Kellys_Berks_Bucks&Oxon_1915_0462.jpg

BUCKINGHAMSHIRE.
the Oxford C la y, it is best fitted for pasture land ; oaks grow
well upon it : from the im pervious nature of this wide clay
tract there are no springs. Near H artwell and Aylesbury
the Kim eridge clay is largely worked for brick-m aking ;
here it is of a dull leaden colour, lignite (fossil wood)
is common and fossils abound ; Ammonites biplex occurs,

Diagram Section of small faults in the Portland Stone, Brill.

[ k e l l y ’s

(2.) The Upper Greensand.— This form ation overlies the
G ault and extends from between Henton and Princes Risborough to about a mile north-east of Buckland, from which
point it is hardly traceable, although it is once m ore seen in
the brick-yard at Eaton Bray ; here we have six feet of palegrey m arl, underlaid by the same depth of greenish sandy

This dislocation of the beds was seen in a small pit about two-thirds

of a mite south-west of the church. The dark bands are two shaly layers ; the greatest displacement, or “ throw ,” only amounts to two
feet. (A fter A . H. Green, Geol. Survey.)
w ith the original beautiful shelly lustre still preserved, and clay. A t Buckland the Upper Greensand is seen in the
m any of the other fossils sparkle w ith iron pyrites and are sides of a pond, and a stream cuts through it about half a
mile south-east of Aston-Clinton church ; at Risborough the
found entire and in great perfection.
(6.) Portland B ed s.— The lower part is sandy, above Upper Greensand is, perhaps, 20 feet t h ic k ; in the road
which come beds of limestone, the whole being about 60 feet
in thickness, the main outcrop passes north-east from Tham e
by Cuddington and Dinton to A ylesbury and B ierto n ; out­
lyin g masses occur at M uswell Hill, Brill, Ashendon, W hit­
church &c. There are several sections at Brill, where the
Portland Stone is quarried for b u ild in g ; here, at the base,
we see the Portland Sands with green grains, and then lim e­
stones with bands of clay and g rit, altogether about 25 feet
thick ; in one pit, south-w est of the church, a num ber of
CTJ S> 3 - c t D ‘ B ‘ Î P ' p O '
sm all faults were seen, dislocating the beds about two feet
-1 iWffgsrwsr
a t each step. [See Diagram Section above]. Near Ayles­
IS-g-g-g-li-i Sb u ry the Portland limestone is called “ pen dle” ; it is soft
a a 5 oo ** * * ' **
and sandy.
The shells, Triyonia gihbosa with Cardium
Ê S - r S l l 3 . si
dissim ile are the m ost com m on fossils.
(7.) Purbeck B ed s.— These are thin-bedded limestones
and clays of freshwater origin ; they com e above the Port­
land beds at Brill, also capping the ridge between W hit­
church and O ving, and they crop ou t east of Cuddington and
south-east of Stone ; the limestones are drab-coloured, closegrained, and in beds six or eight inches t h ic k ; the total
thickness is about ten f e e t ; fish teeth and scales occur, with
the little crustacean known as Cypris.
T h e C r e t a c e o u s F o r m a t i o n .— A great break, or interval
of tim e, of which no strata are found to bear record in
Britain, occurs a t the top of the Oolites. The succeeding or
cretaceous beds are so named after their m ost conspicuous
m em ber— the W hite Chalk [L atin , creta, chalk.]
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 sandy beds at
the base of the Cretaceous strata, known as the Lower Green­
sand, are very irregular in occurrence ; in the north-east of
the county th ey are called the Woburn sands, which extend
southwards from G reat and L ittle Brick hill to Fenny S trat­
ford, where they are overlapped by the G ault C la y ; here
they form dry, hilly ground ; on a hill near G reat Brickhill
there is a section 30 feet deep, showing coarse reddish sands
resting on Oxford C la y ; scattered through the sands are
“ red coprolites,” or phosphatic nodules, for which the
sands used to be sifted, the coprolites being then ground u]
for m anure ; the same bed occurs at Rushm oor brick-yan
an d at Potton, in Bedfordshire, and at Up ware, near
Cam bridge. More than tw en ty species of fossils native to
the bed have been found at Brickhill by Mr. W. Keeping,
besides num bers washed out of lower formations, especially
the Kim eridge Clay.
At Wavendon there is an outlier
containing seams of fullers’ earth ; passing southwards the
Lower Greensand crops ou t again to the south of Stone ;
here it rests partly on Purbeck, p artly on Portland beds, and
presents indications of Wealden beds a t its base. A t H art­
well a bed of brown and white sand, about eigh t feet thick,
has been used for glass-m aking; there is a sm all outlying
patch south of Oving, and others on Muswell Hill, Brill,
north of Chearsley, &c. ; the main mass crops out again
north of Haddenham.
Quainton Hill is also capped by
Lower Greensand.
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 . ) G ault.— This
is a thick mass of pale-blue clay, sometimes shaly, often
w ith layers of whitejr-brown phosphatic nodules. Entering
the cou nty in a broad band three miles wide, extending from
Tow ersey to H enton, we can trace it by Weston T urville to
H u lco tt; here the outcrop broadens to seven miles between
Cubbington and W ing on the west and Buckland and Eaton
B ray on the east. Th e manner in which the G au lt overlaps
the Lower Greensand we have already seen ; its thickness is
x Çy y 3 / 9 p
about 130 feet in the south and 250 feet in the noith-east of
Buckingham shire, and it is d u g for brick and tile m aking. cu ttings about Bledlow and Henton we see beds of crum bling
A rich seam of “ black coprolites” is found about 40 or 50 whitish sandstone, sometimes hard, and these are covered
Numerous
feet below the top of the G a u lt ; it has been worked at by clayey dark-green sand seldom exposed.
springs burst out at the junction of the Upper Greensand
Edlesborough, Puttenham , Cheddington, Xorthall, &c.