Kellys_Berks_Bucks&Oxon_1911_0015.jpg

d ir e c t o r y .]

B E R K S H IR E .

13

We shall commence with the lowest and oldest rocks,
Jones, Prof. T. R .— History of the Sarsens. Geol. which occupy the extreme north-west of the county.
1901.
T h e M i d d l e O o l i t e s . — ( i ) The OxfordClay.— Entering
White ' ET J.4’o . — Excursion to Twyford and the the county at Coleshill and near Lechlade, and running east
I9 0 I.
W argrave Outlier. Froc. Geol. Assoc., vol. xvn., by Thrupp Common and Newbridge and north-east by
Hinksey and W ytham towards Oxford, we have the Berk­
Monckton, H. W .- O r ig in of some Gravel-Flats of shire portion o f'a tract of stiff clay, which extends north­
I90I.
Surrey and Berkshire. Geol. May., p. 5 IO-_
wards across the Thames into Oxfordshire and Gloucester­
to
I90I. Treacher, LI. & H. J. O. W h ite.-E xcu rsio nGeol. shire. It contains frequent bands of limestone nodules or
Twyford and the Wargrave Outlier.
septaria, and is of a blue colour when dug at any depth,
Assoc., vol. x vii. , p. 176.
r>T
but weathers yellow where exposed to the air as at or near
I90I. Kennard, A. S. & B. B. Woodward.— Post-Pliocene the surface o f‘ the ground; the Oxford Clay forms a low
and Non-marine Mollusca of the South of England.
tract of land bordering the Thames for about a mile or two
Proc. Geol. Assoc., vol. xvii., p. 213.
on its southern side, and is of little economic value. It is
Ï902. Jones, T. R .— Eolithic Implements at Finchamp- mostly in pasture and forms the country round Eaton
stead Ridges. Rept. Wellington Coll. A . A. Soc.,
Hastings, Dencourt and B u sco t: a boring at M vtham
passed through 595 feet of Oxford Clay. Grypluea dilatatn
1902. W hite H. j f 0 .— Excursion to Kintbury, Inkpen is a common fossil in the Oxford Clay, it has been found at
and Woodhay.
Proc. Geol. Assoc., vol. xvii.,
Fyfield Marsh.
‘ (2) The Coral Ray or “ Corallian.” — These terms are use 1
1902. Shrubsoie, O. A. & W. W h itaker.-E xcu rsio n to to designate a series of beds, clayey and sandy at the base, of
Reading. Proc. Geol. Assoc., vol. xvii., p. 381.
which the middle portion is a rubbly oolitic limestone fuU
Lamplugh, G. W. — Belemnites of the Fanngdon
1903 .
of corals, capped in a few places by irony sands. The
“ Sponge-Gravels.” Geol. May. p. 3 2muddy sea in which the Oxford Clay was deposited must
White
H. J. 0 .— Excursion to Culham and W alling­
1904 .
have cleared and shallowed, and in the warm waters corai
ford.’ Proc. Geol. Assoc., vol. xvii., p. 3°°reefs grew irregularly, resembling those now forming in
1905 . W right, J .— Lower Greensand Forams. from Little tropical seas. Where present, the thickness of the Coral
Coxwell. Geol. May., p. 238.
Rag varies from 10 to 30 feet, and it constitutes a ridge
Salter,
A.
E
.—
Superficial
Deposits
of
Central,
etc.,
I 9°S.
overlooking the valley of the Thames. Entering the county
Eno-land. Proc. Geol. Assoc., vol. xix., p. 1.
Lamplugh, G. W .— Note on Lower Cretaceous near Shrivenham, we can trace it round Faringdon, and
I 9 °5 .
Phosphatic Beds and their Fauna. Rept. B rit. thence it occupies a tract three miles wide north of the
river Ock as far as Abingdon, east of Cumnor : at Y\ ytham
Assoc, for 1904, p. 548.
1 the Coraliian rises as an outlier to a height of 583 feet above
1905. Davey, E. C .— Fossils of Greensands of Wilts and sea le v e l; it is largely quarried for road metal.
The
Berks. Proc. Bath Nat. Iiist. Soc., vol. x.,
lower portion contains characteristic Ammonites, such as
p, 412.
A . perannatus ; corals and spines and plates of sea-urchins
Browne,
A.
J.
Jukes-.—
The
Clay
with
F
lin
ts:
its
1906.
Origin and Distribution.
Quart. Joum . Geol. occur in the middle portion in large numbers, while
Ammonites plicatilis characterises the upper beds. Bradley
Soc., vol. lx ii.,p . 132.
Farm , north of Marcham, is a well-known locality for
I9O6. White, H. J. O. k LI. Treacher.— Higher Zones of Corallian fossils.
Upper Chalk. Proc. Geol. Assoc., vol. xix., p.
T h e U p p e r O o l i t e s . — (1) Kimeridge Clay.— Another
378. (See also p. 349-)
,,
White,
H. J. 0 . & LI. Treacher.— Phosphatic Chalks thick mass of blue clay with bituminous shales rests upon
Ï9O6.
and
succeeds the Coraliian beds as we pass to the south-east.
of Winterbourne and Boxford. Q. Journ. Geol.
This second and upper bed of clay is named after the
Soc., vol. lxii., p. 499.
village of Kimeridge in Dorset : it forms flat -wet land from
Shrivenham station to Longcott. Passing underneath the
T h e rocks of Berkshire have been very carefully studied by
the officers of the Geological Survey. Complete ^geological well-known sponge gravels of Faringdon, it re-appears
maps of the surface of the county were published in 1860-61, south of Shellingford and Stanford, and forms the “ Fields
and in the splendid series of Survey Memoirs (see list given of East and West Hanney and Drayton.” Crossing the
above) a very full account will be found of all the strata. Ock at Abingdon, we can follow the Kimeridge Clay to
The Tertiary Eocene Beds of the south and east of Berk­ Radley and Bagley Wood. Of the Kimeridge C lay fossils
shire were first described by Sir J. Prestwich in a masterly Ammonites biplex is rather common and beautifully pre­
series of papers published between 1840 and i860 in the served ; Ostrea deltoidea, is very abundant. The clay is
■Quarterly Journal of the Geological Society.
Professor dug at several places for brick making.
(2) Portland Sand.— There is a small outlier forming the
Rupert-Jones and other able geologists have also written on
hill on which the village of Bourton is built ; 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 . — This term is derived from
•west, while the different beds of rock run across it in a
the
Latin
‘ creta,’ chalk, the White Chalk being the best
.slanting direction from north-east to south-west we naturally
expect to meet with a good variety of the geological forma­ known and most conspicuous member of the system or
tions in the county, and this we shall find to be the case. group of strata of which it is the uppermost division.
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
dip being gentle and coinciding more or less with the sand.— This is a bed of loose reddish sand, often full of
pebbles
and very variable in thickness. A t Fernham and
general easterly slope of the surface of the county, the
variety of rocks is not so great as m ight have been Great and Little Coxwell it assumes considerable local im­
portance, constituting the “ sponge-gravels of Faringdon ; ”
•expected.
it is largely 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 Be r k s h ir e .
yellow hue* is m uch sought after for walks and avenues.
M ax. T hickness.
From Baulking eastward to the Thames it is not seen, being
Sub-form ation.
Feet.
Form ation.
overlapped by the Gault, but there is an outiier which forms
I Alluvium ................................
20
R e c e n t ..............
a hilly tract north of Sunningw ell; the Lower Greensand
* ( River Gravels ........................
20
makes a light dry arable soil.
( Clay with Flints ...................
20
P l e i s t o c e n e ...
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 ) The Gault.—
* j G ra v e ls....................................
15
This is a blue micaceous clay containing occasional nodules
f Upper Bagshot........................
200
of
limestone ; it runs as a band about one to two miles wide
| Middle
„
45
between Ashbury and Stainswick north-eastwards to
E o c e n e ...................^ Lower
,,
100
Uffington,
where it turns due east and reaches through
] London C lay......................
35°
West Challow and Steventon to Wittenham ; its upper
(^Reading Beds ........................
9°
boundary is well marked by a line of springs thrown out by
33°
f Upper Chalk...........................
the impermeable c la y ; forming a low plain at the foot ot
I Middle ,,
17°
Upper
the chalk escarpment the Gault is seldom exposed in
■
I Lower ,,
215
C retaceous
sections, except in an occasional brick-p it; its thickness
Upper Greensand....................
90
is about 100 feet.
^ G a u lt........................................
220
(2) The Upper Greensand or Chloritic Series.— From
L ow er
| Lower Greensand...................
60
Wittenham Wood past Wallingford to Aston Tirrell the
C retaceous
outcrop of this rock is not less than five miles broad.
U p p e r O o l i t e s . . . » B o r tla n d B e d s .............................
"
Following it westward through Hagborne, Didcot, East
( Kimeridge Clay ...................
15°
Hendred and Wantage the Upper Greensand rapidly
f Corallian B ed s.......................
80
M id d l e O o l it e s
narrows, until at Childrey, Sparsholt, Compton Beauchamp
( Oxford C la y ............................
45 °
and Ashbury it only forms the slope of the escarpment of
chalk, which consequently becomes steeper as we follow it
.. 2,645
Total thickness of Strata.,
in this direction
Frequently the exact boundary is