Kellys_Berks_Bucks&Oxon_1915_0029.jpg

d ir e c t o r y

.]

BER K SH IRE.

We shall com m ence w ith the lowest and oldest rocks
which occupy the extrem e north-west of th e county.
T h e M i d d l e O o l i t e s . — ( i) 2 he OxfordClay.
Entering
W lbte',' Eh" J ^ 'o .— Excursion to Tvvyf rd * » d t h e the cou n ty a t Coleshill and near Lechlade, and running east
1901.
W argrave Outlier. Proc. Geol. Assoc., vol. xvii., bv Thrupp Com m on and New bridge and north-east by
H inksey and W yth am towards Oxford, we have the Berk­
Monckton, H. W .— O rigin of some G ravel-Flat» of shire portion of a tract of stiff clay, which extends north­
19OX.
S u r r e y and Berkshire.
Geol. M ay., P- 5 '° \
w ards across the Tham es into Oxfordshire and G loucester­
Treacher, LI. & H. J. O. W h .te .-L x c u r8 .o n to shire
I t contains frequent bands of lim estone nodules or
19 O I.
T w yford and the W argrave Outlier. P roc. Geol. septaria, and is of a blue colour when dug at any depth,
b ut weathers yellow where exposed to the air as at or near
K m n a rd ,™ ! S. & ’ li. B. Woodward. — Post-Pliocene the surface of the g rou n d ; the O xford C lay forms a low
190 1.
and Non-m arine Mollusca of the S outh of England. tract of land bordering the Tham es for about a m ile or two
Proc. Geol. Assoc., vol. x vii., p. 213.
on its southern side, and is of little economic value. It is
Tones
T . K .— Eolithic Im plem ents at Fm cham p- m ostly in pasture and forms the cou n try round Eaton
1902.
stead Ridges. Sept. W ellington Coll. A . S. S oc., Hastings, Dencourt and B u s c o t: a boring at W ytham
passed through 596 feet of Oxford C la y. Gryphuea dilatata
W hite II. j! '1 0 .— Excursion to K in tbu ry, Inkpen is a common fossil in the O xford C la y, it has been found at
190 2.
and W oodhay.
Proc. Geol. Assoc., vol. xvn .,
Fvfield M arsh.
.
('•) The Coral Ray or “ Corallian.’ — These term s are u s e l
Shruteoie, O. A. & W . W h ita k e r.-E x c u rsio n to to designate a series of beds, cla yey and sandy at the base, of
1 9 0 2.
Reading. Proc. Geol. A ssoc., vol. x vil., p. 3 S lwhich the m iddle portion is a rubbly oolitic lim estone full
1903. L am plugh, G . W .— Belem m tes of the Fanngdon of corals, capped in a few places by irony sands. T h e
“ Sponge-G ravels.” Geol. May. p. 32.
m uddy sea in which the Oxford C lay was deposited m ust
1904. W hite H J 0 .— Excursion to Culham an a W alling­ have cleared and shallowed, and in the w arm waters corai
ford.’ Proc. Geol. Assoc., vol. x vii., p. 300.
reefs grew irregularly, resem bling those now form ing in
1905. W right, J .— Lower Greensand Foram s. from .Little tropical seas. W here present, the thickness of the Coral
Coxwell. Geol. M ay., p. 238.
Rao-varies from 10 to 30 feet, and it constitutes a ridge
overlooking the valley of the Tham es. E n terin g the county
I9° 5. Salter, A. E .— Superficial Deposits of Central, etc,
England. Proc. Geol. Assoc., vol. x ix ., p. 1.
near Shrivenham , we can trace it round Faringdon, and
Lam
plugh,
G
.
W
.N
o
t
e
on
Lower
Cretaceous
thence it occupies a tra c t three miles wide north of the
i 9° 5.
Phosphatic Beds and their Fauna. Sept. B u t . river Ock as far as Abingdon, east of Cum nor : at W ytham
Assoc, for 1904, p. 548,
,
the Corallian rises as an outlier to a height of 583 feet above
D avev, E. C .— Fossils of Greensands of W ilts and sea le v e l; it is la rg ely quarried for road m etal.
I he
I 9°SBerks.
Proc. B a th Nat. H ist. Soc., vol. x., lower portion contains ch aracteristic Ammonites, such as
A perarmatus ; corals and spines and plates of sea-urchms
Browne", A . J. J u k e s -.-T h e C lay w ith F lin ts : its occur in the m iddle portion in large num bers while
19 0 6 .
O rigin and Distribution.
Quart. J oum . Geol. A mmonites p lica tilis characterises th e upper beds. Bradle>
Soc., vol. Ixii., p. 132TT. ,
,,
. F arm , north of M archara, is a well-known locality for
W
hite,
H.
J.
O.
&
LI.
T
reach
er.—
K igher Zones of
19 0 6 .
fossils.
. nn, Koi,
Uppe’r Chalk. Proc. Geol. Assoc., vol. x ix., p. Corallian
T h e U p p e r O o l i t e s . — (1) Kim eridge Clay.
Another
378. (See also p. 349-)
. ..
e th ick mass of blue clay w ith bitum inous shales rests upon
,006. W hite, H. J. O. & LI. Treacher. Phosphatic Chalks and succeeds th e Corallian beds as we pass to the south-east.
of W interbourne and Boxford. Q. Journ. beol. This second and upper bed of clay is nam ed after the
Soc., vol. lxii., p. 499.
village of Kim eridge in D o rset; it form s flat wet land from
Shrivenham station to Longcott. Passing underneath the
T h e rocks of Berkshire have been very carefu lly studied by well-known sponge gravels of Faringdon, it re-appears
the officers of the Geological S urvey. Com plete geological south of Shellingford and Stanford, and forms the
Fields
m aps of the surface of the county w ere published in 1860-61, of E ast and W est H anney and D rayton .’
Crossing the
and in the splendid series of Survey Memoirs (see list given Ock at Abingdon, we can follow the K im eridge C iay to
above) a very fa ll account will be found of all the strata. Radley and B agley Wood. Of the K im eridge C la y fossils
The T ertia ry Eocene Beds of the south and east of Berk­ Ammonites biplex is rather com m on and b eautifu lly pre­
shire were first described by Sir J . Prestwich in a m asterly served ; Ostrea deltoidea is very abundant. T h e elay is
series of papers published between 1840 and i860 m the d u g at several places for brick m aking.
Q uarterly Journal of the Geological Society.
Professor
(2) Portland Sand.— There is a sm all outlier form ing the
Rupert-Jones and other able geologists have also w ritten on hill on which the village of Bourton is b u il t ; it is well e x ­
the same subject.
, posed in a large quarry there.
As the longest axis of Berkshire-extends nearly east and
T h e C r e t a c e o u s S y s t e m .— Th is term is derived from
west, while the different beds of rock run across it in a the Latin ‘ creta,’ chalk, the W hite Chalk being the best
slanting direction from north-east to south-west we natura ly known and most conspicuous mem ber of tbe system or
expect to m eet w ith a good v ariety of the geological form a­ group of strata of which it is the upperm ost division.
tions in the county, and this we shall find to be the case.
I . L o w e r C r e t a c e o u s F o r m a t i o n . — The Lower Green­
From the absence of disturbances, however, and from the sand .— This is a bed of loose reddish sand, often full of
dip being gentle and coinciding m ore or less with the pebbles and very variable in thickness. A t Fernham and
general easterly slope of the surface of the county, the G reat and L ittle C oxw ell it assum es considerable local im ­
variety of rocks is not so great as m igh t have been portance. constituting the “ sponge-gravels of Fan n gdon ;
expected.
it is la rg ely quarried for gravel, which from its bright
T a b l e o f t h e S t r a t a o f B e r k s h ir e .
yellow hue* is m uch sought after for walks and avenues.
M a x . T h ic k n e s s .
From B aulking eastward to the Tham es it is not seen, being
F o rm a tio n .
S u b -fo rm a tio n .
F eet.
overlapped by the G ault, b ut there is an outlier which forms
_
f A lluvium ----a hilly tra c t north of S u n n in g w ell; the Low er Greensand
R e c e n t ..................| River G ravels
m akes a lig h t dry arable soil.
( C lay with Flints
II. U p p e r C r e t a c e o u s F o r m a t i o n . — ( i ) Lhe Lrautt.—
P l e i s t o c e n e ......... { a r a Jv e i s .....................
This is a blue m icaceous clay containing occasional nodules
(U p p er Bagshot.........................
200
of limestone ; it runs as a band about one to two m iles wide
45
| Middle
,,
between A shbury and Stainsw ick north-eastw ards to
E o c e n e .....................-I Low er
,,
100
Uffino-ton, where it turns due east and reaches through
| London C la y .............................
35 °
W est Challow and Eteventon to W ittenham ; its upper
‘ Reading Beds .........................
9°
boundary is well m arked by a line of springs throw n out by
Upper C halk .............................
33 °
the im perm eable c la y ; form ing a low plain a t the foot of
*7 °
Middle ,, .............................
the chalk escarpm ent the G au lt is seldom exposed in
Upper
Lower ,,
2 I5
sections, except in an occasional b r ic k -p it; its thickness
C retaceou s
Upper G reensand.....................
9°
is about 100 feet.
. .
.
^ G a u lt..........................................
220
(2) The Upper Greensand or Chloritic Series.— From
L ow er
W ittenham Wood past W allingford to Aston T irrell the
j- Lower G reensand....................
60
C R xCTACEOUS
outcrop of this rock is not less than five miles broad.
j Portland Beds .........................
20
Follow ing it w estward through H agborne, Didcot, E ast
U p p e r O o l i t e s . . . j( Kim eridge C la y .....................
I 5°
I-Iendred and W antage the Upper Greensand rapidly
..
_
f Corallian B e d s ..........................
80
narrows, until at Childrey, S parsholt, Com pton Beaucham p
M i d d l e O o l i t e s j 0 xford C l a y .............................
450
and A shbury it only form s the slope of the escarpm ent of
chalk, which consequently becomes steeper as we follow it
Total thickness of S tra ta ................ 2,645
in this direction.
F requently the exact boundary is

1901.

Jones, Prof. T. R .— H istory of the Sarsens.

Geol.