The zones of the Oxford Clay near Peterborough

ZONES OF OXFORD CLAY NEAR PETERBOROUGH.

27

characterized much of the so-called stratigraphical literature of the last twenty years. No one wished to deny the presence of non-sequences. Many recent studies in sedimentary petrography had given significant emphasis both to the comparative rapidity of sedimentation and to the very spasmodic nature of the process. Better evidence, however, was needed for a nonsequence than the mere non-occurrence or non-discovery of a supposed zonal index. There were clearly the two possibilities, "strata failure" and " limited dispersal," and unless the supporters of the former could indicate decisive criteria whereby the two cases could be distinguished they had no resemblance of a right to deny the possibility of the latter. While in hearty agreement with most of Prof. Stamp's conclusions, it seemed to the speaker doubtful whether palaeogeographic maps could safely be taken as a guide to faunal provinces. Except in small regions like Britain, where detailed knowledge gave a desirable element of precision to such maps, restorations were largely based on supposed faunal provinces. There was thus a danger of begging the question in deducing faunal provinces from palaeogeographic maps. Mr. J. F. N. GREEN also spoke, and Mr. A. K. WELLS replied on behalf of the author.

THE ZONES OF THE OXFORD CLAY NEAR PETERBOROUGH, By E. NEAVERSON, D.Se., F.G.S., University of Liverpool.

Read March 6th., r925·

I

FIFTY years have now elapsed since the publication of the late Professor Judd's work,* containing an account of the Oxford Clay around Peterborough, and it is surprising that the exposures in the district have not hitherto been re-examined in the light of modern palseontological research. This work should obviously be taken up by a local geologist, since various parts of the sections are accessible at different times which do not often synchronise with rare visits paid to the localities by workers at a distance. The following notes, however, give some account of the broader sub-divisions of the Oxford Clay so far recognised in the district. The localities examined comprise three small areas indicated as Oxford Clay on the I-inch geological map (O.S. 64), viz. : (I) an area north of Peterborough, including Peakirk, Werrington, Dogsthorpe and Eye Green; (2) the district south of Peterborough around Woodstone, Fletton and Stanground; (3) the area around Whittlesey. Work on localities further south and south-east of Peterborough has had to be postponed to a future occasion. Many of the exposures described by Judd have long since disappeared, but modern brickfields enable the general sequence to be satisfactorily interpreted, though many details remain to be settled by future work. The exact limits of the zones, however, cannot be mapped owing to the cover of post-Pleistocene Fen deposits and the distances separating the exposures. • J. W. JUDD, Geology of Rutland, M em, Geol, Surv., 1875.

28

E . NEAVERSON, THE KELLAWAYS BEDS.

The beds immediately underlying the Oxford Clay show the lithological inconstancy usual in the Kellaways Beds throughout the country. These depo sits are exposed in a small bri ckfield north-west of the railway bridge near Werrington on th e main road to Pet erborough, where about 4 feet of dark-blue clay passes up into a thin band of soft concretionary sandsto ne covered by F en Gravels. The clay has yielded no fossils but the sandstone is prolific in individuals, though the number of species. is small. The most abundant fossils ar e grypheat e oysters which vary much in size an d in proportional ar ea of the attached surface of th e left v alve. One of th ese shells with a weak sulcus and feeble alar post erior expansion of the left valve is referred to Gryph cea bilobata J. de C. Sow., while others in wh ich these features are lacking are not specifically de termined . B elemnites oteeni Pratt, and Pt eria (Oxytoma) in equivaivis (J. Sow.) are common; P ecten (Syn cyclonema) demissus Phill. and P. (Chtamys) d. vagans J. de C. Sow. were also obtained. This fauna is distinct from th at of the Cornbrash and is similar to the assemblage obtained from the Kellaways Beds in other parts of the country, but, in the absence of ammonites, it s exact zonal position is unc ertain. It may be mentioned here that a small exposure of typical blu e-grey argill aceous limestone of the Corn brash occurs about a i mile to th e west , but on th e same side of the railw ay as the brickfield. Th e lim est one has yielded M acrocephalites sp. (frag ments seen), Pholadomya phillipsi Lyc., and Pl eurom ya securi[ormis Phill. The occurrence both of Kellaways Beds and Cornbrash at this locality appear s hitherto to have esca ped notice ; the latter is ab ou t !- mile eas t of the provisional boundary on t he r-inch geological map (O.S. 64) and emphasises the un certainty of mapping in a drift-covered area. A note on the petrography of the soft sandstone may be given her e. The most abundant of the heavy detrital minerals ar e garnet, tourmaline, zircon and rutile. The garnet occurs in rounded or angular, colourless grains (.08 to 0.2 mm . diam.), some of which show anomalous double refraction ; some grains exhibit re-entrant angl es consequent upon their sub-conchoidal fracture. The yellow-brown and grey-brown varieti es of tourmalin e in rounded prisms and irregular grains (.07 mm . to 0.1 mm.) are much more abundant than the blue variety. Colourless prisms and grains of zircon usually show signs of attrition ; some grains of this mineral are yellowish and others of a faint pink colour. The yellow variety of rutile is present in well-formed cry stals and twins as well as in angular fragments, but the foxy -red variety is not so common . Subangular clear grains of staurolite (0.1 mm.) pleochroic in yellows and ofte n showing

ZONES OF OXFORD CLAY NEAR PETERBOROUGH.

29

inclusions are frequent ; some fragments show the ragged edges due to weathering along the cleavage. Anatase is rare, out occurs in rounded yellow grains, some of which show a uniaxial negative interference-figure. Cleavage-flakes of muscovite {O.2 mm.), showing the usual characters, are generally larger than other mineral grains. Kyanite is not abundant, but occurs in small grains up to 0 .1 mm. diameter. Small yellowish grains of sphene are also present. Magnetite and ilmenite, the latter associated with leucoxene, are common. The light crop consists chiefly of subangular quartz grains, and occasional grains of a felspar with a refractive index slightly lower than that of Canada Balsam. The small number of mineral species in an abundant residue" and other characters of the grains (such as small size and degree of rounding) suggest that they were possibly derived from a preexisting sedimentary rock and not directly from an igneous or metamorphic massif. THE OXFORD CLAY.

As th e zonal nomenclature of the Upper Jurassic rocks is still incomplete, it is desirable to state here the general scheme used in the following pages. Th e left-hand column of the table below gives the zonal sequence to be discussed, and the older stratigraphical terms used by Judd ar e on the right . It may be noted that beds above the lamberti zone appar ently do not exte nd into the area described . ZONES.

lamberti athleta duncani castor coronatum elizabethre conlaxatum

f

JUDD 'S SEQUENCE

(I875).

Dark-blue clays with pyritic ammonites.

{

Clays with Belemnites hastatus , Clays with Belemnites oweni.

f

Clays with N ucula nuda and crushed ammonites. Kellaways Beds.

CON L A X A TUM Z 0 N E.-The lowest member of th e Oxford Clay at present known forms the floor of brickfields around Fletton, and also of workings at Kingsdyke on the main road from Peterborough to Whittlesey, about one mile west of the latter town. The clays thus situated are not favourable for examination, but numerous large septaria thrown out during the construction of shallow drainage-trenches are crowded with ammonites , many of which are uncrushed and in an excellent state of preservation. The sh ell is preserved, and the air chambers are filled with crystalline calcite, while the body-chamber contains

30

E. l-mAVERSON,

cement-stone similar to the mass of the septaria. Thus both the external features and the septal sutures may be studied. This ammonite fauna is of especial interest since it promises to enlarge our knowledge of the imperfectly-known group of Ammonites gulielmi J. Sow., which, until recently, was included in the comprehensive "genus" Cosmoceras (sensu lato). Speaking generally, the series contains forms which are highly ornamented, and others that show loss of sculpture correlated with a close approximation of the septa as growth proceeded. A highly-ornate, laterally-compressed species, with two rows of lateral tubercles, a smooth narrow venter bordered by two rows of short spines, and simple septal sutures with broad shallow lobes, is identical with Mr. S. S. Buckman's figure* of Gulielmiceras gztlielmi (J. Sow.). In this species, as growth proceeds, the two lateral tubercles fuse and form blunt radiating folds which proceed from the umbilical border. With loss of the lateroperipheral ribbing, the folds form the only ornament on another ammonite in which the periphery becomes rounded and narrowly arched; this form is apparently yet unfigured. Another ornate compressed species with simple suture-line is Gulielmites jason (Reinecke), which has recently been refigured by Mr. Buckman. t In this species, the outer nodes of the lateral area decline in strength and then disappear, while with further loss of sculpture, the derivatives of this ammonite have a practically smooth outer whorl, with narrow, rounded venterGulielmites conlaxatum S. Buckm. t Gulieimites delicaius. S. Buckm. a species recently figured§ from a German example, is also represented here; in this form the outer lateral nodes are obsolete and the venter is nearly smooth and bordered by small crowded nodes. Other forms, apparently undescribed, and differing from the above in various features, may be briefly mentioned here; they evidently belong to allied lineages in course of rapid evolution. A form with higher whorl-section than Gulielmites jason shows button-and-loop costation across the periphery, two ribs passing over the venter and uniting with a spine on each side; later, these disappear, leaving the venter smooth as in the previously mentioned species. Another ammonite is more inflated than all the others, the thickness of the whorl-section being about equal to the height; the greatest thickness occurs on the line of lateral tubercles in the middle of the lateral area. This specimen approaches in appearance the ammonites of the group of Cosmoceras spinosum (J. de C. Sow.) from the later duncani zone, but is easily distinguished by the form of the • s.

S.

BUCKMAN.

Typ, Ammonites, vel, iii, pl. CXCIV., 1920.

t Typ, Ammonites, vel. v., pl. DIll, 1924' tOp. cit., vol. iv., pI. CDXVllI., 1923. § Ot». cit., vol. v., pI, DXXI., 1924.

ZONES OF OXFORD CLAY NEAR PETERBOROUGH.

3£

ribbing. Each of the latero-peripheral ribs ends separately in a peripheral spine, while in the spinosum-gtoxu» two or three of these ribs coalesce with the spine forming a button-and-loop pattern. The ammonites occur in close association in the septaria, and are here referred to the Conlaxatum Zone, though Mr. Buckman has suggested a Gulielmi Zone for the reception of strata containing some of the ornate forms. The septarian band of this district is apparently the condensed representative of strata which in other districts have been referred to the Kellawavs Beds. * The occurrence of G. gulielmi in the Kellaways Rock of Wiltshire emphasises the lithological inconstancy of the basal part of the Oxford Clay in various parts of the country. Other fossils obtained from the septaria are Belemnites oweni Pratt, Aptychus sp., and an incomplete specimen of Spinigera. The latter seems not to agree with a shell described by Dr. F. L. Kitchin] from the Oxford Clay of the Kent Borings; it has a highly-elevated spire and the whorls bear two major longitudinal ridges separated by a slightly concave striated valley, while the shoulder bears finer spiral ridges. The Kent fossil, moreover, appears to be slightly later in age, viz., "near the top of the Ornatus subdivision." ELI Z ABE T H ,£ Z 0 N E.-Above the septarian band just described there is a considerable thickness of shales which contain innumerable fossils with shell preserved but mostly in a crushed condition. They are similar in preservation to the wellknown series obtained many years ago from a railway-cutting at Christian Malford (Wilts.). The ammonites from the latter locality, which were originally described by Pratt.j are now being refigured by Mr. S. S. Buckman, and many of the species are closely comparable with those found in brickfields around Peterborough. Those collected by the writer are listed below, reference to Mr. Buckman's figures in " Type Ammonites" being given in square brackets. Hoplikosmokeras fibuliferum S. Buckm. [T.A., vol. v., No. 4 89, 19 24·J H. sp. d. hoplistes S. Buckm. [T.A., vol. v., No. 488, 19 24·J H. pha'mmn S. Buckm. [T.A., vol. v., No. 490, 1924.J Spinikosmokeras aft. acutistriaium (Robson). [T.A., vol. v., No. 486, 1924.J S. aft. pollux (Reinecke). [T.A., vol. v., No. 487, 1924.J The list is far from complete owing partly to the fragile nature * G. \V. LAMPLUGH, F. L. KITCHIN, and ]. PRINGLE . . . The Concealed Mesozoic Rocl.s in Kent, p. 72, M em. Geot, Suro., 1923. t Ibid, p, III.; t s. P. PRATT, Ann, Mag. Nat. Hist., vol, viii., pp, 161-165, 1842.

32

E. NEAVEI{SON,

of the fossils, some specimens becoming hopelessly broken during transit from the brickfields, Other fossils collected from this zone include Belemnoteuthis sp., Belemnites oieeni Pratt, Gryphcea sp., a species of Nucula usually identified as N. nuda Phill., and Cerithiuni d. muricatum Sow. The shales have also yielded well-preserved fishes and the late A. N. Leeds obtained many fine skeletons of reptiles. Though Mr. Buckman has suggested several subdivisions of the Elizabethse Zone based on the development of the ammonites, these cannot at present be stratigraphically defined in our district, but the fine series of excavations will probably afford the means of testing the efficacy of such detail. Sections of the Elizabethse Shales are to be seen in brickfields around Fletton, in the group of workings at Kingsdyke (about one mile west of Whittlesey), and also in a brickpit J mile east of Dogsthorpe. COR 0 NAT U M Z 0 N E.-The only substantial evidence obtained for the presence of this zone is the occurrence of large specimens of Erymnoceras reginaldi (Morris) in Messrs. Itter's brickyard It miles west of Whittlesey. The specimens occur in shales similar to those of the Elizabethze Zone but were not in situ and the position of the zone in the section could not be located. A poor fragment from similar shale at Fletton is also referred to this species and doubtless further work will fully establish the presence of the Coronatum Zone throughout the area covered by these shales. By the use of suitable solutions for hardening the specimens before transport good examples might be preserved: one such ammonite from Whittlesey is now in the collection of the University of Liverpool. Belemnites oweni Pratt, and the lamellibranchs of the Elizabethse Zone persist into the Coronatum Zone. Especial mention may be made of the presence of Grammatodon montaneyensis (de Lor.) which, though it appears to have a long vertical range and wide horizontal distribution, is not well-known in this country. CAS TOR Z 0 N E.-In Bavaria, the beds between the Coronatum Zone and the higher Ornatum Beds contain a wellmarked ammonite-fauna which is apparently unknown in England, and the strata around Peterborough, occupying a corresponding position, are deficient in ammonites. Judd recognised two horizons here, viz., a lower" Clays with Belemnites oteeni," and an upper" Clays with Belemnites hastatus." These divisions seem to have little significance, since Belemnites oweni is abundant throughout the lower zones just described, and Belemnites hastatus appears to have a long vertical range in the upper zones. Associated with Belemnites hastatus in these clays are Serpula vertebralis Sow., Anabacia complanata Auctt., Pecten (Chlamys) d. fibrosus J. Sow.; a dwarf, or immature specimen of Acrosa

33

ZO:-lES OF OXFORD CLAY NEAR PETER BOROUGH.

lenia was also found. Clays of this horizon (together with lower beds), ar e worked in pits around Fletton and west of Whittlesey, while Judd recorded brickfields (now filled in) at Werrington. In a pit adjoining the railway station at Eye Green the lower zones of the Oxford Clay (including the Castor Zone) are faulted against higher zones-judging by fossils obtained from the upper surface of the clay where the overlying Fen deposits had been removed, as well as by the sections. The north side of the pit shows the Duncani, Athleta and Lamberti Zones, while the south side (not now worked) is in clays of Elizabethre and Castor age. Thus the fault has approximately an E.-W. direction and is probably a continuation of the fault mapped further west by the officers of the Geological Survey.

DUN CAN I Z 0 N E.-The clays of this horizon are worked at Eye Green brickfield and yield an abundance of ammonites preserved as pyritic casts, the most characteristic of which are species of Cosmoceras (s. str.). An ammonite which appears to be an early development of the series is Cosmoceras spinosum (J . de C. Sow.). This species has a somewhat depressed whorlsection; it bears a single row of tubercles on the lateral area and a double row bordering the periphery; button-and-loop costation extends betw een the lateral and peripheral tubercles but does not cross the venter, which is smooth and feebly sulcate. This and allied forms are the most evolute ammonites of the Duncani fauna, the width of the umbilicus reaching 40 per cent. of the diameter. A form similar to C. spinosum, but with a somewhat compressed whorl-section is probably C. gemmatum (Phill .) The evolut e ammonites just described develop into laterally compressed form s with high whorl-section and a double row of transverse bullee on the sides ; these may be recorded here as Cosmoceras d . pronie Teisseyre. In other forms the double row of lat eral tubercles becomes obsolete and the venter undergoes flattening with approximation of the nod es; later (in some specimens) the periphery becomes rounded and broadly arched. Such ammonites have long been known as Cosmoceras [ason (Reinecke), a form which has been interpreted differently by many authors. As stated abov e, Mr. Buckman has recently figured a chorotype of Reinecke' s species and refers it to a considerably lower horizon (th e Conlaxatum Zone) which form s the base of th e Oxford Clay in our district. Consequentl y the name " Cosmoceras [ason " does not occur in our list from th e Duncani Zone. One of these late developm ents of Cosmoceras is very near C. rimosum (Quenstedt). but the series is difficult to separate into species. Probably two or more rapidly evolving lineages ar e repre sented, and these ma y be conn ect ed by interbreeding. Several specimens of Lun uloceras d. n odosum Bonarelli, and a single ammonite ascribed t o S iemiradzki a plana (Siem.) were PROC. GEOL. Assoc., VOL. XXXVI., Part I , 19::5·

3

34

E. NEAVERSON,

obtained from the spoil-heap at Eye Green and probably belong to the Duncani fauna. Some pyritised casts of bivalves (also from the spoil heap) include Nuculana d. phillipsi Morris, other species of Nuculana which are perhaps comparable with N. longiuscula (Merian) and N. cottaldi de Lor., a Cucullaea which nearly approaches C. subtetragona (Morris), and a cast that is doubtfully referred to Lucina. Two gastropod casts are assigned to the genus Pleurotomaria ; one has a more elevated spire than the other, but neither can be specifically identified. AT H LET A Z 0 N E.-The clays above the Duncani Zone contain as their most abundant fossil, a large grypheate oyster with a comparatively small area of umbonal attachment. This form is usually recorded as Gryphcea dilatata ]. Sow., but much detailed work is needed on the various ostrean lineages which develop the grypheate habit before these forms can be definitely determined. These shells are abundant in brickfields near the railway stations at Eye Green and Whittlesey. At the former locality Aulacothyris bernardina (d. Orb.) is frequently found. At both localities large Peltocerates (up to 10 inches in diameter), occur together with small specimens in the costate stage. These ammonites attain the tuberculate condition comparatively early, when the venter becomes wide and flat and is crossed by strong ribs in groups of three, each group uniting with a tubercle on either side. At a later stage the peripheral ribs decline in strength and the venter becomes smooth in the largest specimens observed. These ammonites are referred to Peltoceras athleta (Phill.). A Peltoceras picked up loose at Eye Green is probably another form since it is still costate (and fully septate) at a diameter of 75 mm., with a higher whorl-section. LAM B E R T I Z 0 N E.-The clays at the top of the section at Eye Green fall into the Renggeri Zone, as described by Professor A. Morley Davies* and Dr. F. L. Kitchin], for Buckinghamshire and Kent respectively. These authors regarded the available evidence as insufficient to establish the suggestions of Mr. S. S. Buckmanj that a Lamberti Zone could be distinguished at the base of the broader subdivision, although Dr. Kitchin was able to show that the fauna of this horizon was not the typical renggeri assemblage. Prof. A. M. Davies compared the renggeri fauna of Bucks with that of the Swiss Jura where the zone is typically developed. The main feature of the Buckinghamshire fauna is the presence of abundant ammonites belonging to the genera Quenstedtoceras, Hecticoceras and Creniceras, while Cosmocerates are absent. • Zones of the Oxford and Ampthill Clays in Bucks and Beds, Goal. Mag., vol. liii, p. 396, 1916• t G. W. LAMPLUGH. F. L. KITCHIN and J. PRINGLE. op. c;t., p. 210, 1923. : Qua,. Jour». Geol, Soc., vel, lxix., p, 159, 1913.

ZONES OF OXFORD CLAY NEAR PETERBOROUGH.

35

Compared with the large series of forms obtained from Bucks, the fauna from Eye Green presents interesting differences : 1. The species of Quenstedtoeeras are few in number and are forms with comparatively coarse ribbing and feeble rostration such as Q. lamberti (Sow.), Q. cf leaehi (Sow.), and Q. d. goliathus. (d'Orb.). The fauna from Bucks includes many forms with finer ribbing and accentuated rostration; these have not so far been collected at Eye Green. 2. While examples of Heetieoeeras, such as H. hecticus Qu. and H. girodi Bonarelli are common in both areas, Crenieeras and Tarameliiceras are not yet recorded from exposures in our district, though they were found in Bucks. The evidence obtained at Eye Green thus corresponds closely with Dr. Kitchin's record from the Kent borings and is now deemed sufficient to confirm the establishment of the Lamberti Zone as suggested by Mr. Buckman. Ammonites comparable, but not identical with Perisphinctes subtilis (Neum.) and" P." bernensis de Lor. were collected on the spoil-heap at Eye Green and may also belong to the Lamberti Zone. Bivalves appear to be less plentiful than in the underlying beds and no specimens were collected in situ. GENERAL CONSIDERATIONS.

The above observations indicate that the Oxford Clay around Peterborough shows a normal sequence from the Kellaways Beds to the Lamberti Zone. The Renggeri Zone apparently does not extend into the area described, though, further south, its ammonites are recorded by Judd* from brickfields south of Ramsey Mere, and by Roberts'[ from St. Ives, where Ampthill Clay also is mentioned by Dr. L. F. Spath.] In the northern part of the district the limit of the Cornbrash is displaced westward by faulting to a distance of about four miles, as indicated on the r-inch geological map (O.S. 64). Judd has recorded Kellaways Beds at Dogsthorpe (south of the fault), and their occurrence N.W. of Werrington (north of the fault) is described in this paper. Judd also records" clays with Belemnites hastatus," (? Castor Zone) east of Werrington, but the brickfields have long since disappeared. This fault has now been recognised at Eye Green (as mentioned above, p. 33), where beds containing the lamberti fauna are brought into juxtaposition with Beds here referred to the Castor Zone. South of the fault, the Lamberti and Duncani Zones have not been traced by the writer, but Judd records ammonites indicating the former zone from Eastrea (east of Whittlesey), and ammonites of the" Ornatus • Op, cit., p. 237. 1875. t The Jurassic Rocks of the Neighbourhood of Cambridge, Sedgwick Prize Essay for 1886. p. 17. 1892. t Qua,. J ou,n. Geol; Soc., vol. Ixix., p. 579, '9'3.

E . NEAVERSON,

group" [? Duncani fauna] from" the large clay-pits at Whittlesey" and from Thomey. These records and observations are all in general agre ement with the existence' of a fault across the district with a northerly down throw roughly estimat ed at 40 to 50 feet. The delimitation of the zones in the Oxford Clay should aid the solution of some inte resting local problems concerning the geological structure of the district south of the Wash. The floor of the Fenland under the drift is doubtless form ed largely of Oxford Clay, but at some places, as at March and Chatteris, the presence of Kimmeridge Clay forming" islands or in the Fens is recorded . Most of these records ar e ancient and must be regarded with due reser ve, since critical palseontological work is still in its infancy. Unfortunately, in most cases, the recorded fossils are not preserved or their whereabouts is no t known. This, coupled with the disappearance of exposur es, adds to the difficulty of correlating deposits largely concealed by Drift, in an agricultural district. Thus, at March, where Kimmeridge Clay is recorded, there is now no exposure, and the only Kimmeridgian fossils from that locality of which the writer is aware are specimens (in Wisb ech Museum) , of large Ameebocerates that are elsewhere in the Midlands only obtained from the Kimmeridgic Boulder Clay . A boring at March in 1883 is interpret ed by previous writers* as follows: 1 2 feet Made ground and shelly gravel Kimmeridge Clay 58 " Oxford Clay ... 214 " .. Ammonites bi-plex " and .. A. cordatus " are recorded from a depth of IS feet in the so-called Kimmeridge Clay, but doubt is expressed concerning the determination of these ammonites. t In the absence of specimens no cer tainty can be attained, but the opinion may be advanced that the presence of a cordatus-like ammonit e dates the beds as not younger than Lower Coralli an. Indeed , many specimens in Museum collections are still labelled .. A . cordatus," though they obviously belong t o the Renggeri Zone of t he Oxford Clay. The " biplex " ammonite may also be earlie r th an Kimmeridgian , since similar forms are known from the Oxford an d Ampthill Clays. Indeed , the type P erisphin ctes biplex (Sow.) is an Argovian form . Thus considerable unc ertainty surrounds the recorded occur rence of Kimmeridge Clay at March, since the majority of Ammonites from the form er brickfields (only 40 feet deep) are Oxford Clay forms, and later ammonit es occur plentifully in the Glacial Drift. Also, March • t w. WIlITAKE R , S. B . J. S KE R TCH L Y a nd A. J . J U KES- B RO WNE , Geology of and of N. Cambridgeshire (Ex pl. of Sheet 65), p. 154. Mem . Geol, Surv ., 1893.

S .W .

Norfolk

GEOLOGY OF THE WHITEHAVEN DISTRICT.

37

and Chatteris are on the line of presumed strike of the upper renggeri beds. As Mr. Pringle implies, * the recent observation at a boring at Long Sutton (16 miles north of March) of Upper Oxford Clay and Lower Ampthill Clay directly underlying the Boulder Clay further supports the idea that the western boundary of the Kimmeridge Clay is to be found east of the " March Island." As Long Sutton is north of the fault by which the beds are displaced westwards the above occurrence is regarded as especially significant. In conclusion, the writer wishes to record his indebtedness to the managers of the various brickfields around Peterborough for facilities (readily granted) to examine the sections; also to Professor P. G. H. Boswell for verifying the determination ·of the detrital minerals from the Kellaways Beds of Werrington.

A SKETCH OF THE GEOLOGY OF THE WHITEHAVEN DISTRICT. \By BERNARD SMITH, M.A., Sc.D.; E. E. L. DIXON, A.R.C.Se., B.Se.; T. EASTWOOD, A.R.C.Se. ; C. EDMONDS; and S. E. HOLLINGWORTH, B.A., B.Se.

THEof the Whitehaven district, situated on the western flank main Lake District massif, offers problems in geology

quite as interesting as, if differing in type from, those of the much better known and more frequented Lake District proper. This western plain (as distinct from the Fells) is diversified and exhibits strong variations in relief. It is trenched by several important valleys and its coast scenery in places attains grandeur. Near Dean Moor and Arlecdon it rises to about 700 feet above sea-level, but the general average is nearer 400 feet. St. Bees Headland reaches its highest point in Hannah Moor, west of Rottington, at 466 feet O.D. The most remarkable physiographical feature, perhaps, is the St. Bees-Whitehaven gap, traversed by the Furness Railway, which isolates St. Bees Headland, known as Preston Isle, from the rest of the plain, as a low-level through valley which, if drowned, might be compared with the Solent or the Menai Straits. From Cockermouth to Ennerdale the western margin of the Fell country occurs as a nearly north-and-south line; south of Ennerdale, however, it swings westward for several miles to Dent, and then southward to the neighbourhood of Egremont. Thereafter it runs eastward and south-south-eastward past Gosforth. To the north the combined Derwent and Cocker enter the sea at Workington, whilst the Ehen, issuing from Ennerdale • Summary of Progress for

1921,

p.

III,

Aletn. Geol, Sun'., 1922.