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14

Upper Lias Clays.— These

OXFORDSHIRE.

[ k k l l V s

are bluish clays which once The following classification of the strata of the Lower
everywhere rested upon and covered up theMarlstone ;they Oolites isby Mr. E. A. Walford :—
have been so denuded, however, asnow only to existatthe
T a b l e o f t h e L o w e r O o l it e s o f No r th
surface in narrow strips, and in detached patches called ;
O x f o r d s h ir e .
outliers. As we followthem alonga narrow strip on each 1
side ofthe valley oftheEvenlode theseUpper Lias Clays be- !1 5 . Thick-bedded Limestones [UpperZone]A G r e a t
come thinner and thinner, until between Charlbury and 14. Marls and Limestones [Lower Zone] ( O o l i t e ob
Stonesfield they entirely disappear. It results from this 13 Stonesfield Slate Series („ owerZone] f B a t h o n u n
that a boring, say near Oxford, might possibly reach coalat
and Lower Limestone )L
(130 ft.).
a depth oflessthan 2,000 feet. In sections near Banbury 12. Black, Brown and Green Clays, withA
the Upper Lias beds are very fossiliferous, containing
Neara................
S ubnumerous Ammonites, &c This district has been well 11. Limestone with Coral.......
i
a
worked foritsfossilsby Messrs. T. Beeslev and E. A. Wal- 10.
Do. with Astarte, &c....
B
athford, of Banbury.
9. Marly do., with Perna and j to
Near a .................
gi
1
OMAN,
T e l e O o l i t e s . — The Oolites of Oxfordshire can be
8. Black Clay ............. , "
separated into seven principal divisions, some of which can 7. Plant-bed Limestones, with vertical-)
be again sub-divided (1.) Inferior Oolite. In North Oxford­
( S ° ft.)
markings................ >shire we find, resting upon the Upper Lias Clays, some 6. Chipping Norton Limestone:30 ft... J J
sandy beds, here changing into a white oolitic freestone, as 5. Sand and LimestoneswithTrigonia']
at Brailes Hill, or intoironstone, as at Mine Hill Shenlow
signata ................. I I n f e r io r
Hill, which risestoa height of 830 feet,iscapped withthese 4. Clypeus
Grit [with A. Parkinsonij :|
sands, as isalso Epwell Hill, a little south of it. South of
ft................... }
■ O o lite .
these points,the sands spread out considerably, covering the 3. Sh20
elly Limestone............ I
Rollright Ridge, and extending southwards to Chipping 2. Upper Trigonia-Grit.......... | (35 ft.)
Norton, and eastwards to Duns Tew and Steeple Aston. 1. Fawn-coloured Limestones ...... J
The term Northampton Sand has been applied to these
sandy beds,,butitisveryimportant to undei’stand thathere The Neseran Beds are so named from the presence in
they reallyinclude two formations : (a) the lower part con­ them ofthe bivalve shell Necera ibbetsoni: they appear to
tainingmarine shellsand belonging to the Inferior Oolite, be the local equivalent of the Upper Esluarine Series of
and (6)the upper portion, almostdestitute of fossils,except Lincolnshire; while the Chipping Norton Limestone
wood and plant markings, and belonging tothe Great Oolite (whose maximum thickness is30 feet) may representsome
age In fact in North Northamptonshire and Lincolnshire p
art of the Lincolnshire Oolite Limestone. In the above
we have a thick bed of limestone lying between these two ta
le Mr. Walford calls the strata Nos. 6 to 12 “Subsandy beds ; but in Oxfordshire this limestone iswanting, Babthonian
thus allying them with the Great Oolite
oratallevents difficultofidentification, and (except for the Series,but”—
geologists would prefer rather to group
different fossilswhich they contain) the Great Oolite Sands them with tmany
e Inferior Oolite below ;perhaps they may be
above are hard to separate from the Inferior Oolite sandy considered h
a
s
“
p
a
ssage-beds,” linking the two formations
beds below. Ammonites Murchison« isa very characteristic together.
1
fossilofthe lower divisionorNorthampton Sand.
(2.) Great or Bath Oolite. At the base of this well- Forest Marble.— This term is applied to the hard f
known seriesoccursthe “Stonesfield Slate,” which isreally a limestones, much ripple-marked and false-bedded, which
laminated sandstone, splitting readily along the bedding compose the larger portion of Wychwood Forest. They
planes into slabs thin enough to be used for roofing. The are quarried forwall-building and forpaving-flags, and are
working ofthe “ slates” isveryexpensive,and theyare now often composed of broken fossil oyster shells cemented
only used for any special architectural effect. They have together by carbonate of lime. This formation is very
producedalargenumber offossils,indicatingtheirformation fragmentary and occupies more ground as outliers than
in shallow water. Trigonia impressa is the commonest along the outcrop ; in the Forest area it is 25 feet thick.
shell; but the most remarkable fossils are the lower jaws In the largeoutlierat Blenheim Park the Forest Marblehas
of four small species of mammals, which are the oldest become reduced to 1 5 feet, and then south of Tackleythe
mammals known exceptthose found inthe UpperTrias. In bed seems to die out altogether. The formation again
similar beds at Sarsden, the Earl of Ducie obtained the appears, however, on the leftbank ofthe Cherwell,opposite
lower jaw of a pterodactyle— an extinct species of flying Enslow Bridge; here it has become clayey and isworked
reptile. Many sections of beds belonging to the lower part for brick-making. At Middleton Stoney and Bucknell the
ofthe Great Ooliteare exposed on both sides of the valleys ForestMarble can also be recognized, but then thinsaway
of the Evenlode and the Dome. At Taynton, near Burford, rapidly ;itforms a poor soil. It is the equivalent of the
these beds have been extensively quarried, and the oldest Great Oolite Clays.
buildings in Oxford are of stone obtained from this spot,
which also furnished the material for Blenheim Palace, and Cornbrash.— This is a rubbly cream-coloured or brown
band oflimestone about 10 or 15 feetthick, which isascon­
forthe inside stone-work ofSt. Paul’sCathedral.
stant in itsoccurrence as the Forest Marble is inconstant.
The upper part of the Great Oolite is in Oxfordshire a From the village of Broughton Poggs in thesouth-westof
thick-beaded white limestone, compact or marly, and about Oxfordshire we can trace the Cornbrash by Broadwell and
20 or 30 feetinthickness. Entering thecounty near West- Kencott to Norton Bridge, where there aregood sections.
well itpasses by Burford and Wychwood Forestand spreads Passing round Witney the outcrop narrows from above a
out into a flat plateau on which stand Ditchley Park, Kid- mile to about 2 0 0 yards orso. At Bladon it broadensout
dington, Wootton, &c. Crossing the Cherwell theoutcrop again to Woodstock and Shipton;hereaboutsthe Cornbrash
isnarrowed by that stream ;good sections are exposed in is very fossiliferous. From Middleton Stoney to Bicester
the quarries at Enslow Bridge, where bones of saurians, thislimestone forms a broad plateau more than two miles
especially Teleosaurus, are not uncommon ; thence this wide, and then from F'ringford and Coddington itcircles
Great Oolite Limestone passes northwards by Stoke Lyne, round to Stratton Audley, and thence north-eastwards out
Cottisford and Mixbury. The total thickness of the Great ofthe county ; itforms a “ brasby ” loosesoilof a reddishOolitebeds in this district is about 150 feet. Fossils are brown hue, Avell adapted for the growth of wheat. A
numerous, about 150 species being recorded, thick stone- curious row' of Cornbrash inliers occurs at Islip, Charlton,
bedsalmost entirely composed of thebrachiopodshellknown and Blackthorn Hill ;these are dome-shaped masses, rising
as Terebratula maxillata are frequentlyexposed in quarries, out ofthe dullplainofOxford Clay, and itisworth noticing
how they have allbeen seized upon in past ages assitesfor
as atEnslow Bridge.
villages. Avicula echinata isa common Cornbrash fossil.
R e s e a r c h e s in t h e L o w e r O o l i t e s o f N o r t h O x f o r d ­
s h i r e . — The O
olites are grandly developed in the Cottes- (3) The Oxford Clay.— The Oxford Clay or “clunch,’as
wold Hills on the west, and also in Lincolnshire to the William Smith called it, is a very thick blue clay which
north-east of Oxfordshire. But in the Midland area the weathers yellow at the surface, and covers a broad tractof
same strata are much thinner, and the beds are often dis­ country, the scenery of which is remarkably dulland un­
continuous, changing in character from point to point interesting. Entering the county west of Kelmscott, it
as they are foJlow'ed along the strike. But in recent forms all the district between Bampton, Ducklington,
years the researches of Mr. H. B. Woodward, and of Mr. Church Handborough and Bletchington on the north,and
E. A. Walford (whose position as a resident at Banbury the Thames on the south. Then extending from Kidlington
has given him special facilities for the work) have done to Oxford we can follow it due north-east over thedrear)
much to clear up matters, although the entire district ground ofOt Moor, andpastLaunton and Piddington. There
sadly needs re-mapping by the Geological Survey with the are some outliersof the Oxford Clay on Wychwood Forest
aid of the large-scale 'six inches to the mile) maps which and one atCombe :at Oxford it is about 450 feet thick.
Sectionsare rare and fossilsscarce. Near Bicester itisdug
are now available.