 4 to feet thick in South Wales, but in ' North S tafi o rdshire they have been estimated to be 40 0 0 and in Lancashire 550 0 feet in thickness . In Yorkshire arid Lancashire, where they are nearly flat, their successive beds wind along the sides of the dales as long ' regular lines of terrace . “ 5 The C Oal- measu res (d ) are made u p of frequent altern a 1 8 G E O L O G I C A L M AP O F E N G L A N D A N D W A L E S r 0 0 0 land each a thickness of 3 feet. In Devonshire these stratainclude the traces of some contemporaneous volcanoes in the form of thin sheets of lava . To the same period of eruption may possibly belong the various basic sills wh ich in the Midlands and on the Welsh border h ave been intruded a - into the Co l measures . ff The eastern type is quite di erent, and resembles that of Germany . It displays a mass of Magnesian Limestone or dolo M e 60 0 mite ( ) , about feet thick , underlain by some red and a varieg ted sandstones, hard brown shale (Marl Slate) , and thin n limesto es, and overlain by a thin group of sandstones, clays , o r and gypsum , or anhydrite . There is a general dearth of ganie remains in the Permian rocks . The Magnesian Lime stone is the chief fossiliferous repository. This formation is - n e m o u t h best seen along the coast line south of Ty , where it f forms a range of picturesque cli fs . T S S C - At RIA I (f ) . the base of the great series of Second ary or Mesozoic formations lies the Trias, which , consisting, a e like the Permi n , mainly of red strata, was formerly class d R e d with that system as the New Sandstone . It occupies a a tolerably continuous rea, which, beginning near Gloucester, S preads over the great plain of the Midlands , and then divides into two arms , one of which stretches up the west side of the Pennine Chain to Morecambe Bay, while the other sweeps along the eastern base of that ridge to the sea at the mouth - e of the Tees . A detached area lies in the north w st of Cum berland, extending to the shores of the Solway Firth and crossing into Scotland. Another series of patches extends from the head of the Severn estuary across to the southern coast of Devonshire. The Trias consists of three divisions Lower or Bunter ; 2 R a c ( ) Upper or Keuper ; and (3) h eti . The Bunter series (f 1 ' 3) is made up of three groups of 1 0 0 0 20 0 0 strata, having a united thickness of to feet . At - a d the bottom lie soft bright red and variegated s n stones, from I 8 0 to 650 feet thi c k . n the centre a group of harder reddish a a 60 brown pebbly s ndstones and conglomer tes, from to more 1 0 0 0 . than feet in thickness, is known as the Pebble beds While at the top another series of bright - red and mottled 20 0 0 0 sandstones reaches a depth of from to 7 feet. The Keuper series (f 5'6) is composed of a lower group - of red , white, and brown sandstones and marls (water stones) , E X P L A N AT O R Y N O T E S 1 9 from 1 50 to 250 feet thick (f and of an upper group of red and grey shales and marls (f which form the most important member of the Trias . They range in thickness from 8 0 0 to 0 0 0 a sometimes as much as 3 feet , and are particul rly distin - gu ish ed by including beds of rock salt and gypsum . The salt works of Cheshire derive their supplies of brine from this group . R a f The h etic formation ( g , Penarth Beds) is made up a of red , green , and grey marls, black sh les , and pale limestone White Li as which are often only a few yards and rarely reach 1 50 feet in thickness . Yet in spite of its insignificant proportions th is group of strata runs with singular persistence n e throughout England and Wales . O of its most interesting — seams is the bone - bed a ferruginous and micaceous sand a f a stone containing rem ins O fishes and sauri ns . — J URAS S lC (g) . Under this name are comprised the various a strata which led William Smith , in the neighbourhood of B th , to the discovery that the sedimentary rocks of England co u ld be identified from one district to another by means of their - enclosed organic remains . The sub divisions made by him a are still on th e whole ret ined , together with the local provincial names which he attached to them . Four chief divisions are e recognisable, ach of these being separated into minor groups . They range across England from the coast- line of Yorkshire c to that of Dorset, and form some of the most haracteristic scenery of th e country . I n the north they rise to heights of 1 0 0 more than 4 feet above the sea, and form th e broad moor lands south of M iddlesborough . They mount also in the south into the range of the C o tte sw o ld Hills . But throughout most of their course they form a succ ession of low ridges and inter n in t h e ve g plains , former marking the outcrop of the limestones a a and other h rder members of the series , while the l tter indi an a cate the position of the softer shales d cl ys . a m At the bottom of the whole series lies the Li s (g ) , which is composed of three tolerably well- marked groups of Lias 1 strata. The lowest of these, known as the Lower (g ) , consists of numerous thin blue and brown limeston e s with a a O f partings of dark sh le, h ving a total maximum thickness 2 I c 0 0 . n 9 feet the entre comes the Marlstone (g ) , or Middle 0 c e Lias (35 feet) , omposed of various limeston s with under a lying s nds and clays , and sometimes, as in the Midlands and a . a in Yorkshire, including v luable ironstones The Upper Li s 3’ 4 0 0 c a a (g , 4 feet) is made up of shales and l ys , with nodul r 20 G E O L O G I C A L M A P O F E N G LA N D AN D W A L E S n limestones passing up into sa ds . Numerous palaeontological a zones have been recognised in the Li s, each of which has rec eived a name from the c haracteristic ammonite whi c h it con tains . Ten such zones have been separated in the Lower Lias . The Lower Oolites . This series contains three chief 5 - O 260 e sub divisions . At the bottom the Inferior olite (g , fe t) , - in the south western and central counties, consists mainly of shelly (marine) limestones with clays and sandstones , but as it l - an d is fo lowed northward , increasing evidence of fresh water terrestrial conditions are traceable, until in Yorkshire t he strata, 8 0 0 swelling out to a thickness of feet, are composed chiefly of sandstones, together with shales and seams of coal and iron in a stone . Next order comes the argill ceous deposit known ’ E n as the Fuller s arth , which is only found in the souther and - south western counties, where it attains a thickness of nearly 1 0 t h e 5 feet. The uppermost group of Lower Oolites is well a c developed around B th , whence it has been alled Bathonian I n G loucestershire and Oxfordshire it displays three - a - sub groups of strat , of which the lowest consists of th in bedded S t o n esfi eld a limestones and sands ( sl te) , the middle of shelly O limestones (Great olite) , and the uppermost of clays (Brad ford clay) , shelly limestone (Forest marble) , and earthy lime - . Of stone (Cornbrash) these sub groups, the most persistent 9 V is the Cornbrash (g ), at the top of the whole . arying from 0 c 5 to 4 feet in thickness, this rock extends ontinuously into Yorkshire . 10 11 The Middle or Oxford Oolite s (g ) c omprise two - c well marked formations. The lower of these consists of a lo al calcareous sandstone (Kellaways R ock) and of a stiff blue O e and brown clay, well developed in xfordshire, wh nce it has m I a received the name of Oxford C lay (g ) . t r nges from 30 0 60 0 C a a to feet in thickness . The Upper or or lli n group “ 2 0 e c c a (g , 5 f et) onsists of limestone and cal reous grits, with c a c a c o casion l lays , traceable with local modific tions a ross the country from the coast of Dorset to that of Yorkshire . It received its name from the abu n dance of corals in its rubbly a limestone (Coral R g) . The Upper 0 1 Portland Oolites (g are divisible C a into three groups . At th e bottom comes the Kimeridge l y m 60 0 (g , feet) , well developed on the Dorsetshire coast, whence it can be followed into Yorkshire . In the centre lie the Port m c land Beds (g ) , onsisting of marls and sands towards the - base and limestones above, one of which is the well known E X P L A N A T O R Y N O T E S 2 1 Portland Stone, so largely used as a building material . “ u 0 The highest group (P rbeck Beds, g , 35 feet) is best seen o f - in the Isle of Purbeck, where it consists chiefly , fresh water o limestones and clays , including layers of s il with the stumps t h e of the trees which grew in them , but central part of the group contains marine shells. These strata have long been celebrated for the mammalian remains which they have yielded . — C RETAC EOUS This system of formations occupies - d fin E a a well e e d area in the south and east of ngland . C p ping the hills of e astern D evonshire it stretches eastward to the coasts of Sussex and Kent. From this southern band it n diverges at the broad tract of Salisbury Plain, and conti ues - in another band north eastwards to the shores of Norfolk . Beyond the Wash it reappears in Lincolnshire, crosses the O f Humber, and stretching northward into the Wolds York ff - f lam r u h o bo o . shire, is finally cut in the sea cli fs of F g Head The Cretaceous system is divided into two main sections, the Lower or Neocomian and the Upper. The Lower Cre E tac eo u s rocks present two distinct types in ngland . In the southern counties they consist of a lower delta- formation known as the Wealden , surmounted by some marine sandy 2 strata termed the Lower Greensand (h ) . The Wealden group has at its base the Hastings sands and clays (h) , which pass c down into the Purbe k group . Above these comes the thick l h 1 0 0 0 deposit of Weald Clay ( , feet) which forms a conspicuous - E feature in the geological map of the south east of ngland. It represents the delta of an ancient river, and, like modern -d a delta eposits , contains the remains of l nd plants and of terrestrial animals (in this case dein o sau rian reptiles),together “ ! - Y with fresh water shells . I n orkshire the Speeton Clay i ar consists of marine clays and shales , wh ch in their lower p t t E are equivalents of the Kimeridge Clay of the sou h of ngland, but which in their higher parts contain true Neocomian or t h e f -t Lower Cretaceous fossils , while at the top y may even belong to the higher division of the Cretaceous system. The Upper Cretaceous series is divisible into three well marked groups of strata , distinguished from each other alike by lithological characters and fossil contents . The lowest 3 h 1 0 0 0 0 ff group ( ) is known as the Gault ( to 3 feet) , a sti ’ - dark blue clay, with thin seams of pyritous and phosphatic nodules an d occasional seams of gree n sand. This deposit 22 G E O L O G I C A L M A P O F E N G L A N D A N D W A L E S passes upward into certain sandy strata , often greenish in h4 colour, which have long been called Upper Greensand ( ) . a a Under th is term , however, h ve been included strat now - known to be equivalent to the Gault . The Upper group of the system is composed m ainly of the soft pulverulent lime h5 stone called Chalk ( ) , and forms topographically by far the most conspicuo us member of the whole system to which it e gave its name. It is this formation which ris s into the undu c a lating area of Salisbury Plain , and stretches then e eastw rd th into the bare, smooth , treeless ranges of e North and South a Downs, and which reappe rs with the same kind of features in the Wolds of Yorkshire . The Chalk can be separated into — three divisions Lower (Cenomanian) , consisting of the Glau c o n itic Marl, Chalk Marl , and Grey Chalk Middle (Turonian), flin ts composed of white chalk without and Upper (Senonian) , also made of white chalk, but distinguished by the abundance fli of its black n t s. The Cretaceous system of England has undergone consider able disturbance in the southern counties, having been thrown into a series of undulations which greatly affec t its distribution e at the surface . Thus, as illustrated in the horizontal s ctions on the map, the North and South Downs form the two sides of C a broad arch , from the crown of which the halk has been entirely removed so as to reveal the Lower Cretaceous series a in i n the broad pl ain of the We ld . The denudation thus dic at ed is likewise conspicuous along the western outcrop . The fringe of detached patches of C halk on that line are remnants of a once c ontinuous sheet of Chalk th at f ormerly stretched far to the west of the present limits of the formation . The TE RT IARY form ations of England are almost entirely - confined to the south eastern counties , where they occupy two c n e large distri ts . O of these, known as the London basin , e - cov rs a wedge shaped area, which , beginning in Wiltshire, broadens out towards the east, keeping along the base of the North Downs to within a few miles from the North Foreland , ’ - S u fl lk and stretching north eastward to the coast of o . The an m a ot her d uch less extensive district, called the H mpshire basin , is separated from that of London by a broad uprise of the Chalk . Originally the Tertiary deposits were probably - continuous across the whole of the south east of the country. They have participated in the plications which have folded the Cretaceous system and in the subsequent denudation . The E X P L A N AT O R Y N O T E S 23 ‘ extent to which they have been wasted is impressive lyi n dic ate d by the nu m erous outliers scattered over the surface of the Chalk . The E nglish Tertiary formations have been divided into three — E c O . groups o ene, ligocene, and Pliocene EOC ENE The group as developed in the London basin , diff ers in some degree from the type which it assumes in a a Hampshire . At its base lies the Th net S nd , not found in a H mpshire, and best seen in the eastern part of the London . m e basin Next co es a variabl series of plastic clay , loam , sand , - an d R and pebble beds , called the Woolwich eading , and the Oldh ave n Beds succeeded by the chief member of the 3 E — C a i f an d ocene group the London l y ( ) , a sti f brown bluish m E grey clay, with septaria of earthy li estone, which in ssex a 0 0 . ttains a thickness of about 5 feet This deposit is , in the m London basin , surmounted by the Bagshot Sands,but in Ha p ' shire an d the Isle of Wight by a difle re n t and much thicker succession of deposits the most interesting of which are B rac kle sh am the Beds of the Sussex coast, long noted for the E abundance of their marine organisms . The highest ocene strata in the London basin are the Uppermost Bagshot Sands B but in Hampshire they consist of clay ( arton) , which on the an 0 0 an d a coast d in the Isle of Wight is 3 feet thick, is rem rk able for the gre at number and excellent preservation of its a shells . The. B rton Clay is overlain by from 1 40 to 20 0 feet l - m of pure siliceous sand, used for g ass aking, which passes upward into the base of the Oligocene series. The O LIGOC EN E strata of England Occur onlyin the Isle of W ight and part of the opposite c ounty of Hamp . R c E c shire esting onformably on the o ene series, they consist m m a of thin sea s of sand, clay, marl, and limestone , which yreach 0 0 are d a maximum thickness of 8 feet . They divi ed into four f groups , each o whic h is named from the locality in the Isle of a . l t he Wight where it is typic lly exhibited The lowest, ca led c r - Headon group, onsists of two se ies of fresh water deposits, ' a brac kish wat e r . separated by a middle stage, cont ining and w u marine fossils . The Osborne Beds are like ise f ll of fresh water shells . The Bembridge . group consists of two stages, e the lower composed of lim stone, containing abundant land ' - t h e u e r and fresh water shells, pp presenting a thicker succes a -W sion of m rls, of fresh ater, estuarine, and marine origin . - The Hamstead Beds were chiefly deposited in fresh water, 24 G E O L O G I C A L M A P O F E N G L A N D A N D W A L E S estuarine, or lagoon conditions, but their uppermost visible c . h as strata were ac umulated in the sea Denudation , however, removed all the deposits which m ay originally have covered E these strata, and nothing has been left anywhere in ngland to enable us to fill in the gap thus made in the geological record . P Ll C ENE Next in order of age come the O formations, there being no representative in England of the Miocene series . E t The nglish Pliocene is separable in o two divisions, called O lder l . O k and Newer The lder series ( ) comprises the White , Suf o r folk , Coralline Crag, which covers a considerable space in ff the east of Su olk , where it consists of shelly sands, containing 60 . On about per cent . of still living shells the southern edge t he of North Downs , near Lenham in Kent, patches of sand , which lie on the Chalk and descend into pipes in that rock , contain such an assemblage of shells as to prove them to be . a e of Pliocene age Fr gmentary though th y are, they possess as much interest, inasmuch they point to the submergence of the south - east of England during older Pliocene tim e to the 8 6 extent of perhaps 0 feet below its present level . ! The newer Pliocene groups (k ) include the Re d and Nor a ff wich Crag, speci lly developed in Norfolk and Su olk , and consisting of red and brown shelly sands and gravels , in which the proportion of extinct shells is about sixteen , the Chilles an d ford Beds the Forest Bed group. The fossils preserved in these deposits indicate a gradual lowering of the climate of Britain during Newer Pliocene time . Arctic species of shells R e d begin to make their appearance in the Crag, and Medi terranean forms rapidly diminish from the Coralline C rag upwards . The Forest Bed group contains a flora that indicates a mild and moist climate but immediately above it lie layers c of sand, loam , and gravel, with marine Arcti shells and a - c - fresh water deposit ontaining mosses, dwarf willows, and . u birches, and pointing to a temperat re as severe as that of the North Cape . Above the Plioc ene,and covering a far more extensive pro E c portion of the surface of ngland and Wales, ome the various — - a kinds of Drift boulder clays, gravels, s nds, moraines, and other detrital accumulations which record the passage of the a Ic e Age . These superfici l deposits are not shown upon the map , because to insert them would in large measure obscure l the under ying geology of the country . In some districts, as, 26 G E O L O G 1 C A L M A P O F E N G L AN D A N D W A L E S the Section by the two faults which let down the wedge of Wenlock and Ludlow strata between the Lo n gm yn d an d the Uriconian rocks of Hope Bowdler or C aer Caradoc . From this part of the Section an ascending succession of ' strata c an be followed through the Upper Silurian formations o ld Re d c int the O Sandstone, whi h is seen to undulate for n Titt e rs o n many miles to the east. O B rown Clee and t e Hills outliers of Coal - measures have been preserved under intrusive sheets of basalt, and a larger tract of the same formation , - fi e ld spreading out into the Forest of Wyre Coal , lies on the Old Re d Sandstone and extends to the vale of the Severn near Worcester . Here the Section enters the Mesozoic series of strata . First come the Keuper and Bunter groups , fol R a c lowed by the thin band of the h etic deposits, whi h crops out to the east of Worcester and dips under the Lias. Their gentle inclinations enable the strata to spread out over wide areas . Outliers of the Lower Oolites are seen capping the Lias . many miles in advance of the main outcrop Of these groups . Th e members of the J urassic series are successively t h e - traversed , until to south east of Oxford, the Cretaceous system sets in with its prominent escarpment of Chalk rising above the Gault and Upper Greensand . The London Ter t iary basin is shown by the descent of the Chalk below the Tertiary deposits on the one side and its uprise from beneath ° ‘ h n . t em o the other The angle of inclination , however, is so r gentle that, if drawn on a t ue scale, the strata would seem to ’ be nearly horizontal . On the south side of the basin the Chalk mounts into the ridge of the North Downs, and presents another bold escarpment to the great plain of the Weald, where the Wealden groups are exposed in a broad anticline . The ridge of the South Downs is formed by the outcrop of the C halk on d the south limb of the fol . There cannot be any doubt that c t h e a the Chalk was once ontinuous across We ld , and that its disappearance is entirely owing to prolonged denudation . S e tio n ac r o ss tlze c en tr e o E n lan d r o m fi re bo r ders I I . c f g f ' ' a n az /z er tn e C lzeslzzr e P lain s t/ze D er b sn zr e of W a les t D e g o v , y ' ' ' ’ f l c lls an a tlce lain s o tlze Tr en t to tire c o ast o L zn c o ln slzc r e , p f , f —At e at S alqleet . the west end of this S ction the Denbighshire u n c o n grits . o f the Upper Silurian series are seen to be formably covered by the Upper Old R ed Sandstone and Carboniferous . Limestone, against which the . Trias of th e h e vale of . C lwyd i s let down by faults on either side of t ’ n n e depressio . O the east side the three mem b rs of the E X P L A N AT O R Y N OT E S 27 Carboniferous system are seen to dip away from the Silurian a ridge under th e Triassic pl ins of Cheshire, which stretch eastwards to the base of the broad Pennine Chain . The great denudation of the Carboniferous rocks is shown by the outliers of Millstone Grit and Coal- measures left detached - s E on the hill top . ast of Buxton the Carboniferous Lime a stone appears, with its b nds of volcanic toadstone , and after undulating for some miles finally slips below the Yorkshire - fi ld coal e . Still farther east the Permian series dips under the Triassic groups, which occupy the low plain of the Trent, until they pass under the J urassic series . From the fine escarpment at Lincol n that series sinks gently eastward under neath the Cretaceous system , which extends to the coast. S ec tio n ro m t/ze S o lw a ac r o ss tire L ake D ist ric t an d I I I. f y tire P en n in e C lzain t o tire c o ast of Yo r kslt ire at F la mbo r o u g /z — !l ead This Section explains the structure of the ground in the nort h of England . At the west end the Trias rises from under the Solway Firth , and is faulted against the Whitehaven - l coal fi e d, which in turn has been let down by a dislocation m m on the east side . Fro under the unconfor able Car r a bo n ife o u s strat , the Lower Silurian volcanic rocks are seen to emerge, and to be followed by the great mass of Skiddaw slate , with its intrusive granite . After various folds and - fractures the rocks roll over to the south east, and the volcanic series again makes its appearance, and swelling out c c to its maximum thickness , o upies the high grounds of the Lake District, until it dips below the Coniston or Bala Lime stone . Then come the Upper Silurian formations, which extend e astwards for many miles as the platform on which the Carboniferous system there reposes . The Section affords an illustration of the great denudation of that system , Ingle borough and Pe n ygen t remaining as colossal monuments of the amount of material removed . It will be seen that some of the valleys have been excavated completely through the thick Carboniferous series, and have laid bare the Silurian R platform below. Towards ipon , the Permian band sets in , and is soon overspread by the Trias of the plain of the c Ouse, whi h in turn dips under the J urassic system of the W c East Yorkshire hills . hen the Section rea hes the uplands Of C of the Wolds it enters the district the halk, which covers all the rest of the ground until it ends abruptly at the line of precipice that culminates at Flamborough Head . ctio n ac r o ss tlzc I sle o / M— IV . S e f W ig This Section is drawn 28 G E O L O G I C A L M A P O F E N G L AN D AND W A L E S an d in a north south direction across the Isle of Wight, on a much larger scale than the others, with the view of showing the succession of the Tertiary and Cret aceous formation s of the Of E south ngland . At the north end , the four groups of the Oligocene series are seen to occupy the low ground stretching from the Solent to the chalk downs in the middle of the island . At the top lie the Hamstead Beds, with their denuded upper surface ; underneath them comes the Bembridge group of e cl marls and lim stone, which , as the ip is gently northwards, the O are succeeded by sborne Beds, emerging towards the northern shore . It will be observed, however, that these low angles of inclination rapidly change towards th e south , until the strata become vertical , or even slightly overhang . Thus w O the, lo est ligocene group , that of the Headon Beds, is allowed to rise fro m under the sea . It is followed by the E — B rac kle sh am a ocene series Barton Clay, Beds, B gshot Sands , R — London Clay, and Woolwich and eading Beds all vertical or ff nearly so, along the coast cli s of the western and eastern m a ends of the island . Next co es the Chalk, also in vertic l ff . beds, which strike from the Needles to Culver Cli The various members of the Cretaceous system appear successively in their proper order, but as the inclination rapidly lessens, a they occupy progressively bro der tracts of the surface, until the a re Lower Cretaceous form tions cover a wide space of ground, vealing on th e western coast a part of the Wealden series . It will be seen from the dotted line that this tract lies over a a On t broad flat nticline, and that the sou h side the higher members once more appear in a d e tached outlier at St . Cathe ’ rine s Down . The blue Gault gives rise to extensive landslips a a of the Upper Greens nd and C h lk above, and thus produces ' rc li n e the picturesque scenery of the Un de fl. O of the most impressive lessons conve yed by this Section is the evidence it supplies th at extensive terrestrial disturbances have aff ected the south of England since older Tertiary time . Another lesson is the proof furn ished of the vast amount of denudation which has taken place during the same interval . G EOLOG IC AL S URV EY O F F IC E, M YN TR E ET LON D ON . 28 J ER S , , ’ I mé o r ta n t - N etv W o r k n ea r/Z R eady Tm : MET EO ROLOG Y V O LUM E will be i ssu e d in S u mm e r of 1 898 ' Bartho lo m e w s A S e rie s Of M aps Illu st ratin g th e Nat u ral Ph e n o me n a o f th e E arth . m an ne d by ! u st u s Pe r m . 4 6 5m Amy-o z Over 200 - Plates with Desc riptive Tex t P RE PA RED UNDER TH E ‘ D IREC T IO N O F ‘ G BARTH O OM E W I. . L , ! R E V IS E D A ND EDI TE D B y h — Om m Pn o r . AH RS e n s u LL D. t g p y J G , , F. R. S . . e c . Oc e a n o r a h - M U Y OH N RRA LL. D. hal g p y J , C len ge r G eo lo — n A c u l l ALD . S IR a u . L LL D. . R. t gy , D C , , F S . , e c . M e t m lb — o o ALE! ANDER BUC H AN LL D R. gy , F S . E. C o s m o g raph y — . T D . S c I M n t i Pao é e sso n . A K NOT ag e s m C , , — B o t an ROFES SOR BAYu Y BAL FO UR M . . I) . S o . y P , D , — LL D Z o o l o g y P. L — E h n o ra h ROF ESS OR . H K EAN E t g p y P A . , — De m o g raphy ELIS E: Rs c w s ' n f h e W o rk w lll be lo an e d In s u t . V o lu me s T h e vt rlo u s S e c t io . o t m , a e a c h lo c o m p let e d . J O H N B ART H O L O M EW c o . u t h e e n i u h u rg h G eo g raph ies ! i n s t it t e. T H E LIBRAR Y UN IV ERSI TY O F C ALIF ORNIA S an t a B arb ara DIS PLAY P E RI OD J AN1 9 1952 zo m ( 0208 4 8 4 4 7 6 pu rpo se 9! t h e To u r is t a n d CO M FLETE s ays . o n l o t h f o ld dd S C OTLAN D, C , , ' in 4 C ri s es ; P n lc e 62s . _ RELAND o n C l o t h f ld ed J ; , o i Pr ic is» n 1 C as e . e , ' U K K r ALu T NET- PRIC ES . S OLD AT A LL . BCO S ELLERS a e o O s s A