45°

CHAPTER XX.

NORTHAMPTONSHIRE.

pNCLUDING CONTIGUOUS PARTS OF RUTLAND AND WARWICKSHIRE.)

By BEEBY THOMPSON, F.G.S., F.e.S.

HE district has been visited by the Geologists' Association T on ten occasions, as detailed below: LONG EXCURSIONS.-May, 1874 (Northampton, Stamford, etc.}, Proc, Geo], Assoc.. vol. iv, p. 123.; May, 1891 (Northampton and neighbourhood), Proc. CIa!. Assoc., vol. xii, pp. 172-190. DAY EXCURSIONS.-1894 (Wellingborough), Proc, Geoi. Assoc., vol. xiii, pp. 283-291 ; 1895 (Brigstock and Geddington), Proc, Ceo!. Assoc., vol. xiv, pp. II4-118; 1896 (Catesby Tunnel), Proc. Geoi. Assoc., vel, xiv, pp. 421­ 430; 1897 (Peterborough), Proc, Geol, Assoc., vol, xv, pp. 188-193; 1898 (Hillmorton and Rugby), Proc. Geoi. Assoc., vol. xv, pp. 428-433; 1899 (Weldon, Dene, and Gretton), Proc, Geoi. Assoc., vol, xvi, pp. 226-231 ; 1900 (Kettering and Thrapston), Proc, Geol. Assoc., vol. xvi, pp. 516-517; 1906 (Stamford, Collyweston, and Ketton), Proc, Geo], Assoc., vol. xix, pp. 367-370,

PHYSICAL FEATURES.

Northamptonshire is an oval county lying athwart central England, its greatest length being from north-east to south­ west, and its tapering ends pointing approximately to the Wash and Bristol Channel respectively. The greatest length of the county being very nearly that of the strike of the various geological formations, it follows naturally that certain rocks, the Great Oolite Limestone, for instance, may be at the surface from one extreme to the other. Northamptonshire may certainly be described as a hilly county, although its attenuated north-easterly end merges into the Fens. The hills are of no great height relatively or actu­ ally, but in many parts hills and valleys alternate rapidly. North-eastward from Northampton, the county gives the im­ pression of a fiat area intersected by numerous stream­ valleys-that is to say, the valleys are the conspicuous features; but to the westward and north-westward the impression is rather that of hills rising out of a plain, very decided isolated hills or ridges of land being common. The high ground which borders the western part of the NORTHAMPTONSHIRE. 451 county from near Banbury to Husbands Bosworth is a part of the main watershed of Central England, being essentially a continuation of the Cotteswold escarpment. This range of hills, which may be described as the Northampton Heights or North­ ampton Uplands, is the source of origin of several rivers. On its northern side (north-westerly part of the county), near to where the high land crosses into Leicestershire, between Rugby and Market Harborough, rise the river WeIland, which flows into the Wash, and the Warwickshire Avon, which flows into the Severn. On the inner or southern side of the same hills, near the same place, rise the Ise, a tributary of the Nene, joining the main river at Wellingborough, and the northerly branch of the Nene, which meets the westerly' branch at Northampton. On the southern side of the same range in the south­ westerly part of the county rise the river Cherwell, which flows into the Thames, and the Tove, an important tributary of the Great Ouse. The river Nene drains by far the larger part of Northarnp­ tonshire, its two main feeders being the northerly branch already mentioned, and the westerly branch rising from the inner side of the same range farther south near Staverton. The Nene beyond Northampton is a "strike" stream; it runs near the eastern border of the county, and all the main feeders flow into it from one side only, the northern. No river flows into Northamptonshire from another county.

GEOLOGY.

Northamptonshire is essentially constructed of Jurassie Rocks, though older rocks have been encountered in deep bor­ ings, and various Post-Tertiary deposits cover quite a consider­ able part of the county. Below are given in a tabulated form the various formations encountered in descending order, with their approximate maxi­ mum thicknesses: Approximate maximum thickness. ft. RECENT . River Alluvium IS RECENT AND r Fen-land • ? PLEISTOCENE i Valley gravels ..... ? Post-glacial gravels .... 30 Upper, Chalky, Boulder Clay. .. 100 PLEISTOCENE JMid-glacial gravels and sands •• 35 Lower Boulder Clay and sands .. lPre-glacial (or Preliminary glacial) sand :} 170 MIDDLE f Oxford clay . 70 OOLITES / Kellaways beds 10 452 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. Approximate­ maximum thickness. ft. Cornbrash .• IS GREAT Forest Marble series 8 OOLITE Great Oolite clay . 12 SERIES. { Great Oolite limestone 25 Upper Estuarine beds. ...• 4(} Lincolnshire Oolite .••.. 85 INFERIOR Lower Estuarine beds (part of Northampton OOLITE. { Sand)...... 15 SERIES. Ironstone series of the Northampton Sand . 60 U pper Lias . 200 LIAS. { Middle Lias • 100 Lower Lias. ...• 520 Rheetic •.•... 6 NOT 3 Trias •....• 10 EXPOSED 7 Carboniferous limestone and shales to 19° AT THE Old Red Sandstone (?). .. to SURFACE. 105 1Archeean ....• to 74

DESCRIPTION OF THE VARIOUS ROCK MASSES.

ARCHEAN. The oldest rock encountered in Northamptonshire was a quartz-porphyry, identical in appearance with one to be found at High Sharpley, in Charnwood Forest, Leicestershire. It was encountered in a trial boring for coal, at Orton, in 1883-4, 341 ft. below a.D., and was penetrated to a thickness of 74 ft. The total depth from the surface was 789 ft. There is little doubt that the Charnian axis is continued to and beyond Orton.*-

OLD RED SANDSTONE. The oldest stratified formation so far encountered in North­ amptonshire consists of coarse red sandstones, grits, and marls, believed to represent the Old Red Sandstone, as it is overlain by Lower Carboniferous Shales. This was discovered in a deep boring for water, at Gayton, some five miles south-west of Northampton. It was encountered at 417 ft. below a.D., and was penetrated to a thickness of 105 ft., the total depth from the surface being 994 ft.

LOWER CARBONIFEROUS ROCKS.

Rocks of Lower Carboniferous age were proved to be 190 ft. thick at Gayton, and at Northampton (Spinny Boring, Kettering Road) boring was stopped after passing through 4st ft. of them. * "Final Report of Royal Commission on Coal Supplies. ,,. (I905), part ix. Sub­ by Percy F. Kendall, F.G.S. NORTHAMPTONSHIRE. 453 In all the deep borings an old land surface has been encoun­ tered, on which rest littoral deposits of Triassic age. At Orton this land surface consists of quartz-porphyrite at 341 ft. below O.D. ; at Gayton of Lower Carboniferous Rocks at 417 ft. below O.D. j and at Kettering Road, Northampton, of higher beds of the Lower Carboniferous Series at 527i ft. below O.D. All rocks between the Carboniferous Limestone and the Trias are absent so far as present evidence goes. *

TRIAS. The Trias has been found more or less in all the deep borings, and since it is followed in some cases by well-developed Rhretic beds, it can fairly confidently be classed as Keuper. In all the sections, excepting Orton, it yields salt water. At Rugby the Trias was 667 ft. thick under 458 ft. of Lias and 10 ft. of Rheetics.

RHlETIc. The Rhretics were found well developed at Gayton and were recognisable at Orton although largely conglomeratic, and so it is assumed that the Upper Conglomerate of other sections is mostly of Rhretic age, though portions may be of Lower Liassic age.

LOWER LIAS. The lowest beds exposed in Northamptonshire and the immediate neighbourhood are the clays and limestones of the Lower Lias, and every well-recognised zone of the Lower Lias is or has been exposed in or near the district embraced by the title of this paper. t The Planorbis-zone has been exposed at Church Lawford and King's Newnham to the west of Rugby, and Ammonites planorbis has been recorded from both localities (Report of Rugby School Nat. His. Soc., 1877, p. 48). 1fr. H. B, Woodward (Jurassic Rocks of Britain, Vol. III, p. 162) gives a section at the former locality showing Paper Shales about 20 ft. thick overlying Rhretic Beds and Keuper. A slab of lI1odiola minima (?) from Kingsthorpe shaft possibly indicates this zone near North­ ampton, The Angulatus and Bucklandi-zones are to be seen in the fine

• For further particulars respeiting Palseozoic Rocks and Old Land Surface, etc., see H.]. Eunson, Quart. [ourn, Geol, Soc., vol. xl, p. 482, and f ourn, Nortbamotonshire Nat. Hist, Soc., vol. iv. p. 57. + Only those fossils win be recorded which are of use in identifying the zone or set of beds in which they occur, or which for some other reason are interestinz to record. 454 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. sections near Rugby. No separation of the zones can be made out in these quarries. The Rugby Portland Cement Co.'s Works at New Bilton, and the Rugby and Newbold Cement Works were visit ed by the Association in 1898. These are perhaps the finest Inland sections of th e Lower Lias Limestones to be seen in the country, and the characteristic banded structure due to frequent alternations of clay and limestone is well seen in a quarry at Newbold-upon-Avon near Rugby, a view of which is given in the " Memoir on the Jurassic Rocks of Britain," Vol. III, p. 164, and reproduced in our PROCEEDINGS, Vol. XV, p. 432. The anticline shown in the illustration is not well seen now. The limestones here yield a good deal of water, some 12,000 gallons per hour . The chief fossils found in these pits near Rugby are: Ammonites angulatus, A. bucklandi, A. conybeari, A. rotiformis, Gryphaa arcuata, G. cymbium (?) , large Lima gigantea, and Rllynchonella calcicosta. The Semicostatus or Turneri-zone.-A brickyard at New Bilton, near the Rugby Portland Cement CO.'s Works, but at a somewhat higher level, is peculiarly unfossiliferous, but it has yielded at least one specimen of Ammonites semicostatus, and so perhaps should be considered as belonging to the lower part of the Semicostatus-zone. This would make the zone of consider­ abl e thi ckness. The upper part of the zone was well exposed for a short time in the cuttings for th e Great Central Railway, a little south of Rugby (seen by the Associat ion in 1898) . H ere good typical examples of Ammonites semicostatus and A. turneri, and of the allied species, such as A . bounardi and .4. brookei, were abun­ dant, as also in some Drift Beds immediately above in one pla ce. Ammonites sauzcanus was also fairl y common. Numerous gas­ teropods are found in the zone, but the more interesting (rare) forms which the writer has in his collection came from a single block of stone found in the drift on the railway near Crick. About 25 species of fossils altogether were obtained from this one ston e, including numerous young specimens of A . semi­ costatus, T he Obtusus-zone was clearl v identified above the Semicos­ tatus-zone in the cuttings of the "Great Central Railway south of Rugby. This is interesting, becau se the writer is unaware of any other record of the zone from the Midland Counties. The thi ck­ ness of the zone is small, probably not more than 20 ft. j but this is not certain, because the upper limit consisted of a line of limestone blocks which were striated and somewhat disturbed by glacial action, and all above was boulder clay. These blocks were the chief repository of large specimens of Ammonites obtusus, The fossils found in this line of limestone nodules and the clay below included: Ammonites obtusus, ./1. stellaris, A. birchii; H ip-po-podium ponderosum, Leda renevierei, and L. galathea. NORTHAMPTONSHIRE. 455 The Oxynotus-eone was fully exposed for a considerable distance on each side of the Great Central Railway north of the Hillmorton and Dunchurch Road Bridge in 1896-7, and was seen in part by members of the Association in 1898. It was about 25 ft. thick, including the next sub-zone, and very full of fossils; its limits are fairly well defined by three abundant ammonites-A. oxynotus, A. folymorphus, and A. biter. Some of the ammonites are pyritized, but apparently none of the other fossils, and the clay is ordinary clay. Over 100 species of fossils have been obtained from the zone at this one place, hence the list below is necessarily much abbreviated: Ammonites oxynotus (hundreds), A. biter (hundreds), A. polymorphus (hundreds), A. trivialis, A. planicosta, A. raricostatus , A. tardecrescens, Belemnites acutus, Pleurotomaria anglica, Dentalium etalense (great numbers), Cardinia listeri, Hippopodium ponderosum (great numbers), Protocardium oxynoti, IValdlJrimia numismalis, Rhynchonella variabilis, SpirijeTina walcotti, etc., etc. The Raricostatus-zone.-The writer tried to ascertain the limits of this zone, and for the small ammonites which he con­ siders to be A. raricostatus, the limit appeared to be 7 ft. or 8 ft. on the slope-say 3 ft. or 4 ft. vertical only. A. oxynotus itself does not pass into this zone, but some ammonites of the beds below do; and A. tardecrescens possibly, and some others cer­ tainly, pass into the zone above. The following fossils occur: Ammonites raricostatus, A. tardecrescens, A. subplanicosta, A. densinodus, and A. trivialis. The Armatus-zone.-This zone was also fairly well exposed in the cuttings for the Great Central Railway, immediately above the last, and also on the south side of the Dunchurch Road Bridge. It was also to be seen in two brickyards at Hillrnorton (one now being filled in). Satchell's brickyard on the Rugby Road went to the base of the ATmatus-zone, and in a deeper part dug as a sump for water into the Oxynotus-zone. There is a decided difference between this zone and the zones below: the clay is less homogeneous, and weathers to a lighter colour, nodules are smaller and more numerous, and almost always ruddy when they contain a fossil; in other cases they may be of the normal colour of the unweathered clay. Small, moss-like masses of iron pyrites are common. Ammonites are abundant, but the majority are small and partially enclosed in nodules, only the outer ring or a part of it showing. Some of the larger free ammonites are a brilliant yellow from a thin coating of iron pyrites, but are difficult to preserve in this condition. The number of species of fossils to be found in the zone probably exceeds 40. In the following selection of fossils only those are recorded which fairly certainly belong to the zone: Ammonites guibalianus, A. ziphus, A. subplanicosta (great numbers), A. armatus, A. densinodus, Wright, and varieties (great numbers), 456 GEOLOGIST S' ASS OCIATIO N J UBILEE VOL UME.

A . trivialis , A . s- piratis simus , Quenst , P enta crinus tu berculatus (abundant), and ilfontliva ltia (Thecocyatllus) rugosa (rather common near top). The Jam esoni-zone.-A small cutting some 15 ft. deep on th e Grea t Central Railway, near Wol fharncot e, exposed a brownish clay with ruddy nodu les, few fossils, and mu ch sele nite (peculiarly abse nt in all lower beds). This must be newer than the Armatus -zone and older than that of I bex , and so may be fairl y clas sed as j amesoni-zone. Mr. H . B. Woo dward* records A . jamesoni from about here, together with belemnites and Plicatula spin osa. The writer found in thi s section Gry pliaa cymbium, Leda suboualis , Pholad omya ambigua, W aldheimia numismalis, and ilf ontliualtia mu cronata , The j amesoni bed s were cut through on the Great Western R ai lway, near Fenny Compton, some years ago, but t wo or three zones are mixed up in Thoma s Beesley's record. t The Pettos-zone.-In a cutting of the Great Central R ailway, near Flecknoe, a clay of a light blue or grey colour was exposed, abounding in RlzyncllOnell a: (thousands could have been got from th e spoil bank). I t is clear th at this cla y is be low, alt hough not much below, th e Ibex- zone, and as it is so di stinct f rom the j amesoni-zone as any where else recorded the writer raised it to the rank of a zone. t The nodul es in thi s clay are exceedingly ab undant , but they are of the same light colour as the clay , never yellowish or ruddy like th ose in th e beds below, and never deep red like those in th e clays above, and th ey are very fossili­ ferou s. About sixty species of fossils occur, the on ly fairly common ammonite being A. pettos. On e nodu le with A . pettos conta ined also a young form of the Str iatus Group with well­ developed characteristics, which is probably A. bechei, Other fossils are: Ammonites oppeli, Belemnites clauatus, B. pollex (abu ndant), B. araris , Cardinia attenuata, Cypricard ia cua dlata, I noceramu s substriatus, ilfodiola scal-prum, Pecten cequiualois, R hyn cllonella variabilis, and Spirif erina uerrucosa,

A similar assembl age of fossils (but not th e Ammonite) W4 S recentl y sent to the writer from an ope ning near the canal and brickyard at Na pton-on-the-hill, and this makes it probab le that thi s zone corresponds to Upper [amesoni , and not Middle, as suggested in the pap er on th e Grea t Central R ailway j but th e exact position may still be regar ded as open to revision. The Ibex-zone.-This zone, so rarely to be recog nised in thi s

*

The Henleyi-zone.-This clay-zone is perhaps better iden­ tified by the absence of fossils than by the few that are found in it ; still , it is the special horizon, with us, of Ammonites henleyi, the young form of which is so like A. capricornus , which OCCurs abov e, and the old form to A. striatus, which occurs below, a peculiarly puzzling inversion of what might have been expected. There used to be a small br ickyard in this zone at Buckby Wharf, and the writer detected the zone in the cutti ngs of the Great Central R ailway near Wolfhamcote. None of the oth er few fossils are in any way cha rac teristic of the zone, and the clay is not distinguishable from the Ibex-zon e. Near Banbury the zone contains the stone bed which used to be got and poli shed , known as Banbury Marb le, and there it yields the large coral AIontlivalt ia victoria.

The Capricornus-zone.-Thi s zone differs from the last in that it conta ins numerous fossils, although the clays would .prob­ ab ly be indi stin guish abl e othe rwise. The zone has been exposed or identified at the following places :- nea r Banbury, in a brickyard, towards Middl eton Cheney j on the Great Central R ailway, near Catesby (visited by the Association in r896) j at Braunston, on the bank s of the cana l ; in a cutting of the Daven­ try to Leamington railw ay, near Braunston j in the mat erial from Kilsby Tunnel (togeth er with I bex and Henley: material) j at Little Bowden, near Market H arborough, etc. The best suite of fossils was obtained ' from the clays at the northern entrance to Catesby tunnel, of which a list is given in the account of the excursion in r896, t but by including other sections. the list could

• W oodward.H.B. Ge' l. Mag .. dec. 4. vo l, Iv ([897), p. 98. +P roc, CeDI. Assoc., vol. xiv, pp. 428-43°. 458 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. be increased somewhat. Chief fossils: Ammonites capricornus, A. jimbriatus (very large), Chemniteia transversa (abundant), Anomia numismalis (many), Avicula inaquiualuis (very abun­ dant), M odiola scalprum (fine specimens), and Opltioderma ( ?). A nearly complete list of the fossils found in the zones Semicostatus to Capricornus is given by the writer in "Geology of the Great Central Railway, Rugby to Catesby."*

MIDDLE LIAS.

There is a considerable change in the nature of the sediment on passing from the Capricornus-zone to the zone next above; moreover, the change is abrupt, and is accompanied by proofs of local denudation, so that for the district under review there can be no question that it is the best horizon on which to draw the line between Lower and Middle Lias. The Junction Bed between the stiff blue clays of the Lower Lias and the sandy, micaceous, blue or brown (according to porosity to water) clays of the Middle Lias consists of a layer of pebbles or water-worn nodules and fossils, mostly rolled. Some of the nodules are bored by a mollusc, and their surfaces may be more or less covered with serpulse, polyzoa, or foraminifera. A green sand is generally found around the nodules, and at one place, Watford, there was quite a bed of this green sand, and it yielded great numbers of foraminifera, t some thirty-five species altogether, of which two, Frondicularia rugosa C. and S. and F. delirata C. and S., were new. The bed has been detected at Catesby (in the tunnel), Wat­ ford, Cottesbrook, and Little Bowden. It can be well seen at the latter place now. Pecten cequivalvis occurs rather plentifully, but the most distinctive fossil appears to be a large plicatula­ Plicatula lavigata.

Nitescens, or Lower Margaritatus-zone.-The lower part of the Middle Lias 'consists of sandy, generally micaceous, clays of a blue or ruddy colour, depending upon circumstances, the latter being an oxidised condition of the former. This portion of the Middle Lias may vary in thickness from 60 to 80 ft., but the thickness appears to be inversely proportional to that of the higher beds of the Middle Lias, the total thick­ ness of the Middle Lias probably varying little from 100 ft. The geological maps require revising considerably to include these beds in the Middle Lias-they are mostly mapped as Lower Lias. In them there are irregular, indurated (cal-

" Quart, f ourn. Geot. Soc., vol. Iv (,Sgg), p. 65. j. Crick, W. D .. -H1d Sherborn, C. Davies, [ourn, Northam-ptonshi re Nat. Hist, 50,,°.; vol, vi. p. :::(.8 C: E OI .. . \ S S O l ·. J l "I :II .EE\.(),.. I · I. .\ T I-: X II r.

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To {t" ( /'d J.:.( -453. NORTHAMPTONSHIRE. 459 careous) masses, but by means of springs and well sections definite water-bearing beds from I to 2 ft. thick can be traced over a large area. Some or all of these thin beds contain rounded nodules, which look like real pebbles, and there is usually much iron in them. Portions of the beds have been exposed in the neighbourhood of Banbury, they have been en­ countered in various wells and borings, and can be seen at Crick and Little Bowden. They were seen in the Great Central Rail­ way cutting at the south end of Catesby tunnel. (See Plate XIII.) Undoubtedly Ammonites nitescens Y. and B. (A. algouianum Oppel.) is the characteristic ammonite (a form liable to be mis­ taken for A. valdani), but varieties of A. margaritatus are more common, and A. engelhardti (?) occurs even in the junction bed at the base as a water-worn fossil. Other fossils are: Turbo eyclostoma, Diseohelix aratus, Auicula ina:quivalvis (most abund­ ant), Pecten lunularis (abundant), Cypricardia eueullata (com­ mon), and Protoeardium truncatum (abundant).

Tile Upper Margaritatus-zone.-This zone is marked off from the one below, over a large area, by the occurrence at its base of a mottled rock, green with yellow inclusions, pebbles, water­ worn fossils, and comminuted shells. The thickness of the zone varies from about 40 ft. in the west of the county (Catesby and Badby) to about 20 ft. at Northampton. Stone beds occur at intervals, some or all of which yield water, according to the local porosity of the intervening beds. These thin stone beds are too much alike in fossil contents to be identified and traced with certainty by the fossils only, and their lithological character is very similar, but the interval between them is sufficiently regular to enable this to be done when the places are not too far apart (as in the case of the Niteseens-zone). There are no good sec­ tions of these beds to be seen now, only bits of them at places, though perhaps the best is in a lane at Staverton. Railway cut­ tings have several times exposed parts of them for a time, such as the London and North Western Railway near Watford Lodge, the East and West Junction Railway near Byfield, the Weedon to Leamington Railway a little beyond Daventry, and the Fern Hill cutting of the Great Central Railway branch from Morton Pinkney to Banbury. They have been cut through in many wells. Fossils are common enough, but none of special interest, as a rule, occur. Ammonites margaritatus is the only ammonite found, and this is not invariably common, although it may occur in any section. Protocardium truncatum is the ever­ present fossil. The most interesting bed the writer has come across in this zone was a hard bed, about 2t ft. thick, found immediately under, in fact joined on to the Middle Lias rock­ bed, at Daventry, in a railway cutting near the station. Car- 460 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. dinias were so abundant that it might have been called a Cardinia bed; these included Cardinia listeri var. hybrida, C. crassissima, C. crassiuscula, C. lapis, C. concimia, etc., also numerous gasteropods, including the two new species Trochus cricki (Wilson) and Amberlya eallipyge (Wilson).

The Spinatus-Zone is difficult to define; in some places, no doubt, it is merely the Middle Lias Rock-bed, the topmost bed of the Middle Lias proper, though it may include beds below in particular cases. The rock-bed is a thick ironstone in the south­ western parts of the county of Northampton, and is worked for iron near King's Sutton. In the same south-westerly parts of the county, where the rock is superficial, it has been largely used for building and road-making purposes. In Central N orthampton­ shire, around Northampton, for instance, where it is deep-seated and thinner, it is valued onlv as a source of water. This bed thins out both eastward and no;thward of South-West Northampton­ shire. The eastward attenuation appears to be due to real absence of sedimentation, as well as to local erosion, for beyond Wellingborough the rock-bed, where it can be recognised at ;11, is merely a layer of pebbles from a few inches to a foot thick. In a northerly direction, and particularly towards and at Market Harborough, change in character of the sediment rather than absence of the zone accounts for the apparent cessation of the rock-bed. Between these points intermediate conditions may be observed. The zonal Ammonite, A. spinatus, is much too rare to be of any practical use; moreover, A. margaritatus has not actually ceased to exist. The best guide appears to be the presence or absence of brachiopods. Rhynehonella tetrahedra and T'ere­ bratula punetata (and varieties) are entirely absent in the Upper 111argaritatus-zone, whereas they may be present in vast numbers in the rock-bed. At present the writer is disposed to believe that the occurrence of a single specimen of the above-named brachiopods on about this horizon may be regarded as fixing the zone in the area under review, though its absence must not be construed in the same rigid manner. Other fossils are: Belemnites p axiilosus (rather abundant), Pecten aquivalvis, Trigonia lingonensis, Spiriferina rostrata , Rhynchonella acuta , Terebratula walfordi, Waldheimia resupinata. The following list of localities where the Middle Lias Rock­ bed has been exposed will suffice nearly for the two, three, or four zones next above, a description of which is to follow, as these later zones are mostlv present more or less where the rock­ bed is worked: King's Sutton, Middleton Cheney, Thenford, Chalcombe, Edgcott, Chipping Warden, Appletree, Aston-Ie­ Wall, Byfield and around, Preston Capes, Catesby, Hellidon, near Arbury Hill, Badby, Bugbrook, Milton, Staverton, Dod- :,ORTHAMPTONSHIRE. ford, Floore, Daventry, Norton, Welton, Watford, Cottesbrook, Elkington, Market Harborough, etc., and in numerous wells and borings over a wider range.

Transition Bed: 'I'he Acutus-zone.-This zone, seldom more than a few inches thick, consists usually of a grey marl passing upwards into a red, sandy clay, and it is seldom absent where the rock-bed is found. The marl is the particular repository of the fossils, and in it are found a mixture of Middle and Upper Lias species; hence the term" Transition Bed" given to it by Mr. E. A. Walford. Ammonites acutus is most abundant, and.. although the bed is intimately associated with the rock-bed below, this ammonite never occurs in the latter rock, and perhaps never above the Transition Bed itself, though this is open to doubt. For this reason the term" Acutus-zone" was given to the bed by Mr. S. S. Buckman. Most of the Ammonites, however, are distinctly Upper Lias forms. About ISO species of fossils occur in the bed. Gasteropods are particularly numerous, and, on the whole, well preserved. Among other fossils are: Ammonites capiliatum, A. crassus, A. communis, A. annulatus, A. holandrei.

THE UPPER LIAS.

The writer has found it convenient to divide the Upper Lias' of Northamptonshire into eight subsidiary zones, or sets of beds, as shown in the typical section below.

TYPICAL SECTION OF UPPER LIAS. Approxi­ mate Name of Average Subsidiary Thickness Zone. Description of the Beds in ft. ]URENSIS ZONE IN PART (?). { Northampton Sand-lower part. I. UPPER LEDA OVUM { I. Layer of nodules, some bored, some 1 BEDS phosphatised . . • . . 13 LILLI BEDS (Buckman). 2. Micaceous sandy clay, with layers of to ]URENSIS ZONE IN nodules, oyster-beds, fossiliferous clay 24 PART (Thompson). balls, and characteristic fossils. .

II. 3. Oyster-bed, or Lima-bed. A layer Of} OYSTER-BED. bleached, water-worn nodules, often { covered with oysters, etc. . . . III. MIDDLE LEDA OVUM 4. Blue clay, with nodules. The chief I BEDS. BRAUNIANUS 6. ZONE IN PART. home of Leda ovum. Great abun- r3 (Thompson). l dance of belemnites ..••) 462 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

Approx ­ mate Name of Average Subsidiary Thickness. Zone. Description of the Beds. in ft. LOWER LEDAIV. OVUM { BEDS. CERITHIUM 5. Blue clay, with many ammonites and t 6 BEDS. BRAUNIANUS numerous gasteropods ... J 3 ZONE IN PART. (Thompson). V • UNFOSSILIFE~OUS BEDS \ 6. Blue clay, with large nodules, mUCh} (Judd). FIBULATUS ) nail-head spar in places, and very 76 ZONE (Thompson). , few fossils. .•... 7. UPPER CEPHALOPODA-BED. An Argil_} VI. laceous limestone, passing into hard COMMUNIS BEDS shale above and below; often oolitic. (J udd), SUBCARIN- Very numerous ammonites of the ATUS ZONE planulate group. 9 ins. to 18 ins. . (Thompson). { 8. Calcareous clay, with oolitic concre- tions and many small ammonites . 9· LOWER CEPHALOPODA-BED. A hard, 1 argillo-calcareous stone, with large VII. SERPENTINUS BEDS ammonites of the falcifer group; (1udd). FALCIFER r sometimes almost without fossils; J 4­ often more or less oolitic. About BEDS (Thompson). I l 6 ins. • . • • . . ,10. Light-coloured marl. Very few fossils II. INCONSTANT CEPHALOPODA-BED. A} hard shale, with numerous flattened VIII. ammonites of the falcifer group. FISH BEDS, or 4- ins. to I ft. . • . • • 2 LATESCENS ZONE 12. One or more bed. of hard, fissile (Thompson). { limestone, imbedded in a finely laminated shale, all with fish remains

184 In the above Table, Subsidiary zone I, beds 1 and 2 corre­ spond in part to the ]urensis-zone of other localities. Subsidiary zone II., bed 3, may be regarded as a transition bed. Subsidiary zones III. to VI., beds 4 to 8, correspond to the Communis­ zone. Subsidiary zones VII. and VIII., beds 9 to 12, corre­ .spond to the Serpentinus-zone of other localities. The name Communis-zone has no significance in Northamptonshire, since Ammonites communis is found well developed in the Transition­ Bed (Acutus-zone) below the Serpentinus-zone. Sections showing beds 6 to 12 have been visited by the Association at Bugbrook in 1891, and on the Great Central Railway in 1896. (See Proc . Geol, Assoc., vol. xii, p. 182, and vol. xiv, p. 425.) Fish Beds, or Latescens-zone.-There are several conditions of this set of beds. The most common is that of a single bed of laminated argillaceous limestone imbedded in a paper shale con­ taining, or originally containing, much organic matter. But the main bed may be only a line of lenticular limestone nodules, or NORTHAMPTONSHIRE. there may be two limestone bands and three shale beds. Both limestone and shale usually abound in fragmentary remains of small fishes. Another form of these beds is that of an irregular yellowish rock, quite unlike the typical form, and without paper shales, containing fewer fish fragments, but many more ammonites and other fossils. This abnormal form appears to be due to a coalescence of two sets of beds; hence the inclusion of the Inconstant Cephalopoda-bed (No. II typical section), and the naming of the group from an ammonite which links them together, but apparently is not found outside them, Ammonites latescens, Simp. A further intimate connection is suggested by many of the ammonites in the uppermost bed being flattened, as in the paper shales; and aptychi of ammonites being found in all these beds and no others of our Upper Lias. Other fossils are: Lepidotus elvensis, Pachycormus sp. (?), Leptolepis con­ centricus, Ammonites exaratus, A. frantei, A. strangwaysi, A. cornucopia, Beloteuthis (?) (these beds and no others), Cerithium subliassicum, Hud, and Wilson (typical), Euomphalus minutus (abundant), Inoceramus dubius (abundant). SECTION AT BUGBROOK. (Visited by the Association in 1891.) ft. in. COMMUNIS { BEDS, OR 1. Soil and blue clay, much disturbed, many small I 3 0 SUBCARINATUS ammonites of t.he planulate group ••• f ZONE. Z. LOWER CEPHALOPODA BED. An irregular layer 1 of small, weathered stones of a ruddy yellow 0 6 rALClFER colour. Oolitic in places. Nautilus, Ammonites, ( BEDS. J Nucula hammeri, etc. • . • . • ) 3. Blue clay, rather darker colour than usual. Red} and sandy at top, ruddy and shaly towards the 4- 6 \ bottom ; few fossils. •..•• 4· INCONSTANT CEPHALOPODA Bed. A hard'l bluish-grey stone. quite red at joints and ex- posed surfaces. Many ammonites of the falcifer \ group, very few of the planulate. Nautilus (0 8 astacoides (?) Aptychi of ammonites, A. exaratus, I A. stranguiaysi, etc. The fine-ribbed variety I of A. strangwaysi generally crushed. •. S. Paper Shale. A grey, finely laminated Shale,} weathering to a much lighter colour. Fish . FISH BEDS, fragments and flattened specimens of A. strang- 0 4 OR LATESCENS ways: ••.•.••. ZONE. 6. FIS I BED proper. A bluish-grey stone, laminated like the Shales, weathering quite white on theI exterior. Comes out in large flat slabs, only nodular in one part, and that just over a large 0 fissure in the rock-bed below. Fish fragments fairly abundant; only small ammonites, chiefly A latescens ; Saurian remains. ••• 7. Paper shale, like NO.5. A few ammonites and I Aptychi .•••• f 0 3 464 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

ft. in. 8. TRANSITION BED. Not present a. a distinct bed'l and no red clay; nevertheless clearly shown by ACUTUS ZONE. the altered character of the top of the rock-bed, j and by the presence here of Ammonites acutus, 5 0 A. annutatus, etc...... SPINATUS {g- ROCK BED of Middle Lias. An oolitic rock of a ZONE. greenish-grey colour internally, red at joints, with characteristic fossils. ...•

Serpentinus or Falcifer Beds.-These beds consist of a marl. with very few fossils, capped by a hard limestone band which, although fossils mayor may not be rare, is the particular home of very large specimens of Ammonites strangwaysi, a form which has often been quoted as A. serpentinus, Other fossils are: Ammonites subplanatus, Belemnites subtenuis, Amberlya capitanea (perhaps characteristic), Onustus spinosus, etc. Communis Beds, or Subcarinatus Zone.-This set of beds. consists of a clay irregular in composition, generally containing a large number of small, white concretions, and some larger nod­ ules. It contains immense numbers of small ammonites of the "communis" group. The clay is capped by a hard bed, perhaps shaly above and below, with abundance of ammonites lying at all angles with each other, and often pyritised, or where the bed is superficial oxidised to a good yellow or red colour. There is probably no bed in the whole of the Lias of this district, Upper, Middle, or Lower, which retains its character so well over large areas as this Upper Cephalopoda-bed. It is never absent from the sequence. At the majority of places where the Middle Lias Rock-bed has been quarried, these beds and all between may be seen. Ammonites subcarinatus is characteristic, though unfortu­ nately rather rare. Other fossils are: Ammonites communis (abundant), A. holandrei (abundant), A. semicelatus, A. bifrons (abundant), Trochus duplicatus, T. northamptonensis, Eucyclus acuminatus, Turbo theodori (all these four gasteropods appear to be characteristic), Nucula hammeri (abundant), N. clauiformis (characteristic). The Uufossiliferous Beds or Fibulatus-zone.-This set of beds has its lower limit in the Upper Cephalopoda-bed just described, and its upper where Leda ovum occurs. In them large nodules occur, some of which may be covered with or com­ posed of the so-called nail-head spar, or cone-in-cone j selenite is often abundant. Fossils are decidedly rare in the main mass. but towards the top and quite at the bottom a fair number may be found. Towards the top most of the ammonites are pyritised, and some are very large. The ammonite most likely to be found NORTHAMPTONSHIRE. often in batches, is A . flbu latus __ it does not occur below, but does pass into the L eda ovum Reds in the south-western part s of the county. The places where the zone has been found are too numerous to give in full, so only some of the sections to illustrate its distribu­ tion are mentioned ; CuIworth, near Morton Pinkney, Hinton Hill, Preston Capes, Brington, Long Buckb y, Holdenby, West H add on, Na seby, H ollowell , near Kelmarsh sta tion, near Clip­ stan station, Rothwell , K ettering (Northfi elds brickworks), Broughton, Wellingborough (pits near Midland Railway), Castle Ashby, etc. F ossils: Ammonites communis, A . bifrous, Ammonites of the subplanatus group , Nucula hammeri, Lucina bellona (perhaps the commonest fossil of main portion), P osidonomya bronni. L ower Leda ovum B eds , or Cerithium B eds: Braunianus­ zone (in part).-The cla ys of thi s zone are only to be distinguished from those below by their fossil contents. They are best identified by the abundance of Email gasteropods in them j Cerithium armatum being the chief. Ammonites braunianus is cha racteristic of these bed s and in diminishing numbers of the beds next above, and appears to be confined to them. These beds are, or have been, exposed wholly, or in part, at the following places; Thorpe Mand eville, Wappenham, East on Neston; Heyford, Bri ngton railway cutting, H unsbury Hill, Vigo, and Iresons pits at Northampton, Old H alf-way-house pit, Kin gsthorpe, Spratton, Well ingborough , H igham Ferrers, and in wells at various places. Vigo pit was visited by the Association in 1891 , and Rixon's pit,Wellingborough, in 1P94, though the latter chiefly exposes the beds below. Fossils are very numerous, hence the following is a much abbreviated list: Ammonites crassus, A. communis, A . subarmatus, A. heteropltyllus, A.lythensis , N autilus toarcensis , N. astacoides, Belemnites irregularis , Cerithium arntatum (and varieties), C. costellatum, Actaonina margin ata, A. decoratuni , Phasianella turbinata, Pecten pumilus (common), L ingula lougooiccnsis , Alatldlda crickii and Archccodiade ma th ompsoni , the two latter being peculiar to the zone and to Northamptonshire.

Middle L eda ovum B eds : Braunianus-eone in par t.-These beds are the chief home of L eda ourem, They are distinguished from those below by the absence of gasteropods, and are ter­ min ated above, mostly, by an oyster beef. With one possible exception not a single specimen of the genus Steplranoceras has been found above the oyster bed . One, or perhaps two, species of ammonites have been found in this zone and no other, but they are too rare to be of much use for identification of the zone ; they are allied to 11arpoceras / d lenbe rgi , Haug. Belrnenites 3° 466 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. are most abundant. The beds are found, generall y in association with another zone, at E ydon, E aston Neston, Northampton (all the brickyards, more or less), Kingsthorpe, Wellingborough, Earls Barton, Rushden, Irthlingborough; Kettering, Faxton near Lamport, The Association. has seen sections at Northamp­ ton rSo r, on the Great Central Railway in 1896, and Kettering Ig00 . There are few fossils of importance: Ammonites iythensis,A. similis ( ?), A . braunianus (not uncommon). No gasteropods have been found. A unique crustacean, P encus sllarpii Wood w., occur s. Oyster Bed.-Tb.is bed is of some importance, because, although the clay above it is like the Upper Lias clay below, and some of the fossils are common to both clays, nevertheless there is an assemblage of fossils in this th in bed and the clays above it totally unlike any found below. The bed consists of water­ worn, scratched, and bleached nodules, sometim es covered with oysters, at other times with serpulse, more rarely quite bare, but easily picked out from a heap with others by the colour. The stones may be entirely absent and only the oysters show, and in westerly parts of the county, where neither condition applies, the hori zon is sandy and the bed s above are thicker. F or list of sections see below. Fossils: Avicula ina:qu ivalvis, Lima toarcensis, Ostrea sandalina, O. subauricularis, Modiola gregaria, etc. Upper Leda 0 1JU m Beds: Lilli Beds (Buckman): [urensis­ zone (Thompson).-The clay s of this zone are about 13 ft. thi ck over a large area, but thicken in a westerly direction from North­ ampton. They are characterised by the presence of nodules or clay-balls crowded with fossils, or where these balls are absent by a particular suite of fossils which are important in connection with the identification of this zone with the ]urensis-zone of other localities. The bed is distinctly transitional as will be seen by the list of fossils, but the actua l assemblage of fossils seems unique. The layer of bored nodules at the top indicates a pause in sedimentation. The nodules thems elves are Upper Lias ones evidentl y, for they contain Ammon ites bifrons, but the fossil s on them may be Inferior Oolite ones in part, as the matrix sur ­ rounding them certa inly is in part, though there is also green sand similar to that usually found in simil ar situations (cf. junction of Capricornus and Nitescens-zcases, p. 458). Quite a large number of the more characteristic fossils of this zone are gregarious j they occur in bun ches. The localities in which this set of beds has been discovered have a wide range : Greens Norton near Towcester , Long Buckby, Harleston, Brixworth, Moulton, Northampton, Wilby, Welling­ borough, Finedon, Kettering, Desborough , Corby, Rockingham, NORTHAMPTONSHIRE. anci in wells at other places. Moulton was visited by the Associa­ tion in 1891, Corby in 1899, and Kettering in 1900. At the latter place the position and character of the oyster-bed was well seen. As this zone has given rise to much discussion (see Report of Excursion to Northampton in 189 I, Proc, Ceol. Assoc., vol. xii, pp . 172-19°), a rather fuller list of fossils is appended than seemed necessary for other beds: Ammonites bifrons (and peculiar varieties), A. elegans, Sow., A. subexaratus, Bon., A. IJlnpharum, A. aff. subplanatus, A. lythensis, A. similis ( 'I ), A. heterophyilus, A. iserensis, Oppel, A.(Lilli'.l) narbonensis, S Buckm., Belemnites crossotelus, B. ventralis, B. curtus, B. inornatus, Actaonina tumidula, A. pulla, A. Sedgvici, Cerithium muricatum, C. vetustum, Pur-purina sp., Pseudomelauia sim piex, P. procera (or near to), Turbo sp, nov., T'urrit ella quadrivittata. Astarte lurida, A vieula substriata, A. ina:quivalvis, A. miinstert, Cardium substriatulum (abundant), Cucullaa cancellata, Cress­ lya donaciformis, C. abducta, Lima toarcensis, L. duplicata, Modiola gregaria (abundant), Ostrea subauricularis , Pecten d emissus, P. cingulatus, Quenstedtia l a:vigata, Trigonia north­ amptonensis (characteri stic), U nicardi um stygis ( '!), V CllUS t enuis (abundant), Lingula beani, L. iongouicensis, Rl/yncltonella (two new species), T erebratula (two new species), and Eryma sp. (?) . The foraminifera are also peculiar to the beds, and one is new, Cristellaria opercula, Crick and Sherborn.

[unction Bed between Upper L ias and Inf erior Dolite.-It was long thought that the Upper Lias and Inferior Oolite of Northamptonshire were unconformable with each oth er and that there was a considerable time int erval between the formations unrepresented by strat a. The irr egular junction and apparent unconformity of the two has been shown in a series of papers* to be du e to sliding of one formation over the oth er on a hill-side, and to this kind of junction the term " false " has been given. In situati ons where this slipping could not have occurred, almost with out exception th e jun ction is regular and of the same special cha racter (" true junction ") ; the thickness of the Upper Lias below varies very slightly, and the upp ermost beds with their special fauna are present. The special character of the junction has on various occasions been pointed out when the Associati on happened to visit localities where Northampton Sand and under­ lying Upper Lias Clay could be seen in the same section. The junction bed in a "true junction" usually consists of a layer of characteristic nodules imbedded in a special matrix. The nodules are numerous and variable in size ; the small ones may be rounded, th e large ones are flat ; they may be light-

• BEEBY TH OMP SON: .. The Junction Beds of the U pne r L ia s and Inferior O olite!' [ ourn. N orthamptonshir» Nat. Hist, Soc., vols, ix, xi, xil, and xiil. 468 GEOLOGISTS' I\.SSOCIATION JUBILEE VOLUME. coloured (bleached) or they may be black, or of various colours between. Some are deeply scratched, others are pitted; many are bored by some boring mollusc, and they may be more or less covered with Serpulai, Polyzoa, etc. The matrix is cal­ careous, granular, apparently to a large extent composed of comminated shells of a grey to green colour, and highly phos­ phatic. Fossils found in the nodules: Ammonites bifrons, Lithodomus parasiticus, L. porteri, Modiola gregaria, etc. Fossils found on the nodules: Ostrea (sandaliua l ], T'crebra­ tula sp., Scrpula deplexa, S. trlcristata, S. tricarinata, Diasto­ pora stomatoporides, Nubccularia (?), and various Inferior Oolite forms. Fossils found with the nodules: Amongst certain well-known Inferior Oolite fossils are found: RhyncllOnella cynica, S. Buck­ man (?), R. aff. cyno cephala, T'ercbratula (near to circumdata Des!.), and some undescribed species, both of Rhynchonelia and Terebratula. With the exception of the first two, none of these brachiopods have so far been discovered in any other bed, locally, and Mr. S. S. Buckman thinks that the undescribed species are altogether new.

THE INFERIOR OoLITE. The Inferior Oolite of Northamptonshire is apparently incomplete; several zones have not been detected, but since by far the greater part is peculiarly free from ammonites of any kind-and this may mean associated fossils or groups-the exact correlation of the various beds is a problem which must be left for future solution. The following is a typical section of the Inferior Oolite Series in descending order: Apprcxi-. mate maximum NAME I)F SERIES. DEseRI PTION 010' BEDS. thickness in feet .. I. LINCOLNSHIRE LIMESTONE.-Cream-col­ oured freestones, shelly oolitic ragstones LINCOLNSHIRE ) and marls. Many fossils in places. •• So OOLITE. 'j 2. COLLYWESTON SLATE. - Fissile, calcar- I eous sandstones or sandy limestones, or , may be only sands.. •••• 5· 3. LOWER ESTUARINE BEDS.-:\'Iostly white or bluish sands with vertical plant markings. Some clay •... 4. VARIABLE Bzns.c-Calcareoue and slaty, NORTHAMPTON or soft sandstones. May incline to N os. 3 SAND. or 5 in character .•.•• 30 5. IRONSTONE BEDS.·-Rich red ore, ruddy sandstone, green or grey carbonate of iron, calcareous beds sometimes, and more rarely pyritous beds NORTHAMPTONSHIRE.

The NortllOmpton Sand is commonly spoken of as an Estuarine deposit j this is rather misleading, as the fossils in the Ironstone beds and the variable beds are all marine, and the lower beds are oolitic limestones in many places. The White Sands, however, contain plants that grew in stiti, and there are possibly some fresh-water or brackish-water shells in them j also there may be drift-wood anywhere in the series, and ripple­ marked surfaces occur in the sandstones of the variable beds. It seems likely, therefore, that the conditions changed from marine, through littoral to Estuarine. Ironstone Beds of tlte LVortlzampton Sand.-These beds con­ stitute a valuable source of iron, and they are worked at many places over a large area of the county. The red ore consists of the hydrated peroxide of iron-that is, Brown Hcematite or Limonite. It may vary much in appearance, but the most characteristic is that of a dark reddish-brown mineral, rich in iron, filling cracks in and coating blocks or roundish lumps of green, grey, or brown oolitic or other lighter-coloured ferru­ ginous matter concentrically, thereby producing a peculiar cellu­ lar or box-within-box-like arrangement. The green ore is almost entirely an oolitic carbonate of iron, to the colour of which either or both silicate and phosphate of iron contribute. Occasionally the lowest, bluish-green beds are rejected for furnace purposes because of the phosphorus they contain (Duston). These lowest beds are pyritous at certain places south-eastward of the outcrop. About 30 ft. is given as the maximum thickness, of the iron­ stone beds, but actually it is rare to find more than from 9 to r a ft. of good workable stone j 25ft. has been worked at the Duston ironstone quarries,. but this is exceptional. The per­ centage of iron varies very much in different kinds of stone, but 36 per cent. is about the average of workable stone. The origin of the iron in the Northampton Sand has engaged the attention of various geologists.* It appears fairly certain that the main mass of workable ironstone was once essentially an oolitic limestone, and the iron ore has resulted from the gradual replacement of lime by iron in the bed. The manner and time of the introcIuction of the iron, and the exact nature of the changes involved in the transformation, cannot be asserted with confidence, and the reader must he referred to the papers quoted below. The present chemical condition of the iron mainly as a hydrated peroxide can be accounted for by the passage of oxygenated water through the bed. The distribution of fossils in the ironstone heds is most erratic j in places they may be exceedingly abundant as casts '" MAW, G.: (Ian the Distribution of Iron in Variegated Strata," Quart. [ourn, Geol. Soc., vel. xxiv, p. 35r: JUDD, ]. \V.: If The Geology of Rutland," M'em, Geot, Survep j HUDLESTON, W. H.: "On tile Geological Historv of Iron- Ores," Prot. Geol. Assoc., vol, xi. p. 1C4. ~ 470 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. or moulds, and where the beds are more calcareous good speci­ mens can be secured, but miles of ironstone workings may be searched in vain for a good fossil. The lowest beds of the series are generally best for fossils, and from these a very considerable series has been obtained by taking advantage of suitable openings. The following are recorded by Mr. S. Sharp as not found elsewhere: Lima shar piana, Eth.; L. dustonensis, Eth.; L. deltoidea, Eth.; L. rodburgcnsis, Lycett M.S., a large Lima allied to L. grandis, Romer, and Trigonia sharpiana, Lye. A full list of ammonites is given, revised by Mr. S. S. Buck­ man, because of the interest attaching to it. An abbreviated list of other fossils only is appended. Ammonites: Lytoceras wrighti, S. Buckman (=A. [urensis, Ziet., auct.) ; Alocolytoceras taniatum, Pompeckj; Pachyly­ toccras aalentanum, S. Buck. j P. plzylloceratoides, S. Buck.; Lioceras aff. bifidatum, S. Buck.; L. nov. sp. aff. 'plicatelIum, S. Buck.; L. lineatum, S. Buck. j L. opalinum, Rein; L. opalinum, val'. comptoni, Rein; L. plectile, S. Buck.; L. thomp­ soni, S. Buck.; L. uncinatum, S. Buck.; L. sp. nov.; Hamma­ toceras sp. nov. aff'. Iorteti, Dum.; H. neiotoni ; S. Buck. (=A. insigne, Schub., auct.) , Hammatoceras sp.nov. (=A. corrugatus, auct. non. Sow. = A. murclnsona: val'. corru gatus of Sharp, non Sow.); Ludwigia murcliisona , Sow. (?); T'metoceras scissum, Benecke, Splza:roceras (?). Gasteropods are rare, but a good series has been obtained from one or two localities: N erinaa and Pseudomelania are per­ haps the commonest forms. Astarte elegans is a characteristic fossil, and other larnellibranchs likely to be met with are Ceromya bajociana, Gervillia hartmanni, Hinnites velatus, Limas of various species, Pecten personatus, Trigonias in the form of casts in iron are sometimes found by thousands in the ironstone beds. There is an interesting series of brachiopods, probably eight species of Rhynchonella, and ten of. T'erebratula, but the nomenclature wants revising and some are probably new. Corals are abundant in and around Northampton, but rare or entirely absent in other parts of the county. It would appear that in the lower part of the Northamp­ ton Sand there may be a mixture of the zones which in other districts are distinct, viz., the zones of A. jurensis (pars), A -. torulosus, A. opalinus, and A. murchisona, The only ammonite which probably does not occur in the lower beds is Tmetoceras scissum, judging by the matrix of the single specimen that has been found j. but Sharp speaks of .1. murchisona: as occurring tolerably high up.* A reference to the localities visited by the Association at various times will give a fair idea of the distribution of the iron­ ,~ SHARP, 5. , "The Oolit cs cf Northamptonshire," Qum't.j0tl1'11. Geol, Soc.; vel. xxvt, (,870), p. 354. NORTHAMPTONSH1RE. stone workings. Blisworth, Duston (near Northampton), and Lord Exeter's pits (near Stamford), in 1874; Brixworth, Stowe­ nine-Churches, and Duston in 1891; Wellingborough and Fine­ don, etc., in 1894; Corby, Weldon, and Gretton in 1899; Cran ford, \\roodford, etc., in 1900.

Variable Beds of tile Northampton Sand.-The variable beds are a distinctly local development, confined to Northampton and some few miles round. They deserve the name" variable," as within short distances they may be white or ruddy sands, red sandy freestones, hard slaty limestones, or irregular mixtures of all these. These beds must be looked upon as an addition to the nor­ mal sequence due directly and indirectly to coral growth within the area, that is to the actual addition of calcareous matter, and to the arrest of sediment of other kinds by the reefs. They are not represented in any of the extensive ironstone work­ ings in the county eastward of Northampton; in these latter the Lower Estuarine white sands rest directly on the ironstone beds. There are some fossils in these variable beds-indeed, por­ tions may consist largely of comminuted shells; still, a list from these beds only would be a small one and would contain nothing distinctive. Around Northampton these beds are to a large extent flaggy limestones, used for building purposes, and known as white pendle, They were seen by the Association at the Nursery Pit (Shittlewell Pit), near Kingsthorpe, in 1874 and 1891, the rock there being false-bedded and capped by rubbly ferruginous beds ; at Bass's Pit, near the race course, Northampton, in 1874 and 1891, where a good number of fossils have been obtained, including Rhynclzonella cynacephaia near the bottom. At New Duston the stone is largely a rich red freestone (sandstone), and has been extensively quarried for building purposes (visited in 189 I). Near here a certain portion of the series was at one time quarried for slates. -A deep sand-pit in Sandy Lane, to the west of Old Duston, must be largely on this horizon, although in lithological charac­ ter the rock approaches very nearly to the white sands usually found only above

The Lower Estuarine Beds, or White Sands.-These beds usually consist of pure white, light-purplish, or somewhat ruddy sands, with or without some argillaceous matter, though the sand is so fine that when wet it is almost like clay in its physical properties; when dry it may be very hard. Although usually so very distinct and sharply-defined from the ironstone beds below, this is not always the case, and work­ able ironstone may go right to the base of the Upper Estuarine 472 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. beds (see section below, visited by the Association in 1894), showing the intimate connection between the two sets of beds:

SECTION NEAR FINEDON. ft. in.

Soil and limestone, the latter in small flat pieces, largely crystalline, and highly fossiliferous. Ferruginous base, sharply separated from No.2. 4 10

2. Greenish grey clay, blue in places, with vertical plant markings I 10 3. Red sandy layer o 3 4. Variable bed-sand, clay, marl, and limestone, some of the latter hard blue-hearted stone. Where best to be examined as below :­ (a) Grey clay-no fossils c (b) Sandy marl-few fossils. •• c (c) Hard white layer-less sandy, more a} limestone, fossils abundant C.1'jJrina, Zouieana, C. "It/JtnSls, Cyn1la sp.? 2 c Cucullaa sp.?, P!acunopsis sp.?, Modio!a ,mbr,cafa, Ostrea sp. ? • • • • (d) Brown argillaceous limestone, white} towards base - many fossils; Ostrea o sowerbyi,o Modio!a imbricata, C.vprina, P!acunopsif socialis •. (e) Extremely variable layer, brown and) white, quite an oyster bed at base, t 6 Ostrea sonurbyi chiefly; Modio!a imbri- J cata •.•••••• 5. Blue clay crowded with oysters ; Ostrea souierbyi 6 [Unconformity-position of Lincolnshire Oolite.J 6. Irregular ruddy band. thickening to a bed here and} there as a stratified sand, by encroachment on bed next below. •••••. 7· Bluish grey sand, or sandy clay; vertical plant1 markings abundant in places. This bed varies r greatly in thickness, and in some places is quite o absent, from encroachment of the ironstone. Inf 4 places good rich ironstone goes tight up to the 1 base of bed 5 ••..•. 8. Ironstone of the usual form; some green layers of ) ( 10 c carbonate towards the base. Very undulating J to -/ upper surface for the reason assigned above. o t No fossils noticed ••...• 14 Beds (c) and (1) above no doubt represent the Upper Estuarine limestone. Some of the ironstone hereabouts gives over 43 per cent. metallic iron. A striking characteristic of these beels is the almost univer­ sal presence in them of vertical black streaks or even distinct NORTHAMPTONSHIRE. 473 carbonized stems of p lants of contemporaneous growth, probably a variety of cquisetnm. T wo distinct plant-beds may be di stin­ guished over many square miles (Stowe-nine-Ch urches and Corby, visited by the Association in 1891 and 1899 respectively), and at places (Corby) ho rizonta lly-bedded carbonaceous matter may be observed between the plant-beds, indicating contem­ poraneous denudati on. The sand, as such, is used for various purposes to a small extent only, being rather too fine for general use in building. Occasionally it is indurat ed enough to be used as a building stone (Kingsthorpe, visited in 1874), but it is not to be relied upon for resisting weatherin g, and its use for building is now entirely disconti nued. The clay-beds are used for br ick­ making at Dene (visited in 1899, see table on pa ge 474), and elsewhere, and terra-cotta manu facture at Stamford.

The Collyweston Slates are merely a local development of the lower part of the Lincolnshire Oolite. They consist of a hard, fine-grained, calcarea-arenaceous rock, having a striking resemblance to the Stonesfield Slat es. The rock is only now quarried at Easton and Collyweston (visited by th e Association in1906), but was at one time worked at Kirby and Dene Lodge (visit ed in 1899). The quarries at Collyweston have been worked in the sam e manner for upwards of 400 years , th at is to say, by " foxing," working und erground in " foxholes," though th ere are some open workin gs. There is only one bed yieldi ng slates, which var ies from 6 ins. to, in rare cases, 3 ft. in thi ckness, or its place may be entirely occupied by sand . The stone is got in th e early winter, and th en stacked on end in the open for the winter frosts to split it , along the planes of bedding; the dr essing being done in th e summer. It makes a pretty roof for stone-built buildin gs, but, of course, is rath er heavy. As already pointed out, th e horizon, instea d of being partl y san dy, may be wholl y so j as it is at Weldon, Dene, near Ketter­ ing, etc. (See table of Comparative Sections, p. 474.) The fossils inclu de : Teeth an d scal es of fish, th e character­ istic gasteropod Pterocera bentleyi, Gcruillia acuta , Cardium buckmani, Cucull aa cancellata, Avicula braamburiensis, 111odiola sowerbyana, Pinna cuneata, Trigonia pullus, and a unique star ­ fish Astra-pecten cotteswoldia: , val. stamfordensis, Wright.

The Lincolnshire Limcstolle.-This limestone, which is absent over western Northamptonshire, graduallycomes in as a sand bed, and attains a thickness of upwards of 80 ft. at Stamford, and of 200 ft. in Lincolnshire, hence the name Lincolnshire limestone or Lincoln shire Oolite. The lower beds of this form ation , above the slates, in Nortb­ amp tonshire are for th e most part marl y and soft, but occasionally 474 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. COMPARATIVE SECTIONS. CORBY. WELDON. DENE.

I Clay or Marl. Upper Estuarine Beds.

Oolitic 2 Limestone. Highly fossil- i iferous. .~ o"0 Weldon Stone. e Quarried for 20' ~

3 to " ~ ~ building "0 25' c purposes. <=: Limestone. Boulder Clay, ;J Lincolnshire Id A with chalk, flints, 3 Oolite. and scratched White, Red, and blocks. 4 Orange Sand, 5' Siliceous very variable. ,I concretions.

~,

Dark-blue Clay. Dark-blue Clay. Variegated 5 Sand, 4 irregularly '. stratified and White and Red Sand and Argill- false bedded. aceous Matter. 3' 6" 6 Sand. to Vertical plants. Vertical plants 4' 5 and iron pyrites. ~ White and Bluish-white 6 3' Dark Carbon- Dark Carbon- Sand. aceous Clay. aceous Clay. 3' Vertical plants. '1 No vertical Much wood. to 6' plants. No vertical Dark Carbon- plants. aceous Sandy '] Clay, 6' with wood. White and Red 4' Iron pyrites. White and Red to 8 Sand. " Kale." Vertical plants. Sand. 6' .. i" 8 Light-coloured Sandy Clay. 3' Ironstone, 10' Ironstone...... quarried for (Not in work). I 0' to 9 to? smelting. 12' Exposed to about 7 feet. I 2' Sandy Ironstone. 4'

" -._.~ Blue Clay. Ie Upper Lias .Ltlli-zone. Clay.

------

Blue Clay. Commums-zone. ~ Unconformity. NORTHAMPTONSHIRE. 415 appear as a nice cream-white stone formerly much used for domestic and church interior carved work. Higher beds form a good, rough, durable building stone. This is traversed in places by a shelly and partially crystalline bed, which at Stamford takes a good polish. It has been used for chimney-pieces, etc., under the name of Stamford Marble, and a similar stone occurs at Weldon. It is the upper beds that furnish the beautiful Ketton oolitic freestone (the quarries were visited in 1906), though this oolitic condition is continued downwards through a much greater thick­ ness at Weldon. The celebrated Barnack Rag occurs low down in the limestone series, and in this respect is abnormal. This stone, of which so many churches have been built, is a coarsely oolitic and shelly limestone, and is very durable. It was worked by the Romans, but the quarries ceased to be worked some 400 years ago. Some­ what similar, but thin, rag beds occur irregularly in the main mass of the limestone at Weldon and other places. The large stone quarries at Great Weldon (Weldon Stone) were visited by the Association in 1899; here, from 20 to 25 ft. is worked. A good deal has to be wasted, but the portion selected is of excellent quality for outside ornamental stone-work. Just outside Weldon, on the Stamford Road, there used to be a small roadside section of a loose or soft rag abounding in fossils, particularly gasteropods (cf. Hudleston's Monograph of the British Jurassic Gasteropoda. Pal. Soc.). This, if con­ solidated, would greatly resemble the Barnack Rag, but it is certainly fairly high in the series. (See table p. 414.) Other sections of Lincolnshire Oolite that have been seen during excursions of the Association are: Stanion (Lord Cardigan's pits), 1895; Simpson's quarry, north of Stamford, in 1814-a fine-grained oolite, very uniform in composition, which rings like a bell when struck. It makes a very good building stone, blocks of large size obtained; Tinkler's quarry-now the Stamford Lime Works-in 1874 and 19°6, chiefly the lower beds of the Lincolnshire Oolite. Here below a shale bed with crushed fossils, is a hard, blue-hearted limestone containing corals.. IVerinaa, etc .. the so-called Stamford Marble. Fossils are very irregularly disposed in the formation; the best oolitic building stone (Barnack Rag excepted) is remark­ ably free from fossils, but other beds are remarkably full, glvmg the impression of dead-shell banks. Ammonites are very scarce. the only two that have been quoted being A. murc hisonce and A. subradiatus, Other fossils are Natica leek­ lialllptoNensis, Pterocera bentleyi, Lucina wrighti, Pholadomya fidicula, P. zictcnii, Trigonia hemispherica, Cidaris fozolcri, C. wrigliti, T'crcbratula fimbria, RhyncllOnella spinosa, R. crossn , some good corals, and the plant Aroides stutterdi, 476 GEO LOGISTS' ASS OCIATI ON JUBILEE VOL UME.

THE GREATOOLITE. The following is a typical section of the Great Oolite, the beds being given in descending order: Approximate maximum DESCRIPTION 0 1,- BEDS. thickness. ft. I. CORNBRASH.- vVhite, ruddy, or blue limestone with many I IS fossils. •••..••.• f 2 . FOREST MARBLE SERIEs.-Variega ted clays, hard f1aggy , I 8 blue-hearted limestones, shale s, and oyster beds, etc. . f 3. G REAT O OLITE CLAY.-Blue and purple clay, with wood t 12 and car bonaceous matter, and ironstone . • • f 4. GREAT OOLITE LIMESTONE SERIES.- H ard, shelly lime- t stones in courses, with marly or oyster-bed partings • I 5. UPPER ESTUARINE SERIEs.-Very var iable .••\ ( a) Cla y or marl , g reen, gr ey, or blue, with vertical I plan t-mar kings and carbonaceous matter . . , (b) ESTUARINE LIMESTONE.-Hard, blue-hearted lime- l stone, or marl , with many fossils I to 5 or 6 ft. r 4° (c) Clay-black, blue, dark brown, or nearly whit e, I with vertical plant-markin gs and carbonaceo us ) matt er, or a n oyster bed. Ironstone at base .

Til e Upper E stuarine B eds rest upon the Lincolnshire Oolite where this is pr esent, and where it is absent upon th e Lower Estuarine beds. It is generally supposed that they are unconformable to the formation on which they rest, but the unconformity must be very slight. T he beds are so variable th at it is difficult to give in a few words a good description of them ; nearly every section is different. It is essentially an argillaceous series, with a f erruginous band at the ba se, which latter is sometimes highly fossiliferous. Over a large porti on of the county of Northampton it is capable of a three­ fold div ision (a, b, and c of typical section). T he dividing limestone ban d the writer has named the Estuarine Lim estone ; it is an important water-bearing bed in Mid- Northamptonshi re ; it may easily be mistak en for the Gr eat Oolite Limestone in pl aces, as it sometimes contains R hynchonella concinna in abundance. The Upper Estuarine series represents in tim e the Fuller's E arth of Gloucestershire and Somerset- indeed, the lime­ stone, 5b. may be a deposit contemporary with th e Fuller's Earth rock. T he upper part of sa, together with the lower part of the limestone above, probably correspond in time of deposition with the Stonesfield slate. T he clays are dug for brick-making (near Northampton, at Sta mford, etc. ) and have been used for fire-clay and terra­ cotta manu facture (Stamford). T he ironstone yields a good quality of iron, but it does not pay to work it. Agriculturally, the beds are probably th e worst in th e county, th e clays producing NORTHAMPTONSHIRE. 477 cold, wet lands, and the heartily-disliked oyster-bed soils locally known as pen-earth or penny-earth. There are few fossils of a distinctive character in the beds; the clay has yielded remains of the gigantic Cetiosaurus, and in the Stamford area occur two varieties of a characteristic bivalve, Neara ibbetsoni, Morris; also the brackish water bivalve Cyrena occurs at various horizons. Placunopsis socialis in some abundance is perhaps the best indication of the limestone bed.

SECTION AT WATKINS' BRICKYARD, HOPPING HILL, NEAR NORTHAMPTON. (Visited by the Association in 187-{and 1891.) ft. in. I. Soil. .• •• • t <> 2. Marl, very light coloured, with thin bands of a darker} coloured clay. Near the base some very thin bands 8 0 of limestone. Ostrea abundant .•.. Ii {3' Very hard limestone, blue-hearted, extremely fossil- / ~ ~ ~ ~~r~~s, ofb~c!o~:!en~~ :;und~~:n~~. th~f~::th~~~~ f z ') &l '" gj surface...... r.

Approx. ft. in. ,,; (1) Sandy layers, coarse shaly clay, and grey clay, with ;J{ numerous shells, also plants and wood. ..• 9 0 I>:Q:l (2) Variegated, dark blue, chocolate-coloured, purple, and ~ ~ yellow clay, with abundant carbonaceous matter. . 12 0 ""' Pl (3) Grey sandy clay, with exceedingly numerous and fine ~ ~ vertical plant markings. Red joints and streaks in the !-< lower part. ••...••• 6 0 ~ (4) Rich Ironstone, with a layer of gypsum on top • . o 9

No.2 is the best brick clay. NO.4 is evidently a bog iron ore, as there is much wood in it, and the layer of gypsum on top points the same way. The party of 1906 were able to see in one part of the quarry, in the top portion of the ironstone, part of a tree trunk about 6 ft. long and 3 ft. in circumferenoe, mostly converted into ironstone, but here and there showing structure. Various exposures of the two sets of Estuarine beds were seen between Kettering and Thrapston, where ironstone had been or was being got, in 1900. The Great Oolite Limestone consists of a blue, yellowish, or white limestone in various courses, the partings between the courses may be either sand, marl, dirty clay, oyster beds, or beds of comminuted shell. The rock is usually much jointed, some­ times can be obtained in large blocks, is rarely oolitic, and only occasionally can be worked as a freestone. It has been exten­ sively used for building purposes, where easily obtained, but it weathers so irregularly that in an old building kept in repair nearly as much mortar as stone is often to be seen; still, a vil­ lage built of the stone generally looks bright and tidy. The rock as a whole may be described as fossiliferous, but there are particular layers in it which are especially S0. Around Northampton such a layer exists near the base of the iormatioll; it is semi-crystalline, and abounds in N erincea, Astarte, Tri­ gonia, etc. It is generally called the" Nerinsea-bed." Towards Peterborough, around Castor and Alwalton, a hard, blue, shelly, subcrystalline limestone was formerly quarried, polished, and used under the name of Alwalton Marble, but it lacks durability. A hard, shelly limestone or ragstone found at Raunds and Stanwick was similarly used at one time. The section of hard, shelly limestone at St. Botolph's Bridge (Bottle­ bridge), near Peterborough, was visited by the Association in 1897, but not much was to be seen on that occasion. Rarely, the topmost bed consists of a marl with vertical plant-markings tcf, Stowe-Nine-Churches, page 481). NORTHAMPTONSHIRE. 479

~ _••._ ._••••4 Limestone quarries are fairlv common right across the county of Northampton on the out ­ crop of the formation, for although the stone is now little used for build­ ing, it is dug largely for ":'; lime burning, and in c; certain districts as a flux Y> for local iron smelting. '1 Fossils are common, Vl as already stated . The ...... ;'". following is a partial c list: T eeth , scales, '/, >. ." spines, etc., of H ybodus .,. dorsalis, H. grossiconus, ~ 3 ~ ::: Strophodus magnus, S. ::... 0 tenuis, Lschyodus sp. (? ), ~ ·r Cera to du s philtijJsii, ~ ~ Lepidotus unguiculatus, ~ "/. ...; Ophiopsis fleslteri, Aspi­ E";;. 0 dorhynchus sp. (?), 0 "~ ;.. jJf esod on bucklandi, lIf. , ~ rugu/osus. Ammonites '/, are very rare-A. gracilis. ~ o and another small species "~ C3 ::.: '/. occur; about a dozen 2: genera of gasteropod s ; ~ ~ man y lamellibranchs, of £' e, '" which Pinna am-pia is <:- /: characteristic. Br achio­ e . 0 '" ...; pods are abundant in , '" places, Rhync1lOllella '"~ ..,. concinna, Terebratula i1Z ­ -::- :..- "(3 termedia, and T . maxil­ '/, lata being of most com­ I mon occurrence. The YJ echinoderms include ~ '-' A cro sa/en ia C/ypeus ::~ ~'" mulled , and C. piotti, ._ ------~~ Eclzinobrissus, H olecty­ g pus , and the rare Ophiurella griesbacltii. Eryma elegans is com­ mon in places. Of pl ants, a cone of Pan­ danocarpum ooliticum, 480 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME.

Carruthers, is particularly interesting, and in the same bed where this occurred at Kingsthorp e is more commonly found the f ruit of a plant Carpolithes (Cy cadi nocarpus l ) , very like a nut . Corals are not uncommon. The Great Oolite limestone quarries near Bli sworth were visited in 1874. The ston e was then being worked for building stone, but now only for smelting-furnace purposes. The use of white limestone alternating with red ironstone in buildings at Blisworth was pointed out . On the same excursion the Moulton Park pits, near Kingsthorpe, were visited, where many of the commoner fossils were obtai ned, and the hard crystalline " Ne rinrea-bed " was observed . In 189 1 sections in the Great Oolite at Wootton and Roade, near Northampton, were visited. * On the same excursion Stowe-Nine-Churches was visited (see section post, p. 481), and in J900 a large section at Cranford St. John, which yiel ded a Rhynchonella, considered by the late Mr. J. F. Walker to be new.

Tlte Great Oolite Clay of J udd is the same as the Blisworth Clay of Sha rp, and no doub t represents, in time, the Bradford Clay of other localities. In Northamptonshire it is a vari e­ gated cla)'-blue, green , yellow, or purplish, and occasionally bituminous (Peterborough) . It contains in irregular layers or patches white, green , septa ria n, concretionary, calca reous, or ferruginous nodules, and often much wood or ca rbonaceous matter. There is generally a ferruginous bed at the base con­ taining concretionary ironstone nodules. At Stowe this bed also contains much selenite in curious interlacing laye rs, in these re­ spects much resemb ling the basement bed of th e Uppe r Estuarine Seri es at Stamford. Ostrea subrugulosa is fairly abundant, and as regards quantity maybe regarded as a characteristic species of fossil in differentiating this from the beds immed iately above­ the Forest Marble Series-when these latter are present. Blis­ worth (visited in 1874), Stowe-Nine-Churches (visited in J891 ), Thrapston, Is lip (visited in 190 0 ) , Oundle, and Wansford ar e some of the places where it has been well exposed.

The Forest Marble Series.-Over the greater part of North­ arnptonshire th ese beds are not indicated in any way. I n the north-eastern parts of the county they are usually inseparable from the Great Oolite Clay, hence, under the latter name a thickness of 20 ft. is record ed, but near P eterborough a hard rock occurs over a limit ed area. South of the Nene Valley, at Stowe­ Nin e-Churches, near P attishall. Reade, and Quinton, there are beds above the Great Oolite Clay which have very distin ctive characteristics, At Stowe th ey consist of vari egated clays ,

::';< Proc, Ccol, Assoc" vol. xii, p. 177. NORTHAMPTONSHIRE. greenish-looking at a distance, and containing wood and carbon­ aceous matter, with thin bands of fibrous carbonate of lime, hard shales, and fIaggy limestones, containing abundant interbedded plant-remains and many fossils, chiefly Ostrea. At Quinton and Roade a bed in the same position, and 3 or 4 ft. thick, consists almost entirely of Ostrea souierbyi, with a few specimens of lllodioia imbricata and Unicardium varicosum. Other fossils found at Stowe-nine-Churches are: Ostrea subrugulosa, Placunopsis socialis, Modiola leckenbyi, M. sub­ reniformis, Cardium stricklandi, etc. The section at Stowe was visited by the Association in 189I. The numbers and letters in the description are the same as in the photograph reproduced as Plate XIV, which, however, only shows the section down to bed 6. SECTlON AT STOWE-N1NE-CHURCHES: ft. in. ft. in. A. Soil with some Drift ... I o to 4 0 Position of small fault just shown in plate. ~~. ~ ,..,,.., B. Dark blue clay. No fossils I 5 0 ~~I,..,(.) :.:f%l 'f :z;o::, . {1. Fossiliferous limestone in two chief beds, upper ~ "'~ part rather red, lower nearly white, Ten- 0 0", S (.)

2. Variegated clay • ••• 4 0 3 to 0 ') 3· Hard, flaggy, blue-hearted limestone and shale, l .12~~,.., '" with Ostrea, wood, etc. Thin bed of fibrous J 6 ",0::", carbonate of lime near the top. •• "o

8. Light coloured marl, almost stone, with fine I <~o 2 9 ~~t; vertical plant markings .•.• f White limestone in numerous courses, many I ,,8~""~1 9· 25 o? fossils. . I .:J

'" z • w ~ gj 10" Calcareous clay. Only partly exposed. • 3 o? g; "~ P1 1II. Hard, shelly limestone. Only partly exposed 2 o? ::J \;;~ 12. Dark purple clay. Only lower part exposed . ? w ( ~f%lo ~ . I zO::f%l "'f-< 13· Ferruginous band, forming irregular junction} 5 12 8t::oO::1 1 to and 14 • • . • • • "'uQ Oz p....:J " 482 GEOLOGI STS' ASSOCIATI ON JUBILEE VOLUME.

ft. in. ~ {14' \Vhite sa nds, consis ting of an upper portion,} i:l ;;

Sui ~I

oz . .. II> '"II> ~ 16. Cellular irons tone and red sand, exp osed abo ut { 7 ° ;§~ ...... ~

The fallen blocks (C of Plate XIV.) are mostly Cornb rash . The section is interesting in several ways. It was worked for limestone, of which there is a fine bed, met with at different levels owing to faulting. The f aulting has preserved the most westerl y section of Cornbrash we have in the district, and the interesting Forest Marble Series. F our small f aults could be observed in the workings.

Tire Corn braslr.-This rock is a hard, blue, fossiliferous limestone when encountered under the Oxford Clay; when super­ ficial it weathers to a 'yell owish or ruddy colour, and forms a rubbly or brashy rock and soil supposed to be peculiarly suitable for corn growing. T he maps of th e Geologica l Survey show its distribution very well , but there are bits of it, outliers, at some other places (e.g . Stowe-Nine-Churches). The general thickness is about 5 f t., but at P eterborough it reaches 15 ft. The stone is not much used , though rough walling may be done with it, also road-mendin g, and it is occas iona lly burned for lime. Fossils are num erous. Remains of the fishes Strophodus magn us and S. teuuis, etc., occur. Ammonit es discus, A. macroce­ phalus, A laria trifida (?), and a few other gasteropods. Auicula echinata (abunda nt), P ccten vagal zs (abunda nt), Myacites (various species) , T'rigonia cassiopc, T. goldfussi , T . imp ressa , Ostrea flabell oides (abundant), Waldtreimia lagenalis (abundant ), W. obovata (abundant), H olecty pus depressus, E chinobrissus quad­ ratus, Anabacia complanata, etc . Sections of Cornbrash have been visited by the Association at Stowe-nine-Churches in 189I; a small outlier at Finedon Hill in 1894, at the Spital goods siding of the Great Northern Rail­ way at Peterborough in 1897 ; and at Islip and Thrapston in 1 9 0 0 . At the two latter plac es long faces of the rock a re ex­ posed, the workings being for the extract ion of the Great Oolite Lim estone below. ,;: l ~."' :..."" 'r: .~ :.:.:

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- ,--.- - .... ('I ..') N ORTJl AMPTONSHIRE.

MIDDLE O OLITES. T lte K cilmoays B eds within the County of Northampton are not often to be seen, and are not so distinctive as in the neigh­ bouring County of Bedford. About Raunds they consist of shales containing fissile, sandy layers almost pa ssing into stone, with Avicula inaqu iuaiuis , Gry p ha:a bil obata, and N ucula nuda.

T'he Oxford Cla.l'.-Patches of Oxford Clay may be found as outliers in various parts of the County of Northampton, and the formation is fairly continuous on the easterly margin of the county from Yardley Chase to P eterborough, but it is so often covered with Boulder Clay that exposures are few. The Boulder Cl ays of these districts are largely composed of Oxford Clay. The great Oxford Clay brick-making district of Fl etton , near P eterborough (just on the Huntingdonshire side of the Nene), was visited by the Associati on in 1897, and one of the several large pits from which Mr . Leeds has obtained so many fine vert ebrate fossils was examined. The best common fossils are usually obtained from the large septarian nodules, but the vertebrate skeletons occur on well -defined old floors in the clay, from whence they can be obtained al most entire. A very full list of the rept iles and fish that have been found in these pits will be found in the report of the excursion.*

THE GLACIAL DEPOSITS. The Glacial deposits of Northamptonshire will be treated very bri efly, partly because they have never received much attention from the Association 0 11 their visits to the county, and par tly because a revision of the usual interpreta tion of some of these deposits is necessary, and this is not th e place to enter int o a lengthy discussion of evid ence.

Pre-Glacial, or P reliminary Glacial Deposits.-There are certain deposits of sand and gravel occupying distinct elongated depressions which app ear to have been formed by strong cur­ rent s of water, aid ed by ice. T hey contain only local mat erial, no erratics whatever , and so are older than any tru e glacial deposits, and yet large boulders of earth with vegetation in them, in the lower part of the gravels, suggest ice action; and torrential water is indicated by the gravels themselves. Consequently preliminary glacial would seem to be an appropriate term for them. Exactly similar depo sits have been traced backwards to a higher level through Courteenhall (visited in 1891), Collingtree, Milton, Rothersthorpe, Bugbrook, H eyford , and on the northern side of

* Proc. Geol , Ass oc" vol. xv, p. 189. 484 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. the Nene valley as far as Ashby St. Legers. Thence they no doubt continue to Kilsby (tunnel) and on to Hillmorton (visited in 1898), at which latter place the sands are 170 ft. thick, and rest against a steep bank of Lias Clay.

Lower Boulder Clays and Sands.-The deposits just described appear to pass into the Hillmorton Sands, being connected therewith, perhaps, by comparatively narrow channels cut through the clay hills about Hillmorton, but since the Hillmor­ ton Sands pass gradually into the contorted sandy Boulder Clay of Rugby, another reason exists for describing the Courteenhall, etc., Sands as "preliminary glacial." This Lower Boulder Clay was well seen in the cuttings of the Great Central Railway in and close to Rugby, and from this and other evidence available it seems to occupy a kind of bay cut in the Rugby and Dunchurch plateau. This bed when wet has the physical properties of clay and can be moulded; when dry it is much more like a sand. It is really an irregular mixture of sand and clay, the sandy layers being sandwiched in with the clay. It is highly contorted, the contortions showing best when it is half dry, owing to the different hygroscopic capacities of the sand and clay. It is mostly very free from fossils or erratics, but in places it is chalky, and patches of gravel with erratics occur in other parts. The thickness of the deposit has not been determined. For further particulars about these Lower Glacial deposits see" Excursion to Hillmorton and Rugby," Proc. Geol: Assoc., vol. xv, p. 430; also "Geology of the Great Central Railway, Rugby to Catesby," Quart. [ourn, Geol. Soc., vol. lv, p.65·

Mid-Glacial Gravels and Sands.-The extensive gravel beds of the Rugby plateau are usually regarded as of mid-glacial age, and in all probability correctly so. At least they are of later age than the deposits we have just been considering, for they rest unconformably on the sands (at Hillmorton) and the con­ torted Boulder Clay and Lower Lias (at Rugby), but there is no Boulder Clay above to fix their intermediate age, and the fossils and erratics in them do not suffice for the purpose. Some eight miles farther south on the Great Central Railway there are some sands and gravels interposed between Lower Lias Clay and a red Boulder Clay. Extensive gravel beds occur in various parts of Northampton­ shire, which have usually been described as mid-glacial gravels, and some of them probably are such, but since the writer has been able to convince himself that some are not, he is now inclined to doubt all, unless confirmatory evidence is available. Some gravel pits on the side of a hill at Floore, visited by the Association in 1891, and always described as mid-glacial, NORTHAMPTONSHIRE. are obviousl y post-glacial, for when the hill itself, quite close, was pierced by a well a considerable th ickness of Cha lky Boulder Cl ay with insignifi cant gravel beds at its base was foun d. Also it is the rule rather th an the except ion to find Chalky Boulder Clay resting directly upon the local rocks without the interven­ tion of a grav el bed.

Early 1Vid-G lacial Gravels.-T he gravels occupy ing the d eeper parts of our valleys, below river level, are probably early mid-glacial , th e valleys having been cut out an d fille d in with gravel by th e great flood s result ing fro m the melting of the first ice sheet.

Late Mid-Glacial Gravels.-Besides the above there are what may be described as late mid -glacial gravels, gra vels formed by floods inaugurating the second glaciation. They occupy depressions of the nature of stream courses, an d are strikingly like th e beds at Courteenhall, etc., named Pre-glacial or Pre­ liminary glacial, but differ in two respects-they conta in small pebbles derived from an ea rlie r drift , and contain palseolithic implemen ts and remain s of the mamm oth. T hey are capped by chal ky Boulder Clay, and so cannot be confounde d with th e so-called river gravels. Ce rtain gravel beds mainly composed of local material ought, perhaps, to find a place here. At P ytchl ey th ere is a deposit of nearl y pure Grea t Oolite Limestone grave l, some IS ft. thick , covering a considerable area. Only a few quartz pebbles are present to fix it as a dr ift deposit. A very interesting section of redeposited Lincolnshire Oolite oc curs at Brigstock, and was visit ed by the Association in 1895. Here were found in the shelly oolite abundant fragments of recent shells, and preserved in clay a fe w that coul d be identified- Succinea putris , Cochlicopa lubrica, H elix pulcltella , H . nemoralis (or arbustorum), P upa marginate, Pisidium pusill um. Bits of flint and small pebbles could be foun d as far down as the sh ells extended and no farther. T here was Bould er Clay on top of all. For full er de scription of this section an d discussion on it, see II Peculiar Occurrence of Land an d Freshwater Shells in the Lincolnshire Oolite," Geol, ilfag. dec. 4, vol. ii, p. 223; also Proc, Geol. A ssoc., vol. xiv, p. 11 5.

Tlte Upper, or Cltalky Boulder Clar.-This wel1-knO\~n dep osit needs no particular description. It is abundantly dIS­ tributed over the county, sometimes attaining a thickness of 100 ft . The fossil contents vary in different parts, but judging by th e relat ive abunda nce of certa in fossils th e following is. the probable orde r of deriva tion of th e clay : Oxford Clay, Kime­ ridge Clay, Upper Li as, Middle Lias, Low er Lias. Chalk, 486 GEOLOGISTS' ASSOCIATION JUBILEE VOLUME. flint, Bunter pebbles, Carboniferous limestone, gritstone, and Coal-measure sandstone are fairly common erratics; mica-schist, granite, and greenstone are more rare. This chalky Boulder Clay has been seen by members of the Association at Blisworth in 1874, Corby in 1895 and 1899, and at various other places to a small extent over other rocks.

POST-GLACIAL AND RECENT.

The Post-Glacial Gravels.-As already explained, there is reason to believe that many of the gravel beds usually spoken of as mid-glacial are post-glaciaL There is one particular form of gravel in which chalk largely predominates and in which the sand even is largely chalk, that may with considerable proba­ bility be assigned to the post-glacial period, even where corroborative evidence is not available. The Valley Gravels, or River Gravels.-These deposits of sand and gravel, usually found' bordering the larger river valleys as terraces, occur along the Nene valley at heights varying from river level to 40 to 50 ft. above it. They consist chiefly of the contents of the former ice cap-that is to say, are essentially the residue of a washed Boulder Clay, containing flint and Bunter pebbles in great abundance; but they are more than this. As gravels they are of course post-glacial, but they contain a distinct fauna, which is not recent, and of which no trace is found in either the Lower or Upper Boulder Clay or in the post-glacial gravels occurring in other situations; therefore we are driven to the conclusion, which, after all, is the simplest, that the fauna is that of an inter-glacial alluvium of which the present gravels are in part a residue. Palseolithic implements also occur in these gravels, as in the mid-glacial ones. The terrestrial animals, remains of which are found in the river gravel, are Elephas antiquus, E. primigenius, Rhinoceros tichorItinus, Rhinoceros leptorhinus, Hippopotamus major, Equus caballus, E. priscus, Bos primigeuius, etc. In the upper part of the Nene valley, where the water-cur­ rents were strongest, only tusks and teeth, as a rule, are found; but lower down the valley, towards Peterborough, where sand largely replaces gravel, there is a mixture of marine shells, such as Cardium, with delicate fresh-water molluscs, as Physa, Planorbis, Limnaa, etc., and here, too, other parts of the skeletons of the larger animals referred to above may be found. Remains of the mammoth (Elepltas primigellius) are more abundant than any of the other species named, and quite a large number of molars were found in the extensive gravel beds near Elton. A fair number have been found at Northampton. NO RTHAMPTO NSHIRE.

The R iver Alluvium is a silt or sandy clay which has been deposited by flood-water since floods cease d to be of sufficie nt power to excavate. In age of form ation it is only a little newer tha n the river gravel with its much older f aun a, on which it partly reposes. The tendency of all floods now is to make the bottom of the valley 2. flat plane by depositing silt in the hollows. T he thickness of t he all uvium is very variable, as it should be, in virtue of its fun ction of a levell er. These clays generally contain a great deal of organic matt er, an d even large trees, the wood of which is quite black. The following plants were identified by Mr. H. N. Dixon and Mr. Clement Reid, by fruit or otherwise, in some alluvium at Mr. Martin's brickyard , near Northampton : oak, hazel (abundant), alder, common elder, pine (two species), bird-cherry, bla ck­ thorn, dog's mercu ry, knot grass (?), yellow water IiIy, and chickweed. Of anim als have been found: ox (both B os taurus var. longifrons and Bos tauru s var. primigenius), horse, sheep, wild hog, red deer, many specimens of recent fresh-water mol­ luscs, and some hum an remains, and remains of man's work, bur no stone impl ements. The bones often, and wood or stones sometimes, are of a bright-blue colour , du e to a coating of phosphate of iron (vivianite) on them. Wat er runn ing from the bed genera lly deposits a red sed iment, as it might be exp ected to do und er the circumstances.