Kellys_Berks_Bucks&Oxon_1915_0461.jpg

BUCKINGHAM SHIRE

DI R E C T O K V . ]

examined for fossils; in this way the broad outlines we now
possess m ust be tilled up, and if only one person in each
parish could be induced to undertake such w ork, the gain
to geological inquiry would be of real and great value.
T a b l e o f t h e S t r a t a w h ic h o c c u r in
B u c k i n g h a m s h ir e .
Max. Thickness.
Formation.
Sub-division.
Feet.

f A lluvium ......................................
‘ I Valiev Gravels.
Boulder Clay ........................
Glacial G ravels and Sands
Clay with F lints ....................
| London C lay
( Reading Beds
Upper Chalk (flints)
r
Middle Chalk (few
flints)....................
Upper C retaceo u s^
Lower Chalk .......
| UpperG reensand...
( G au lt..
L o w er C retaceo us
Lower Greensand
C Purbeck Beds ....................
Up p e r O o l i t e s . . . < Portland B e d s ....................
( Kim eridge C lay ................
| Corallian B e d s ....................
M id d l e O o l i t e s .
( Oxford C la y ........................
f Cornbrash.............................
G reat Oolite C lay ............
| G reat Oolite Lim estone ...
j Upper Estuarine Series .
L o w e r O o l i t e s ..
Lower E stu­
arine Series
Inferior Oolite
Northam p ton Sand
L
L i a s ............................ Upper Lias

{

Total thickness of S trata .............................

20

30
200

17 5
150
20
250
250
25
60
100
45

400

3

120

2501 feet

T h e U p p e r L i a s . — Com mencing with the oldest rocks,

we And in the north of the county that the river Tove
has cut down into and exposed the bluish-grey Upper Lias
Clays, which ju st enter the county from between Grafton
Regis and Ashton to Castle Thorpe, tw o or three miles
north of Stony Stratford ; the Ouse has also exposed small
patches of Upper Lias near Stoke Goldington and Weston
Underwood, but there are no good sections.
T h e O o l i t e s . — (1) Inferior Oolite S eries.— Of the sandy
and slaty beds known as the Northampton Sand there are no
good sections, but they are represented by a fewr feet of
green and grey sandstone which crop out in the Ouse
valley below Biddlesden : above them lie 7 or 8 feet of
loams and white and brown sands which belong to the Lower
Estuarine Series.
(2.) The Great Oolite Series. — The G reat Oolite strata
cover much ground in North Bucks. A t their base we And
coloured sands and clays 15 to 20 feet thick, which are seen
at Stoke Goldington and Weston Underwood, and are
known as the Upper Estuarine S erie s: above them come
the Great Oolite Limestones-, and higher still we And the
Great Oolite Clap. The G reat Oolite Limestones are ex ­
posed in m any quarries; from Buckingham th ey pass
round by Stowe and Lillingston ; Stony Stratford, Newport
Pagnell and Cold Brayfield m ark the eastern lim it, but
they stretch north-eastward from these points into Bedford­
shire.
The G reat Oolite Limestones are of a compact and not
oolitic ch ara cter; they are often soft and m arly, and in
such beds fossils are most common ; frequently we And
only the m oulds or casts of shells, but they are generally
entire, arid the strata appear to have been deposited in still
water. C layey beds occur at the base, above which come
thin-bedded, cream-coloured limestones and m arls, whilst
the white, hard, Ane-grained limestones are more usually
found near the top. W est of Buckingham there are m any
quarries, as near W estbury. At. Shalstone Hill F arm there
is a bed of very hard, white limestone, composed almost
entirely of broken shells, and yielding a beautiful building
stone. In the valley of the Thornborough Brook there arc
some large quarries, exposing a section of more than 30
fe e t; a fault, with a downthrow to the east of to feet, runs
across the quarry ; very interesting exposures of “ faults,”
or dislocations of the beds, m ay also be seen in a quarrj'
P68* South End. On W hittlewood Forest (in Northants,
just beyond the county boundary) there are several quarries
IIIr- v? i
a t Oolite Lim estone ; here, on blocks of stone
wnicl» have been long exposed to the weather, one iinds
standing out in relief portions of shells, plates and spines of
sea-urchins, star-like joints of the stems of orinoids, with
worm tracks and serpulce.
F
(i? :!n ies *n the G reat Oolite Lim estone at G ayhurst,
ey, Salcey Wood an 1 Olnej- m any fossils have been

13

obtained; the brachiopod shell named 7 erebr atula max il lata
abounds here. The scenery of the tract occupied by the
G reat Oolite is undulating, hilly, and often well-wooded,
with an eastward slope to the Ouse ; the dip of the beds is
also in this direction, and their total thickness is less than
100 feet.
Great Oolite Olay or Forest Marble.— W e seem ingly have
the north-easterly end or term ination of the Forest Marble
in Buckingham shire, it is the equivalent of the “ G reat
Oolite Clay ” of other districts ; traces of it are seen in quar­
ries near the brook east of Tingew ick church, at Thornton
and Lillingston L o v e ll; the beds consist of from 3 to 12 feet
of blue or brown clay, w ith about 2 feet of hard grey slaty
limestone underneath, almost made up of oysters.
Cornbrash.— W e And the rubbly Limestones which are
known as the “ Cornbrash ” between Fringford, Tingewick
and Buckingham , north of which town they extend past
Maids Moreton and A keley ; eastwards by Thornborough
and Beachampton, the outcrop of the Cornbrash is two miles
wide ; near Stony Stratford it contracts to half a m ile, again
widening between Brad well, G reat Linford and Newport
P a g n e ll; it is then overlaid and thereby obscured b v the
Ouse gTavels, but re-appears as a narrow band, not a quarter
of a mile wide, east of Sherrington, and curves round thence
to Newton Blossomville ; the Com brash limestone is largely
quarried for road-m aking, being very hard. Near B ucking­
ham, on the Bourton road, we see hard blue limestones
associated w ith beds of black and blue clay ; close to Thorn­
borough, on the Leckham pstead road, we have in the quar­
ries good illustrations of the m anner of weathering of these
Cornbrash limestones ; the top limestone bands are yellow
and rubbly, then, under a bed of sandy clay, we have solid
limestone, yellow outside, blue within ; lastly, at the base
we find solid blue limestone only. The change in colour is
due to the iron, which exists in the lower bands of the rock
as a carbonate, whilst upwards it gradually passes into a
peroxide, under the influence of air and water percolating
dow nwards through the beds; the total thickness here is
about ten feet. Near W olverton there are several quarries ;
here the Cornbrash is of a blue-grey colour, very hard and
finely laminated ; fossils are numerous but difficult of
extraction. There are tw o curious inliers at W est Stan Hill
and Marsh G ib bon ; the first is a very low hum m ock ; a
quarry here shows loose rubbly Cornbrash, w ith a bed of
pale blue clay, full of oysters. Marsh Gibbon stands on a
little hill of Cornbrash ; there are several quarries which
show loose rubbly stone on top, then soft m arly clay, and
hard blue limestone at the bottom.
(3.) The O xford Clay, with K e ll aways Rock.— This wellknown formation is a light-blue clay, weathering yellow at the
surface, and perhaps 400 feet thick ; its western lim it is defined
by the outcrop of the beds of Cornbrash ju s t described, but
eastwards it stretches over a wide expanse to Muswall and
Brill Hills, Quainton and Fenny Stratford ; sections are not
common, but m ay sometimes be seen in brick-pits, rail wav
cuttings, or drain c u ttin g s ; towards the Ouse the Oxford
C lay occupies the top of the low escarpm ent, form ing a
heavy undulating country which rises with a short b ut steep
slope above a plateau form ed of Cornbrash
Near G oddington we have the base of the formation, here composed of
hard, cream -coloured calcareous clay, containing Ammonites
Jason, Sfc. ; sim ilar beds are exposed round Newport Pagnell,
where Ammonites calloviensis is found, w ith saurian bones,
&c. ; these basement beds probably, are near the horizon of
the KeLlaways Rock of W iltshire. The brick-pits near Padb ury show shaly dark-blue clay, w ith large nodules and
septaria of limestone. Gi-yphcea dilatata is common every­
where, with sem i-transparent glassy crystals of selenite,
called “ fossil w ater ” by the workm en, and yellowish lumps
of iron pyrites.
(4.) Tlte Coralline O olite,“ Coral Ray,” or Gorallian.— The
Corallian sands and limestone at Headington and Stanton
St. John, near Oxford, appear to pass eastwards into a clayey
band containing Ostrea sandalina, which has been traced by
Worminghall, O akley, Boarstall, round Muswell Hill, and
through Dorton to the base of Quainton Hill. A t Stud ley
there is a bed of grit, “ a sort of argillaceous chert, rich in
Pinna’-, Ammonites, and other organic remains ; ” this m ay
m ark the transition. The thickness of the Corallian Beds in
this district does not exceed 45 feet.
(5.) Kimeridge Clay.— The Coralline Oolite having become
itself a clay band, there is nothing over the greater part of
Bucks to separate the two great clay masses named after
Oxford and Kim eridge respectively, from one another ; it is,
however, considered th at the Kim eridge C lay forms the
plains and low grounds between Tham e, Brill, Waddesdon
and A ylesbury, its thickness being about 100 feet ; the lower
boundary line is drawn by the Geological S u rvey to end off
near Stew kley, but this is marked “ wholly conjectural ; ”
the Kim eridge Clay is a bluish-grey or yellow shaly clay
about 100 feet in thickness, often bituminous, sandy towards
the base and w ith irre g u la r bands of limestone nodules ; like