a synopsis of the jurassic rocks of yorkshire

247

A SYNOPSIS OF THE JURASSIC ROCKS OFYORKSHIRE.

By VEHNON WILSO:-<, Ph.D., B.Se., D.LC., F.G.S., .T. E. HEMlI\GWAY, Ph.D., B.Se.,and MAGRICE BLACK, PIr.D., M.A., F.G.S.

[WriUm for the Summer Field Muting; 1934]

CONTENTS.PAGE.

1. INTRODUCTION. By Vernon Wilson, Ph.D., B.Sc., D.LC.,F.G.S. 248

II. THE LIAS OF THE YORKSHIRE COAST. By J. E. Hemingway,Ph.D., B.Sc. 250

III. THE MIDDLE JURASSIC ROCKS. By Maurice Black, Ph.D.,M.A., F.G.S. 261

IV. Tms CORNBRASlI AND UPPER JURASSIC ROCKS. By VernonWilson. Ph.D., n.se.. D.Le., F.G.S. 274

V. SUMMARY. By Vernon Wilson, Ph.D., B.Sc., D.LC., F.G.S. 288

V1. SELECTED BlBLI'OGRAPHY

PROC. GEOL. Assoc .• \'01.. XLV., PART 3. 193·1. J7

A SYNOPSIS OF THE JURASSIC ROCKS OFYORKSHIRE.

I. INTRODUCTION.

By VE RNON W ILS ON, PH.D., B.SC., D.LC., F.G.S.

OF the Yorkshireman it has been said he " ta kes all an'gives nowt " ; this mayor may not be true, but it aptly

applies to the Jurassic rocks of the county.Compared with other parts of the country Yorkshire certainly

t ook a maximum of sediments to fill its basin in Jurassic times.This great thickness of sediments is spread over the north-castsector of the county, and , for convenience, may be dividedinto four main t opographic units, with the plateau of theChalk Wolds in th e south-eas t const it uting a fifth unit .

T. In th e ext reme north, long rambling moorland tractsand hill ranges form th e Cleveland Hills and NorthYorkshire Moors.

2 . While the Cleveland area ma y be considered to formthe backbone of northeast Yorkshire, to the south ofit there occurs a magnificent line of dissected escarpments extending from the vicinity of Scarboroughwestward t o th e Vale of Mowbray ; these escarpments form the northern fringe of a wide belt ofmonotonously high ground, whose slope is graduallysouthward, known as the Tabular and HambletonHills areas. The continuity of the Tabular Hills, fromthe coast westward to Ryedale is broken at intervalsby a series of fine picturesque gorges which have beencarved out bv the consequent streams flowing southward from tlie Cleveland area. The Hambleton Hillsalso terminate, to the west, in a high escarpment,often dev eloped as cliffs over a IOO feet in height,overlooking the broad Vale of Mowbray.

3. To the south, the Tabular Hills pass down into th e broadflat alluvial plain formerly the site of th e PleistoceneLake Pickerin g. This stretch of low count ry is constricted to a narrow gap-the Coxwold-Gilling Gapin the west . The numerous streams flowing from thenorthern areas meander across this plain, and eventually, as the River Derwent, th e waters of this area

SYNOPSIS OF JURASSIC ROCKS ,OF YORKSHIRE. 249

find their way into the Vale of York and theHumber through the glacial gorge at Kirkham, southof Malton.

4. The Vale of Pickering is separated from the Vale ofYork, to the south-west, bv a series of low hills andridges intersected by numerous valleys, forming abroad spread of undulating country extending south,eastward to the Chalk Wolds plateau. This area isknown as the Howardian Hills and forms the southwestern flank of the Vale of Pickering.

The elongated Cleveland dome has an E.-\V. direction. Aswould be expected the lower Jurassic rocks form the core of thisstructure. Middle Jurassic rocks occur above the lower beds andhave low dips to the north and to the south of the dome. Onthe south side successively higher beds are encountered, andthe Tabular and Hambleton Hills consist entirely of UpperJurassic rocks which are eventually carried down below thealluvium of the Vale of Pickering. The northern and southernfringes of the Vale of Pickering are faulted, though the faultsare frequently obscured by the alluvium. The southern limitof the Tabular Hills is marked by a long E-W fault extendingfrom the coast to Helmsley in Ryedale; similarly a fault ofthe same magnitude, the Coxwold-Gilling Fault, forms thenorthern limit of the Howardian Hills. Between these faultsis buried an immense block of Jurassic sediments forming thefoundations of the Vale of Pickering.

In the west the Howardian Hills are separated from theHambleton Hills by the Coxwold-Gilling Gap, which owes itsorigin to the Coxwold-Gilling Fault and the Kilburn-AmpleforthFault and marks the southern limit of the Hambleton Hills.The joint effect of these faults has been to let down betweenthem a block of Jurassic sediments through a vertical distanceof about 600 feet, so that the Kimeridge Clay forms roundedhills in the Gap with escarpments of Lower Calcareous Griton the north and south sides (Plate 17). Tectonically theHowardian Hills constitute one of the most intricate areas inthe country; suffice it to say that the area is dominatedbv an elaborate network of E.S.E.-W.N.W. and N.E.-S.W.faults.

The general strike of these Hills is N.W.--S.E., and the rocksdip at low angles to the north-east, though both dip and strikeare much interfered with by the system of faulting.

No account of the deposits of the Yorkshire Jurassic basinwould be complete without mention being made of the roleplayed by the Market ,,,.eighton axis during their deposition. Thisaxis had a profound influence on the processes of sedimentationduring this period in the North of England. It has been fully

J. E. HEMINGWAY,

described by Prof. Kendall [24 and 25J* who has demonstratedthe abnormalities in the thicknesses of the Jurassic divisionsas the axis is approached from the north and south. Some ofthe divisions show petrological and palreontological differenceson both sides of the axis, which is considered to have been incontinuous movement, with brief intermissions throughout theperiod.

The Association has held three previous Field Meetings inNorth-East Yorkshire, in 1875, 1891 and 1906, and on each ofthese occasions the coastal geology was the primary object.Most of the classic sections of the Jurassic rocks in Yorkshireoccur on the north-east coast, and while full justice will be doneto them during the present meeting, considerable attention willalso be given to some of the excellent sections and other finefeatures to be found in the hinterland.

II. THE LIAS OF THE YORKSHIRE COAST.By J. E. HEMINGWAY, PH.D., B.Sc.

Cleveland has long been famous for the charm and beautyof its scenery. Its rolling moors, its sheltered valleys withtheir tiny villages, its coastline with its small fishing communities have been immortalized both by artists and writers.To the geologist the appeal lies principally, but by no meansentirely, in the coast line. From Blea Wyke Point northwardsto Redcar is an almost continuous exposure (30 miles in length)of the shales, sandstones and ironstones of the Lias. Thisclassic ground, the scene of the labours of Young and Bird,Sedgwick, Phillips, Tate and Blake, Fox-Strangways, Barrowand Buckman, is richly fossiliferous, and is the mecca of thosegeologists interested in the stratigraphy of the Lower Jurassicof Yorkshire, and the problems it presents.

The zonal classification adopted in this brief review of theLias of the Yorkshire Coast follows in the main that used bvDr. W. J. Arkell in his recent" Jurassic System in Great Britain."In this classification Arkell corrects many mis-statements madeby Buckman, and in so doing renders the Yorkshire sequencemore readily capable of correlation with the Lias of the remainderof Great Britain.

The Lower Lias.The Lower Lias occurs on the Yorkshire coast at only two

localities, Robin Hood's Bay and Redcar. At neither, however,is the lowest Hettangian exposed, and it is only at the inlandexposures that the pre-Planorbis beds may be seen. NearNorthallerton about 40 feet of paper shales are exposed yielding

• For list of References see page 289.

SYNOPSIS OF JURASSIC ROCKS OF YORKSHIRE. 251

Pteromya crowcombei throughout and abundant Ostrea liassicain the upper part.. The existence of the planorbis zone off thecoast can scarcely be doubted. Although it cannot be seenin situ, blocks containing this fossil are occasionally washed up

Stages. Zones. Subzones. Strata.

-------------------------------------Dumortieria moorei----------

Phlyseogrammoceras Blea Wykedispansum Beds

----------YEOVILIAN Lytoceras Pseudogrammoceras

[urensis struckmanni--------------------

Grammoceras Striatulumstriatulum Shales

------ --------------------Haugia variabilis Peak ShalesLillia lilli

----------------------------- (fJ

Peronoceras (lj

braunianum Alum Shale ;::l

Hildoceras ---------- Series ....Q)

bifrons and Peronoceras 0<0<

Dactytioceras ftbulatum t>commune ----------

FrechiellaWHITBIAN subcarinata

Harpoceras Harpoceras [alcifer Jet Rock[alcifer ---------- Series

Harpoceras exaratum--------

Dactylioceras Dactyliocerastenuicostatum tenuicostatum

---------- Grey ShalesT iltonoceras

acutum-----

Paltopleuroceras Part of the (fJ(lj

spinatum Ironstone Series ;::lDOMERIAN Q)

Amaltheus Sandy Series and ::amargaritatus part of Ironstone '"0

Series :@

at Robin Hood's Bay from submarine scars. The zone hasalso been recorded inland, in certain small sections and temporaryexposures.

The angulat1lm zone, the lowest part of the Lias exposed inthe coast, is seen only at Redcar, in a small upfold between thebucklandi beds. Here the upper 30 feet is exposed opposite

252 J. E. HEMINGWAY,

the town as a series of shales with occasional earthy limestonesand several shelly bands composed almost entirely of Gryphaaarcuata.

The lithological character of the angulatum and bucklandizone above is very similar. This latter zone is also only exposedon the shore at Redcar, where its whole thickness of some 160feet may be seen. Two beds of this series are particularlyinteresting; an 8-inch "Oyster Bed," extremely fossiliferous,containing most of the fossils found in the zone together withMontlivaltia hamei and M. guettardi. Two feet above this isthe" Cardinia band" a 3-inch mass made up largely of Cardinialisteri with occasional Unicardia and the ubiquitous Gryphaaarcuata.

The lowest zone found in the district which comes under theimmediate review of the excursion is that of Arnioceras semicostatum. At low spring tides the upper 36 feet of dark shaleswith thin shelly limestones may be seen midway between RobinHood's Bay village and Peak. The zone fossil and Arietitesturneri are fairly abundant, together with Gryphcea arcuata,Hippopodium ponderosum, Cardinia listeri, Nuculana and Dentalium,

The junction between the two succeeding zones, obtusum andoxynotum has not been defined. Together they comprise about70 feet of soft grey shales, with lines of nodules and hardercalcareous bands, of which the most conspicuous is the DoubleBand, two feet from the top. In the thin bed of shale above itseveral species of Oxynoticerates are recorded by Simpson [34J,indicating the oxynotum zone. The shales below yield Asteroceras obtusum at several horizons. Arkell therefore assumesthat most, if not all, of this 65 feet of shale belongs to the obiusumzone.

The raricosiatum zone, 105 feet thick, is similar lithologicallyto the beds of the zone below. It includes Buckman's' armatumzone' which he placed above his raricostatum zone, but whichwas found in Dorset below the raricostatum horizon. The bedsoccur in great arc-like scars on the north and south side ofRobin Hood's Bay.

The succeeding 102 feet is considered by Arkell [1J to represent the jamesoni and ibex zones. They are principally greyshales with a development of harder blue shale in the lower25 feet, and several dogger hands of siderite mudstone up to8 inches thick. In the upper 53 feet are found Paltopleurocerasaureum, P. rotundum, Polymorphites triuialis and other species,usually extremely fragile and preserved entirely in pyrites.These have been recorded below the horizon of Uptonia [amesoniin the jamesoni zone of Dorset. From this it has been concludedthat the zone of Tragophylloceras ibex and the upper [amesonizone are either missing or represented by unfossiliferous shales.


The zone fossil of the Prodactylioceras davoei zone is not foundin Yorkshire, but the occurrence of Oistoceras high in the series,together with Lytoceras is considered by Arkell [1J to be sufficientto include the succeeding 155 feet of shales in the dauoei zone.These shales become progressively more sandy higher in thesequence, so much so that the upper 30 feet was originallymapped with the Sandy Series of the Middle Lias. Twofeatures are outstanding. Near the top of the zone is a hardferruginous sandstone 4 feet 6 inches thick, which forms thefloor of Castle Chamber on North Cheek, Robin Hood's Bay.It contains layers of fossils, the capricorn ammonites beingprincipally species of Oistoceras. Dentalium giganteum is abundant in the upper part, Gryphrea cymbium is fairly common,and Proto cardia truncata is found occasionally. 23 feet belowthis is an IS-inch bed of thin sandy shales which passes intoa shell bed composed of Gryphrea cymbium and Oxyiomainreq·uivalvis, with some capricorn ammonites. This bed marksboth a lithological and stratigraphical change in the sequence,and was. originally taken as the base of the Sandy Series ofthe Middle Lias.

Mr. L. Bairstow, who has for some years been working onthe faunal succession of the Lower Lias of Robin Hood's Bay,informs' the writer he has established that the lithologicalsuccession of that portion of the Lower Lias which outcropson the shore in the southern part of the bay remains almostconstant; even in very considerable detail throughout the restof the outcrop northwards within the bay, although the distancebetween the ends of the outcrop ranges up to more than two milesfor some of these beds. The unexpected, highly detailedlithological correlation of these beds from place to place withinthe bay points to their deposition in extremely quiet conditionsof sedimentation, in waters of sufficient depth to be beyond theeffect of storm waters.

The Middle Lias.The Middle Lias is divided on lithological grounds into two

parts, the Sandy Series below and the Ironstone Series above.This, however, does not coincide with the palseontological subdivision. Buckman placed the upper limit of the margaritatuszone at the top of the Pecten Seam, leaving only about onequarter of the Ironstone Series in the spinaium zone above.It should be noted, however, that Buckman did the greaterpart of his work on the Middle Lias of Yorkshire near HawskerBottoms, where, because of the southerly thinning of the beds,only one of the four principal ironstones is recognised, and thatin avery attenuated form.

The Sandy Series is about 55 feet thick between Robin Hood'sBay and Hawsker Bottoms, but thickens to 70 feet near Staithes,


where it may be more easily examined. It is made up entirelyof sandstones and sandy shales, the former frequently welllaminated and occasionally ripple-marked and micaceous. Thesandstones are highly fossiliferous, with layers of Protocardiatruncata, Denialium giganteum, Avicula and Gryphcea.

The Ironstone Series is the most variable group of beds inthe Yorkshire Lias. In general the individual ironstone seamsthicken to the north-west, while the series as a whole thickensin the opposite direction. As a result of the thickening of theironstones with the concomitant thinning and pinching out ofthe intervening shales, the upper 28 fect of the Ironstone Seriescontains, in the Eston district, 20 feet 6 inches of ironstone.In the Eston Hills, off the northern edge of the Cleveland block,the Main Seam attains a thickness of II feet and immediatelyoverlies the Pecten Seam. In common with the other seams,it improves in quality with the thickening and to-day yieldsthe whole of the local ore used in the Cleveland iron industry.Although in the past this industry drew its ironstone from allthe seams and from localities all over Cleveland north of theEsk, the realisation of the thickening and improvement of theseams to the north-west resulted in a concentration of themining in northern Cleveland, with the closing down of thesouthern workings.

The thinning of the seams and the development of the shalesbetween them may be traced south-eastwards down the coast,until at Hawsker" Bottoms only a much attenuated PectenSeam is found, with manv thin seams and rows of ironstonedoggers. Here the Ironst~ne Series is 100 feet thick in comparison with a probable 60 or 70 feet in the Eston Hills.

The Staithes section (below), situated roughly midwaybetween Eston and Hawsker Bottoms, is fairly typical of tileMiddle Lias ironstones intermediate in development between thetwo extreme cases mentioned above.

Grey shales with rows of earthy ironstone nodules andshalv ironstones

Main Seam: ironstone with 14 inch shale parting ..Ferruginous shale ..Pecten Seam: 5 thin ironstones with maximum individual

thickness of 7 inches; with intervening shalesShaleTwo Foot SeamShales with thin ironstones and bands of ironstone

nodulesAvicula SeamShales with thin ironstones an bands of ironstone nodules

ft. ins.

8 66 2

3 6

4 52 7I 9

25 10

2 0

36 0

90 9


Here all the four seams are capable of identification, althoughthinner than at Eston. In the intervening shales are occasionalthin ironstones, representatives of thicker unnamed seams tothe north.

Typical Cleveland ironstone is an earthy grey rock weatheringto a rich brown or red. It is sometimes densely oolitic, the palegreen ooliths being irregularly distributed throughout the rock.They are embedded in a groundmass of mudstone, calcite cementbeing almost entirely absent. The ironstone is frequentlyriddled with worm tracks, which weather into high relief on thescars, taking on a rope-like, fucoidal form.

The Cleveland oolitic ironstones were originally consideredto have been oolitic limestones, the calcium carbonate havingbeen replaced by iron-bearing solutions. This theory of metasomatic replacement was finally disproved by Dr. A. F. Hallimond [16] who showed that the bedded ironstones were essentiallyaqueous chemical precipitates. Many of the Cleveland oolithsare composed of chamosite, and in no case was a residue foundwhich might indicate that originally they could have beencomposed of calcite. In addition, the calcite shells occurringwith the ooliths usually show no trace of alteration. Theoccurrence of siderite ooliths in the ironstone is considered byHallimond to be due to replacement of chamosite ooliths,which has taken place during agitation and possibly transportafter its formation.

The Upper Lias.Only in one locality, from Blea Wyke Point to Peak (Ravens

car) is the Upper Lias of Yorkshire fully developed. Elsewhere,to the north and west of the Peak Fault, the Dogger and in somecases beds of the Estuarine Series rest non-sequentially onshales of Whitbian age. All the zones and subzones of the Whitbian to the top of the bijrons zone are found in the 220 feet ofshales which comprise the type section of these beds at Whitby.

In the past the Upper Lias shales were of considerableeconomic importance. They yielded the raw materialr for thealum and jet industries, and although the great excavationsmade in the Alum Shales and the Jet Rock are now largelyovergrown or collapsed, they are at least some indication of thepast magnitude of these two industries, one now dead, the otherdecadent.

The lowest zone of the Whitbian, that of Dactyliocerastenuicostatum, is commonly known as the Grey Shales. This30 foot series of soft sandy shales is rarely exposed save on "thecoast, where again it is frequently covered by debris from thedeserted jet-workings above. It is characterised by the occurrence of several rows of tough, earthy, calcareous nodules aboutthe middle of the series which frequently contain the zone

]. E. HEMINGWAY,

fossil. Belemnites are common, particularly the large cylindricus,its phragmacone being often enclosed in a small nodule.

These shales pass upward without any well-defined lithologicalbreak into the Jet Rock Series. This includes the Jet Rockproper and the Bituminous Shales of the Geological Survey,totalling in all some 95 feet. The Jet Rock at the base, about25 feet thick, is a series of dense, black shales, well laminatedand smelling strongly of mineral oil when freshly broken.It does, indeed, yield 10 gallons of oil to the ton of shale,though an amount insufficient for its exploitation. The upperbed of the Jet Rock is a strong, well-bedded, argillaceous limestone from 4 to 6 inches thick, known as the Top Jet Dogger,in the upper surface of which are developed large, discoidalconcretions up to IS feet in diameter. The shales of the JetRock are characterised by many rows of pyritous nodules, someof which are fossiliferous. The gas chambers of ammonitesfound in these concretions are frequently filled with liquidbitumen. From 4 to 7 feet below the Top Jet Dogger is aremarkably constant bed of extremely large calcareous concretions, some measuring 4 by 3 by z feet. These are occasionallyfound broken in the cliff face, when the laminations of theshale may be seen to swing upward or downward near the nodule,and finally pass into it, where the laminse are seen etched out bysea erosion. Such sections afford striking proof of the penecontemporaneous origin of these concretions.

The best "hard" jet occurs only in the Jet Rock, and ismost abundant in the upper 10 feet. It occurs in elortgatedlenticular masses of all sizes distributed sporadically throughthe shale. In cross section these masses invariably show aflat lower surface, the upper surface being concave upwards.The writer has shown, in yet unpublished work, that jet isundoubtedly wood that has undergone a unique decomposition.Thin sections and etched surfaces show abundant evidence ofvegetable structure; indeed no part of any field examinedmicroscopically was found to be structureless. Annual rings,medullary rays, tracheids, bark and stem bases have beenrecognised, now crushed and contorted; but nevertheless ampleevidence is given that jet is formed from logs and sometimesfrom rafts ot wood. Some specimens of jet are silicified alonga central core, and here the wood is preserved in an uncrushedstate. From such areas wood-structures, in particular themedullary rays, may be traced into the skin of hard jet, wherethey are compressed and crumpled. Within the jet are frequentrows of included mineral grains, usually of microscopic size,though some are about a quarter of an inch in length. Theseare usually quartz, with occasional microscopic zircons, whichwere wedged into cracks in the original wood before sedimentation.


The upper 70 feet of the Jet Rock Series is characterisedby ammonites of the H arpoceras mulgravium type. These shalesare divided into four individual beds by two rows of pyritousnodules and a thin bed of siderite mudstone. The lowest ofthe shales is very similar microscopically to those of the JetRock, and is characterised by the presence of abundantcompressed Inoceramus dubius. Higher up in the series theindividual shales of the Jet Rock Series are progressively lessbituminous, although still dense, well laminated and dark incolour.

The Alum Shale Series derives its name from an upper bedof the division which was in the past extensively quarried foralum making. The basal bed of the series is a double band ofpyritous nodules, with occasional masses of siderite mudstonewith cone-in-cone structure, and masses of belemnites forminglimestones up to 3 inches thick and of several square yardsareal extent. The nodules contain the ammonite Pseudolioceraspseudovatum, peculiar to this hand, "not known in the southwest or Midlands of England, although something like it is foundin the north-west of Germany" [12]., This band is succeeded by a zo-foot bed of shale, the HardShales of the Geological Survey, which are less dense than thosebelow and almost non-bituminous. The uppermost bed of theHard Shales is as-inch .siderite mudstone referred to by FoxStra,ngways as " an indurated sandy band, becoming a distinctline of ironstone towards Whitby" [12J. There is no evidence,either field or microscopic, of this rock being arenaceous incharacter. Like the other hard bands of the Upper Lias,which weather to a dark red, it is a siderite mudstone.

The succeeding 70 feet of shales are characterised byammonites of the bifrons zone; Hildoceras bifrons, Dactyliocerascommune and abundant Nuculana ouum, both crushed anduncrushed. The upper 20 feet are known as the Cement Shales,since in them occur rows of nodules which up to two years agowere burnt to a fine hydraulic cement. The beds of the AlumShale Series are soft, grey and micaceous, weathering intocrisp fragments strikingly different from the papery weatheredshales of the Jet Rock Series. From these shales many largesaurians were obtained, including five species of Ichihyosauru«and three species of Plesiosaurus, as well as other genera.

Several points of interest have resulted from a microscopicalinvestigation of the shales of the Upper Lias. Spore cases werefound to occur in all beds of the Alum Shale and Jet Rock Series.A few microspores as well as several macrospores occur in theJet Rock and in the shale immediately above. The formerdecrease upwards through the sequence, but the latter showa marked increase midway up the Jet Rock Series. From

J. E. HEMINGWAY,

here they decrease progressively upwards until in the Cemen tShales only a very occasional spore case is met with.

Organic matter also varies considerably, being most abundantin the Jet Rock and, as would be expected, decreasing inabundance throughout the higher beds.

The occurrence of pyrites shows a definite variation. Inthe jet Rock it is found in small rounded spheres; in aggregatesof these spheres in the higher beds of the jet Rock Series; andin larger irregular masses with the smaller spheres in the AlumShale Series. The percentage of pyrites appears to increasefrom the jet Rock to the Alum Shale, but, without chemicalanalysis, it is impossible to state this with accuracy.

The most interesting variant of the Whitbian is the grainsize of the quartz contained in these sediments. In generalthe coarseness of the shales decreases from the base of thesuccession upwards. Microscopic quartz grains distributedalong the bedding planes are abundant in the jet Rock, andare most common and of largest size in the upper part of thebed. Above the jet Rock the distribution of quartz decreasesprogressively from bed to bed, both in quantity and grain-size,the Cement Shales being the finest of all the divisions. Thisis not in keeping with the conception usually held that blackshales were formed in deeper water, farther from land than weregrey shales. The black shales of the Jet Rock Series werelaid down under conditions similar to those of the Black Seato-day, except in depth. The anomaly that those sedimentslaid down in the quietest, and presumably the deepest, watersare coarsest in grain can only be explained by their sedimentation being accompanied by slight orogenic activity of thesurrounding landmasses. The carrying powers of the riversflowing into the basin would be increased to a small butmarked degree, with the result that slightly coarser materialwould be carried into the basin. This is not opposed to theopinion that black shales represent sedimentation understagnant conditions. While the slight rejuvenation of therivers may have to a small extent increased the depthof the upper aerated waters of the basin, the deeper waterswould not be affected except that minerals of coarser grain wouldbe contributed to their sediments.

From jet Rock times onwards to the end of the Whitbian,the basin is pictured as a sea being gradually filled up bysediments of rivers which were progressively decreasing in theircarrying power. Subsidence of the floor of the basin wasprobably taking place, but at a slower rate than deposition.As a result the sea floor was built up until at the end of theWhitbian the whole of the Yorkshire basin was an area of

SYNOPSI S OF JURASSIC RO CKS OF YORKSHIRE. 259

comparat ively sha llow, aerated water, fed by rivers of extremesluggishness.

The Upper Lias to the East of the Peak Fault.Only on the downthrow side of the Peak Fault are the

Whitbian and the Yeovili an fully developed. Here, above theAlum Shale Series is about 60 feet of dark shales largely hiddenby scree and boulders of the sho re . They have yielded speciesof H augia and were named by Buckman the Peak Shales.

They are succeeded by a 60-foot series of micaceous shaleswith occasional bands of impure ironstone, the lowest bed ofthe Yeovilian. These are the St riatulum Shales from whichhave been obtained Grammoceras striatulum, G. toarcense andother species. The S triatulum Shales are only poorly exposedand their junction with the Blea Wyke Beds above is hidden.

The Blea Wyke Beds, ab out 100 feet in thickness, are dividedinto the Grey Beds below and the Yellow Beds above. TheGrey Beds, 38 feet in thickness, are principally fine grained,false-bedded sandstones, overlyin g 7 feet of soft grey, sandyshales. Lingula beani is found throughout the whole of theseries, but is particularly abundant in a bed of nodules at thebase. The upper part of the sands to ne is characterised bythe presence of burr-like masses of Vermicu laria compressa andSerpula deplexa . The ammonites, of which Phly seogrammocerasdispansum, Hudlestonia affinis , and H . ieykensis have beenrecorded, indicate that the Grey Beds belong t o the dispansumsub-zone.

The Yellow Beds, 60 feet thick, are a series of soft micaceoussandstones, ferruginous and with occasional limey concretions.They are divided into three massive blocks by two softer bands,the up per of which is a sandstone with abundant , lar ge flak esof mica; 25 feet from the base is a thin bed full of T erebratulatril ineata, wit h occasional Trigonia ramsay i and Gresslyadonacifor mis .

It is succeeded upwards by a coarse green sandstone 26 feetthick which is entirely nnfossiliferous. This was form erlygrouped with the Inferior Oolite, but was considered as Liassicby Dr. Rastall , who has been followed by all later write rs. Itshould be pointed out, however, that the N erin aia Bed above ,which is usually t aken as the base of the Dogger , is a shell bedof only limited extent. Although admittedly marking a nonsequence at Blea Wyke Point , it thins out to the north and south .where it is impossible to distinguish between the sandstonesabove and below. there being no bre ak , beddin g plane orlithological dist inction .

According to Dr. Arkell, at least the lower 25 feet of theYellow Beds may be assigned to the Dumortieria sub-zone,


while a recent discovery in the collection of Dr. Rastall fromBlea Wyke indicates that the succeeding zone moorei is alsorepresented in the Yellow Beds.

The Blea Wyke Beds thin off considerably towards thePeak Fault, a mile north-west of Blea Wyke Point. Moreparticularly is this marked in the Yellow Beds, which near thefault are only 27 feet thick, while the GreJ Beds are only a fewfeet thinner than at Blea Wyke. Although the TerebratulaBed cannot be traced near the fault, the occasional pebble bedsin the Yellow Beds-never more than 3 inches thick at Blea\Vyke-are here found to be thicker and more numerous, onereaching 18 inches in thickness.

The Peak Fault.The Peak Fault, with a throw of 400 feet, hrings the Lower

Estuarine Series against the Sandy Series of the Middle Lias,and forms the western limit of the full development of theYeovilian. As has already been stated, to the north-west andwest the Dogger rests, except in a few limited localities, uponthe Cement Shales of the Whitbian, while on the downthrowside all the zones of the Whitbian and Yeovillian are found.

A possible explanation of this (a modification of that whichfinds general acceptance) is that in post-Whitbian times, possiblyafter the deposition of the Grey Beds of the Blea Wyke Series,the Cleveland block to the west was elevated by the line nowfollowed by the Peak Fault. This formed a broad monoclinalslope, eventually broken by further movement which wasresponsible for the initiation of the Peak Fault. Movementcontinued during the Yeovilian in a series of small throws,which carried lower and lower beds of the upthrow side into thezone of wave action, where they were 'eroded away, and in partincorporated in the Yellow Beds. Erosion kept pace withfaulting, with the result that at no time was there any greatfault scarp in existence. The Yellow Beds accumulated off theedge of the elevated block. Only deposition of material insuch a way is in keeping with the thickening of these bedsaway from the Peak Fault, a fact not previously recognised.Phosphatised fragments of nodules and striatulum ammoniteswere swept from the block down the slope, forming the pebblebeds which thin away from the fault. The green grit abovethe Yellow Beds represents the coarser sediment finally fillingthe depression east of the block. Later a depression both ofthe block and the area to the east resulted in the depositionof the Dogger over the whole of North Yorkshire. In postMiddle Oolite times the fault moved a further 200 feet, givinga maximum throw of 400 feet.

SYNOPSIS OF JURASSIC ROCKS OF YORKSHIRE. 26r

III. THE MIDDLE JURASSIC ROCKS.By MAURICE BLACK, Ph.D., M.A., F.G.S.

1. OUTCROP AND GENERAL SEQUENCE.The Middle Jurassic Rocks in Yorkshire consist principally

of deltaic deposits, interrupted at three levels by marine beds.In the coast-section they rise from the sea in Gristhorpe Bay,and there are thin representatives of all except the lowest bedsin the rocks between this bav and Red Cliff. Northwards' thebeds thicken, and the outcrop spreads inland over the low groundwest of Scarborough and Scalby; north-west of Cloughton theoutcrop widens again, and rocks of this age underlie the greaterpart of the North-East Yorkshire Moors.

In the western escarpment the Red Chalk rests directly uponthe Lower Lias near Market Weighton, and Middle Jurassic bedsdo not appear in the section to the north until Kirby Underdaleis reached. Through the Howardian Hills the deltaic bedscontinue to thicken, and the Middle Jurassic forms a broad butmuch faulted outcrop. Beds of this age are covered by theUpper Jurassic in the Hambleton Hills, and make a narrowoutcrop in the steep escarpment; north of this the deltaicbeds form the Cleveland Escarpment and the broad expanseof moorlands which spread eastwards to the coast.

The Market Weighton Axis appears to have formed a broad,unsubmerged E.-W. ridge during the deposition of the MiddleJurassic. The thinning of the various beds of this age againstthe axis appears to be a result partly of reduced sedimentationand partly of repeated erosion. It has recently been shownthat the principal upward movements, accompanied by erosion.took place at the end of each deltaic episode [3J.

The area to the north of this was steadily sinking with anaxis of maximum depression running approximately from thePeak to Burton Howe. In parts of the moorland area,this axis seems to have had some influence upon the depositionof the marine members, for the character of the sedimentsin several cases changes either at this line or at almostparallel lines lying a little to the south. These positions areindicated in Fig. 33 and Fig. 34. On the coast the MilleporeBed reaches the axis, but is unrecognizable further north. Onthe western escarpment the Eller Beck Bed (ferruginous facies)replaces the Hydraulic Limestone' (calcareous facies) near SuttonBank; the Whitwell Oolite (equivalent of the Millepore Bed)dies out near Kirby Knowle, about three miles north; and,finally, the calcareous development of the Grey LimestoneSeries gives way to a more gritty (northern) facies some five milesnorth again, between Over Silton and Osmotherley. These

262 :M. BLACK,

changes take place successively northwards in a st rip of countryeight miles wide, and lying just south of the crest of the ClevelandAnticline.

The sequence of Middle Jurassic beds on the coast is asfollows I :-

UPPERESTUARINESERIES

GREY LIMEST ONESERIES

MIDDLEESTUAR IN E SERIES

MILLE POREB ED

L OW E RESTUARI NES E RI E S

D OGGE R

(Cornbrash)

1Mudstones, shales and sands tones . dom in antly level bedde d . wi th a variable thick n ess of strongly current-bedded sa nds tonean d shales at t he base . . . . . .Moor Grit: curren t -bedded grit and quartzite

(Impure Iirseston e, sandstone and shale,l marine .. . . . . . , . . . .( Shales a nd sandstones, wi th occasionall coaly bed s

{Calcareous and ferruginous sa nds to nes, withnodular beds above ; marin e . . . .

IShale , and thick , current-bedded ferruginoussa ndst one (" Est uar ine " Bed s) . . . .Eller B eck Bed: thin flaggy ferrugino ussands tone , rest in g on shales and ironstones :

12::~:a~~ous s'ha les ~i'th thi~ coal 's~ams i~the upper part . la rge len ti cu lar masses ofcurren t- bed ded sandst one in t he lower(" E stuarine" Beds) .. . . . . . .

( Hard ferrugin ous sandstone with the N erincea1 B ed a t the base

(Uppe r Lias)

ft .

16 0

4°

72

110

15

160

II

II. CONDITIONS AT THE END OF LIAS TIMES.In most of the coast sections the highest Liassic beds were

removed befor e the deposition of the Dogger, but in severallocal iti es remn ants have been preserved . These show that incertain parts of Cleveland th e marine shales of the Lias passgradually upw ards into plant-bearing beds, and there is goodreason for supposing that these non-marine conditions starte dbefore the end of th e Lias.

. In many localities where th e Dogger is absent the highestammonites found below th e plant-bearing beds indica te horizonsin the middle or upper part of the Whit bian ; some twentyfeet of barren shales follow, with a gradual passage from typicalalum shale to a grey sandy shale, followed by carbonaceousor coaly beds .

The' Upper Lias and the Lower Estuarine Series proper areusually separate d by at least one well-marked surface of erosion.Often there is another erosion surface , slightly above the baseof the Lower Estuarine Series : th is cuts through th e lowest

I Modified from tb e section by Fox-Strangways and Barrow (14 . pp. 23-24) meas ured in tbedills above Blea w yk e, wber e tbese bed s a re best developed. The part above tbe Moor- Grit ,whicb is abse nt at th is localit y, has been add ed t o complete the sect ion.

L.oow£,'R

c.o~£,~ ES TU,,"'R.,rlt.

~ ~

u PP tR: l STUA 'QI t'i C S £Q.IE S

IIIIII/If~~IIIIII

E 5£'Q1E.5

""DDI. £, (..!J 'f \J ,Q.~ lf"<l~(4'..

.ltC('1iIl

''''

""' L.I..t= Dc~~ ~~

uJ a 5 w~&1 ~ 6 f- :s "g - ~ IX % )11 ~ > 8<~ d ~ g o( .; ~ ~ . j<tI "§ i 0 w ~ .~ 3 x :;: 'i N- LJ U oJ .J X <): .......

S ~ P: III U "' -c z

JI i> %w W ~~ ,; 7; ~ . ~ Z :J

~ 6 ~ "i!<t 0 ~~ Z .J I- -e ~ [II,. 0 " in 0:; Ct l:J~ ~ ~ > ffi r] ~ ~ No v f- "' :. 1Il _., ~~ 6 iil " 0 ou ;>l!. u ! "

UPPER ESruAR INE S ER I E SAEY IL IM~5TO"'C I sl'q;u! I I I n

MIDDLE

~ CS 1'"UI\'t./N f:. Se:~, E. S

~ .~_ . LO WE D , ••<~ . " .FI g. 33 .~••••••_... ~<...,<s.

' 00

, 0

' 00

1000 F t [ T

w"

. ~ ~w.. 0

... S z

~:t ~::>.~ ~ <:" ~

,.tii .

L '00 .. ~,(I "ij !l u s a

5::<: 3 " <: it

~r-<<;.0:0>-l

<.H

-<or

"di<lo!"'CIi'lor>cr,(/)

on

o "5 10 ':7 2 0 MII. e 6

~ I . ! ! , I! ,. I , ! ! ! I • • • 1 ,

Fros, 33 AND 34.-DrAGRA MMATIC SECTIO NS TO SHOW THE V ARI ATIONS IN THICKNE SS OF THE M ID DL E JURASSI C BEDS ACROSSTHE C LEVE LAND ARE A. F ig. 33. T h e W e s t e rn Escar p ment; Fig. 3 4 . The Coast Section .

H-o"'"""

M. BLACK,

estuarine beds into the Dogger, and sometimes into the AlumShale below. The marine beds which are found between thesetwo erosion surfaces show a very wide range in lithology, butfor convenience are grouped together under the name Dogger.

In the following account the marine beds, which act asdatum-levels, will be dealt with first, and the sediments ofdeltaic origin will be described separately.

III. THE MARINE BEDS.1. The Dogger.

Although the Dogger rarely contains ammonites, and thecontemporaneity of the various developments is in doubt, thisbed provides a useful and easily mapped base for the MiddleJurassic in Yorkshire. In the area near the coast the Doggershows several distinctly different developments, and these arebest treated separately.

The Whitby District.Here the surface on which the Dogger rests is smooth over

large areas, and consists of eroded Alum Shale. There is nosign of river erosion, and, the surface was probably planed offby the sea. The Dogger is represented by a ferruginous sandstone, with conspicuous white specks, giving it a highly characteristic appearance. The white mineral appears to be relatedto kaolin, and is doubtless derived from weathered detritalfelspars.

In this area the Dogger contains few fossils. Its appearancevaries a little according to the distribution of ironstone concretions and the state of weathering, but the total thicknessdeparts little from about five feet. The following section,measured in the Peak Alum Quarries, is representative :-

ft. ins.(Estuarine Sandstone)Ferruginous parting .,Brown ferruginous rock, compact and sideritic above.

arenaceous below. One foot from the base is a teninch band full of cementstone pebbles, with derivedLias fossils ..

Shale with cementstone pebblesCompact dark brown mudstone(Alum Shale)

2

3 10

58

5

Blea Wyke Point.On the south-eastern side of the Peak Fault the character of

this formation is distinctly altered; the Dogger here consistsof ferruginous sandstones, with the highly fossiliferous N erinceabed ten feet from the top. Nearly all the species recordedfrom the Dogger have been collected from the Nerincea Bed,which is only about nine inches in thickness. The fossils


include Nerinaia cingenda Phil., Astarte elegans Sow., Chemnitzialineaia Sow., Cucullaa cancellata Phil., Gresslya abducta Phil.,Pteroperna striata Bean MS., Trigonia v-costata Lyc., and anumber of corals of the genera Montlivaltia and Thecosmilia.This bed originally must have been a shelly limestone, evenmore fossiliferous than the similar limestones in the hills westof Bilsdale. It is completely unlike any other development ofthe Dogger in this part of Yorkshire.

The Howardian Hills.In this area the Dogger has an extremely irregular dis

tribution. Where it is present it is represented by ferruginouslimestone or sandstone, frequently enclosing cementstonepebbles.

2. The Eller Beck Bed and Hydraulic Limestone.The Eller Beck Bed is found some 100-150 feet above the

Dogger, and where the Millepore Bed is absent, it provides auseful plane of reference in dealing with the non-marine beds.Lithologically it consists of ironstones, ferruginous sandstonesand shales, with marine fossils, which are almost all lamellibranchs.

In the coast section the Eller Beck Bed is not seen south ofIron Scar, between Cloughton and Hayburn Wyke. In thewestern escarpment it can be traced southwards to the neighbourhood of Sutton Bank, where the ferruginous facies is replaced by a calcareous one. From this point southwards intothe Howardian Hills this marine band is known as the HydraulicLimestone.

In the Howardian Hills this bed is not as a rule well exposed,but it contains a distinctive band of fine-textured, grey argillaceous limestone, which serves to mark the outcrop. This rockis hard and breaks with a conchoidal fracture, so that the fewfossils which it contains are not easy to extract.

Although the Eller Beck Bed is frequently crowded withfossils, specific identification is often difficult. Characteristicforms are Astarte minima Phil., Pleuromya, Gervillia and severalspecies of Pholadomya.

3. MiIlepore Bed and Whitwell Oolite.On the coast, the Millepore Bed consists of calcareous sand

stone containing an abundance of crinoid ossicles and fragmentsof the Bryozoan Entaiophora straminea (Phil.). Northwards,it becomes less calcareous and more ferruginous and arenaceous,until it finally passes into unfossiliferous sandstone and becomesunrecognisable.

In the Howardian Hills, this marine band is represented bya strong white oolitic limestone, the Whitwell Oolite. In this

266 M. B'LACK,

area, the same Bryozoan, Entalophora straminea (Phil.) , is present,but not common, and the rest of the fauna is curiously differentfrom that of the Millepore Bed on the coast, especially in theabsence of gasteropods, and the greater variety of echinoidsand brachiopods.

4. The Grey Limestone Series.This series rises from the sea in Gristhorpe Bay, and is seen

in the cliff at Yons Nab, where it is about seven feet thick.The next satisfactory exposure is at White Nab, where it isconsiderably thicker, and includes several very hard ironstoneand limestone bands, on the surface of which Gervillia scarburgensis Paris may often be seen in great abundance. Otherfossils common at this locality are Pseudomonotis lycetti RoIlier(the Pteria braamburiensis of the Survey Memoirs), Trigoniasignata Lye., Ostrea fiabelloides Lam., and several species ofBelemnites.

North of Scarborough, these beds reappear at HundalePoint, near Cloughton, where they are excellently exposed, andhighly fossiliferous', Fox-Strangways suggested a broadgrouping of the beds here into three lithological divisions:A lower division containing impure limestone bands, withabundant Gervillia, a middle division of sandy marls, grits andcalcareous sandstones, with crinoid ossicles in large numbers,and an upper division, principally shaley, with a great numberof fossils, including abundant belemnites and a few ammonites.

At Blea Wyke, the section is considerably thicker, largelyowing to the presence of flaggy sandstones with Pleuromya,which appear both at the top and bottom of the section. Thehigher sandstone can be traced for a considerable distanceinland, where it is characterized by the presence of a smallspecies of Gryphcea.

In the Howardian Hills, the Grev Limestone Series is aboutforty feet thick, consisting of brown, porous grits, overlyinghard, siliceous, flaggy limestone. The usual fossils are quiteplentiful here, and include Pseudomonotis lycetti, Gervilliascarburgensis, Ostrea flabelloides, Perna rugosa, Myacitessecuriformis, and Trigonia signata.

5. Correlation of the Marine Bands.In dating the various beds of the Middle Jurassic in York

shire, reliance has to be placed principally upon the ammonitesfound in the marine bands. Unfortunately, these are not atall common, and only serve to give rather wide limits to thepossible ages of the intervening strata.

The Dogger, on detailed investigation, proves to include beds

I A detailed section at this locality is given in Foz-Strangways and Barrow, [14], p, 38.


of various ages from the striatulum to the mllrchisonce zone.Mr. W. E. F. Macmillan [28J has collected an extremely interestingseries of ammonites from beds usually classed with thisformation. These show that much of the ferruginous shalewhich has generally been regarded as representing the Doggerin the moorland dales, is really of Yeovilian age. Beds ofAalenian age are present at a few localities, such as Glaisdaleand Trucky Rock Hole, west of Whitby, where ammonitesindicating the opalinum zone are found.

At other localities, such as Loftus and the hills west ofBilsdale, the Dogger is of later date and yields species characteristic of the murchisonaJ zone. This still leaves the comparatively unfossiliferous Dogger of the coast and the shelly N erinceaBed of Blea Wyke Point undated. Some finely ribbed Dumortierie, collected by Dr. Rastall from the upper part of theYellow Sands, have been examined by Dr. Spath, who assignsthem to the moorei hemera. Thus it may well be that partof the overlying greenish yellow sandstone and the N erinaaBed above are of Middle Jurassic age, and may be retainedin the Dogger in the usually accepted sense.

The Eller Beck Bed and the Hydraulic Limestone have upto the present yielded no fossils by which their exact horizoncan be fixed.

The Whitwell Oolite and Millepore Bed also contain butfew species which can be relied upon for purposes of dating thebeds. A spinose rhynchonellid, Acanthothyris crossi (Walker),found in the Lincolnshire Limestone and in the Buckmani Gritof the Cotswolds (discites zone), appears to be present in theWhitwell Oolite, which may thus be of discites date [32].

The Grey Limestone Series has yielded a number ofammonites, which give an indication of the general age of thebeds as a whole [8 and 9] ; unfortunately, Buckman's determinations were made from museum specimens, and it is notknown from which beds within the Grey Limestone Series theywere collected. The best interpretation seems to suggest theblagdeni zone, but it is possible that others are represented.

Above the Grey Limestone Series, no marine horizons areknown in the Middle Jurassic, and the upper limit of theEstuarine Series is fixed by the Cornbrash, which in this areaappears to belong entirely to the macrocephalus zone (Callovian).

IV. THE DELTAIC BEDS.The term "Estuarine Series" is misleading when applied

to the Middle Jurassic of Yorkshire, since the facies here ischaracteristically deltaic, and the beds are strikingly similarto the Coal Measures.

As in the Coal Measures, the bulk of the material in theEstuarine Series was deposited as delta topset beds, and, with

268 M. BLACK,

the exception of the Moor Grit, there is little that could beregarded as foreset beds. Deposition seems to have taken placein extensive, shallow pools or fresh-water lagoons on the deltasurface, but occasional desiccation-cracked layers show thatsubaerial conditions existed from time to time.

Cutting through the parallel-bedded sediments formed inthis manner, are the filled-in courses of distributary streams whichcrossed the delta surface. In the coast-section, these streams,channels or " washouts" appear most abundantly in the lowerpart of the Lower Estuarine Series, and near the middle of theUpper Estuarine Series, but they are also to be found at otherlevels.

The fauna of the Estuarine Series is scanty. Fresh-waterlamellibranchs are found at certain places. The earliest occurrence is. that of Unio kendalli Jackson in the Lower EstuarineSeries at Saltwick, In the Upper Estuarine Series, Uniodistortus Bean and Unio hamatus Brown are found in greatnumbers near Scarborough, and at Gristhorpe and Burniston.Other molluscs are not known in the Estuarine Series. Insectremains have been collected from the drifted plant beds ofScalby \Vyke; they are principally wings of Orthoptera, andwing-cases of Coleoptera.

Fossil reptilian footprints have been found at severallocalities. They were first recorded from the Lower EstuarineSeries at Saltwick by Mr. H. Brodrick [7J in fallen blocks, andthe bed from which these were derived was subsequentlyidentified by Prof. Kendall. Footprints in the Upper EstuarineSeries were first recorded by Mr. J. A. Hargreaves [17J inBurniston Wyke. Similar prints have recently been foundat Bloody Beck, in the Fylingdales Moor, and at Loskey Beck,in Spaunton Moor, north of Kirby Moorside, but no traces ofbones have been found at any of these localities.

Autochthonous plant-beds and coal seams, resting upona seat-earth full of ramifying roots, are of frequent occurrencein the Estuarine Series, and several ecologically distinct typescan be recognized. The simplest, and most frequently occurringplant community is a pure growth of Equisetites; the plantsseem to have grown in water, often several feet in depth, fortheir upright stems are frequently found to be embedded infinely laminated sediment. In other examples, the stems arerecumbent, and separated by thin films of grey shale, or arepressed together without sediment to form a thin coal seam.Plant-beds of this kind are found throughout the EstuarineSeries, and good examples may be seen in the lower part of theStaintondale Cliffs.

A slightly more advanced stage in colonization is found inother plant-beds, which begin in a similar way, but contain inthe higher parts abundant remains of one or more species of

SYNOPSIS OF JURASSIC ROCKS OF YORKSHIRE. 26)

ferns. The usual species found associated with, or replacingEquisetites in this way are Coniopteris hymenophylloides (Brongn.),C. arguta (L. and H.) and Cladophlebis denticulata (Brongn.).

Plant colonization of the delta flats thus usually startedwith Equisetites (either E. beani (Bunb.), or E. columnaris(Brongn.), followed by some species of fern, and it is only rarelythat a more varied vegetation occurs spread over the delta. Attwo or three levels in the Middle and Lower series, however, bedsof a similar type are found, but with an extremely rich and variedflora. It is from these deposits at Gristhorpe, Cloughton,and Hayburn Wyke that most of the finest specimens of plantsfrom the Estuarine Series have been collected.

In addition to the autochthonous plant-beds, there are alsodrifted plant remains in some parts of the Estuarine Series.These are particularly important in the Upper Series, wherethe flora has been worked out from drifted material, in theabsence of prolific autochthonous beds. The larger fronds areusually found in the sediments filling distributary channels,and the smaller leaves and fronds in laminated sediments,apparently deposited in shallow lakes on the delta surface.

Stratigraphically, it is convenient to recognize three plant-bearing series :

3. Upper Estuarine Series2. Middle Estuarine Series.1. Lower Estuarine Series (below the Eller Beck Bed).

1. The Lower Estuarine Series.The earliest plant-beds in some areas follow the Liassic shales

without any marked discordance, but elsewhere they are underlain by the Dogger. Wherever these beds occur they are themselves strongly eroded and channelled, so that comparativelysmall relics are preserved beneath the Lower Estuarine Series.The best known of these are the Thinnfeldia Leaf-bed at RoseberyTopping [38 and 4OJ, and the thin plant-bed in the Loftus andBoulby Alum Quarries.

The floras are somewhat varied, and appear to be controlledby local conditions; but where they give any indication of theirage, they suggest relationship with Lower rather than withMiddle Jurassic floras. The plants at Loftus are found in a bedof coaly shale, and include a Pagiophyllum which is either theLiassic P. peregrinum (L. and H.), or a variety of this species.The Leaf-bed at Roseberry Topping contains layers ofThinnfeldia leaves almost to the exclusion of detrital sediment.Associated plants are Zamites gigas L. and H., Anomozamitesnilssoni (Phil.) , Ctenis falcata L. and H., and Ctenozamitesleckenbyi (Leek. ex Bean MS.). Further details may be foundin Dr. Thomas's accounts of this plant-bed, quoted above.

_ _ _ _ _ - ~_ ":":=.=--=----=-------=-----=-~-_ _=__=__o."=.:::: 14--- - . -13

12

il.§~~;·j5~:~;:i~~~~~:.~_~::::=.:.~::~.~~_~.~~~.:·~~~~~~:~.:.:.~32

SCAl.tb'rcer

o

'0

.030

..Q...Qa..&iiiIIiiL-P~-AQ......J:;;:P....Q.5)e.....,.<Pp~~o0 ~ C) OClOO C::::::> c>~~~~'"'(5"'C5""'e5"""O'o Q§D

FIG. 35.-SECTION AT LOFTUS ALUM QUARRIES, showing the position of the Pre-Channel Plant Bed.

140

50

q. Shales.r3. Sandstone with vertical root-like

markings.12. Grey Shales.II. Current-bedded sandstone filling

channels in the underlying beds;this passes laterally into a thinbed of sandstone.

10. Dark, carbonaceous shale.9. Yellow-weathering sandstone.

8. Grey shale with fossil plants:Pagiophyllum peregrinum (L.and H.) and Coniopteris hymenopltylloides (Brongn),

7. Dark coaly bed.6. Nodular, sideritic shale: some of

the ironstone nodules fossiliferous.

5. Ironstone nodules with ammonitesof murchisonae age, and pinnulesof Laccopteris,

4. Pebble layer; chiefly cementstonefragments, but some probablyphosphatic.

3. Dark, reddish-brown mudstone.2. Shale, sandy towards the top.I. Alum shale with cementstone

nodules containing Whitbianammonites (bifrons and communis).


The plant-bed at Loftus overlies shales containing ammonitesof the murchisonce zone (see Fig. 35), whereas the ThinnfeldiaBed of Roseberry rests directly on the Alum Shale.

The abundance of Pagiophyllym. peregrinum at one locality,and of Thinnfeldia rhomboidalis at the other, emphasizes theLiassic affinities of the flora.

In the Whitby area, the Dogger is followed by shales andsandstones of the Lower Estuarine Series with no appearanceof unconformity at the contact. Some distance up in theEstuarine Series, however, there is a level at which powerfulchannel erosion has taken place. The effects of this erosionhave been described by many authors [2, 13, 18, 30, 43], forit is one of the most conspicuous features of the lowestestuarine beds in this area. The channels cut into the alreadydeposited basal beds of the Estuarine Series, and in manyexamples they have removed the Dogger, and cut into theAlum Shale below. \Vhere this has happened, the lower partof the channel-filling contains a conglomerate of ironstone andcementstone nodules, washed out of the Dogger and the Lias:the rest of the eroded hollow is usually filled with stronglycurrent-bedded sandstone, often in thick massive wedges.Phenomena of this kind are frequent in the coast section, andmay be seen in the Peak Alum Quarries, at the LighthouseS.E. of Saltwick _Bay, on the shore just east of Whitby, andin the Boulby and Loftus Alum Quarries.

A similar channelling, but on a greater scale, is found atthe same horizon in the western escarpment of the ClevelandHills. In some localities here there are plant-beds only ashort distance above the erosion surfaces, and it is interestingto notice that the floras still retain Liassic relationships [38].Examples of deep erosion of the Lias, cutting down into theJet Rock, have been described in this area by Dr. Rastall [30],whose account of the Dogger also includes an excellent descriptionof the erosion phenomena which later affected these beds.

The streams which eroded most of the channels higher upin the Estuarine Series were probably powerful distributaries,which meandered across the delta, and carried the sedimentlater to be deposited at the advancing delta-front. On accountof the great depth to which the earlier channels have beeneroded, however, it seems likely that they were preceded byactual uplift, and that they were not merely the normalincidents in delta growth which the channels of the UpperEstuarine Series appear to have been.

Plant-beds accompanying, or closely following this earlyperiod of channel erosion, are well seen at several places in theCleveland Escarpment. At Hasty Bank, near Ingleby Greenhow,for example, Thinnfeldia is still quite abundant, and the othercommon forms are Equisetites beani (Bunb.), Sagenopteris .

272 M. BlACK,

Phillipsi (Brongn.) var. major Seward, Ptilophyllum pecten (Phil.),Anomozamites, and T amioptcris,

This assemblage is similar to the larger flora described byDr. Hamshaw Thomas [38] from the upper plant-bed at Roseberry Topping, where rocks containing this flora rest uponthe eroded surface of the Thinnfeldia Leaf-bed. In reviewingthe significance of this flora, Dr. Thomas points out that severalof the dominant species, such as Iv[arattiopsis anglica Thomasancl Thinnfeldia rhomboidalis Ett., are distinctly Liassic incharacter. A similar flora is found near the base of the LowerEstuarine Series at Marske Quarries, north of Guisborough[27 and 39].

Near Whitby, plant-beds of this age have yielded aninteresting series of Bennettitalean inflorescences; nearly all thespecies are distinct from the inflorescences found in the MiddleEstuarine Series. Accompanying these are Bennettitaleanfronds, such as Zamites gigas L. and H., Ptilophyllum pecten(Phil.), and Otozamites parallelus Phil., and there are also afew species of Ferns.

Farther south, at Hayburn Wyke, the flora consists largelyof Ferns, such as Coniopteris hymenophylloides (Brongn.), C.quinqeloba (Phil.) , Dictyophyllum rugosum L. and H., andMatonidium goepperti (Ett.) , together with Bennettitales suchas Otozamites obtusus (L. and H.) and Zamites gigas L. and H.

2. The Middle Estuarine Series.South of the Cleveland axis, this series is separated from the

Lower Estuarine Series by the Millepore Bed. In the coastsection, the bedding is much more regular than that of the otherestuarine beds, and contemporaneous erosion phenomena, suchas distributary channels, are almost entirely absent.

This series contains the plant-beds of Gristhorpe andCloughton, which have added so much to our knowledge of theMiddle Jurassic flora. The work of Dr. Hamshaw Thomashas shown that the fossils contained in these beds are fragmentsof plants which grew almost on the exact spot where the fossilsare now found. For this reason, although the flora is an extremelyrich one, remains of individual species have an extraordinarilylocal distribution; they may dominate the flora at one place,but be entirely absent a few yards away. This is entirelydifferent from the distribution of fossils in the drifted plantbeds of the Upper Estuarine Series, in which one beddingplane may be strewn with the remains of a few species more orless evenly over a considerable area.

The flora consists principally of Bennettitales, Ginkgoales,Conifers, and Ferns, together with a few other Pteridophytes.Perhaps the most interesting members of this flora are theCaytoniales, which were first discovered by Dr. Hamshaw Thomas

SYNOPSIS OF ]l'RASSIC ROCKS OF YORKSHIRE. 273

at Gristhorpe, and have since been found at widely separatedlocalities in Europe and Greenland. The Yorkshire species,Caytonia sewardi Thomas and Gristhorpia nathorsti Thomas,are the earliest known plants bearing closed or angiospermousfruits in Great Britain, and they show distinct evidence of aPteridosperm ancestry [41J. This suggestion has recentlyreceived confirmation in the discovery of a Mesozoic (probablyMiddle Triassic) Pteridosperm flora, with both male and femaleinflorescences strikingly similar in some respects to those ofthe Caytoniales [42].

3. The Upper Estuarine Series.Where it is well developed, the Upper Estuarine Series is

divisible into two main parts:" Level-Bedded {DOminantly level-bedded shales, joint-clays, and

Series fine-grained sandstones.1. Current- r (b) Strongly current-bedded sandstones and shales.

Bedded Series \ (a) Moor Grit: sandstone and quartzite, stronglycurrent-bedded.

At its base, the Upper Estuarine Series rests upon theirregularly eroded surface of the Grey Limestone Series, as maybe well seen in the cliffs between Holbeck and White Nab,near Scarborough. This erosion does not appear to be of anygreat importance, however, and it seems probable that thestrong currents which brought in the sandy sediment of theMoor Grit merely scoured away the upper part of the newlydeposited marine muds below.

The Moor Grit is a comparatively pure quartz-rock, andalthough it contains abundant casts of logs and branches, itincludes no well preserved plant remains. It appears to representthe delta foreset beds which built up the Grey Limestone Seaapproximately to water level again.

The impure current-bedded sandstone above containslenticles of silt and sandy shale enclosing a few fossil plants,chiefly Ferns, and a few twigs of Conifers, all in a very fragmentary condition, but quite well preserved.

The level-bedded sandstones and shales which constitutethe upper part of the series, begin, in the Burniston and Scalbysection, with fissile, micaceous shales, whose bedding planes arecovered with leaves of Ginkgoales, pinnules of Ferns, twigs andcone scales of Conifers, mixed with seeds and other debris.These plant-beds appear to have been deposited in shallowbut extensive pools on the delta surface, and contain driftedmaterial only [4]. No Cycads have yet been discovered in thesebeds, and the flora is characterized by the abundance of Ginkgoales. It is interesting to find that several species, whichare found nowhere else in the Middle]urassie of Yorkshire, haveturned up in these drifted plant-beds, and suggest the presence

274 V. WILSON,

of a somewhat different flora further upstream . These alienspecies are all thick-cuticuled forms, allied to Th innfeldia and5ienopteris.

The Bennettitalean fronds and inflorescences of the UpperEs tua rine Series ha ve almost all been found in the sedimentsfilling distributary channels, and were probably washed into thestreams in times of flood. They all belong to species wellkn own in either the Middle or Lower Estuarine Series.

Another interesting type of drifted plant bed is provided bythe Ginkgoites beds and Baiera beds, which are fonnd in the coas tsection. The matrix is usually a laminated silt or sandstoneforming part of a channel-filling, crowded with the leaves of asingle species, almost to the exclusion of other plants. It isprobable that the Jurassic Ginkgoales were deciduous, as themodern Ginkgo biloba is, and that these richly fossiliferousdeposits were formed when the trees were shedding their leaves.

The principal level of channel erosion in the UpperEstuarine Series on the coast is about 70 feet above the GreyLimestone Series, and the maximum depth of erosion appearsto be about 20 feet.

IV. THE CORNBRASH AND UPPER JURASSIC ROCKS.By VERNON WILSON, PH.D., B.Sc., D.L e . , F.G.S.

The Cornbrash.During the gre ater part of the Middle Jurassic period it

has been shown that extensive deltaic conditions held sway,building up sediments to an extent only rivall ed by the Millstone Grit in Yorkshire. These deltaic conditions wereinterrupted at intervals by marine transgressions of shortduration , after each of which there was a reversion to deltaicconditions. These cha nges continued until the basin was almostsilted up and th e final , Callovian, transgression put an endto any further deltaic sedimentation.

During this final transgression there were deposited a fewfeet of beds classed on their faunal content as of Upper Cornbrashage, that is, belonging to the macrocephalus zone. The absencefrom them of fossils cha racteristic of the lower Cornbrashdivisions of other parts of England makes it difficult to det erminewhether or not part of these beds should be assigned to theLower Cornbrash.

The distribution and stratigraphy of the Cornbrash havebeen described at length by Fox-Strangways [12], and, morerecently, various sections have been re-described by Douglasand Ark ell [10 and 1]. Along the coast the Cornbrash firstoccurs as a thin , hard bed of impure dark gritty limestone at


about low-water mark in the Wyke, north of Filey Brigg. Ithas a thickness of It feet in the cliffs at Gristhorpe Bay, wherethe upper part of the bed is highly ferruginous, the upperlimit being marked by a dark mottled shale band which is crowdedwith crushed specimens of Microthyris lagenalis.

The bed is again seen for a considerable distance at thesouth end of Cayt on Ba y below Red Cliff, where its thicknessha s increased to zt feet; in the past this section has yielded themajority of the Cornbrash fossils recorded from the coast.North of Cayton Ba y the rock occurs in the cliff-top at Wheatcroft, and thereafter it passes inland, where its position hasbeen inferentially mapped at the base of the Kellaways Rock,westwards to Ryedale-a distance of about 30 miles. The oldSpring Hill Brick Pit (close to the Seamer Road Power Station,Scarborough) provides an excellent section of the Deltaic Beds,Cornbrash and Kellaways Rock; the Cornbrash is still a thickgritty limestone, blue in colour , but highly ferruginous in itsupper part and containing Lopha marshii, Osirea undosa andTrigonia scarburgensis in abundance.

The numerous consequent streams flowing southward fromthe moors have cut deeply through the Tabular Hills and it isin the gorges so formed that the finest inland exposures ofthe Cornbrash are found below the higher Jurassic strata. Itoccurs in Langdale Gorge in the Hackness Hills area ; in theupper reaches of Newtondale; near Lastingham ; in the sidesof Loskey and Hutton Becks ; and at other localities westwardtowards Bilsdale. In Newtondale the Cornbrash is 5 feetthick and consists of a lower mottled shelly red limestonecontaining Burmirhynchia fusca, Lopha marshii and Ostreaundosa, overlain by a black shelly limestone containing thesame fauna as the .lower bed along with numerous otherlam ellibranchs-Trigonia cassiope, T. scarburgensis, Oxtyomaexpansa, Lima rigidula and Chlamys anisopleurus. 'Vest ofBilsdale the Cornbrash has been recorded as a red ferruginousband in R yedale below the Kellaways Rock, and Dr. Versey [44]has recorded a thin ferruginous band in the same position nearKepwick, which he has referred to the Cornbrash. Several smalleroutliers of the Cornbrash occur scattered over the North Yorkshire Moors and it has an extensive outcrop around the base ofthe large Kellaways Rock outlier north of Eskdale, where itpossesses the characters of a sandy ferruginous marl and isalmost devoid of fossils.

From Kepwick southward along the western edge of theHambleton Hills, the Cornbrash has not been found and it istotally absent from the Howardian Hills to the south-east.

So far as is known at present the Yorkshire Cornbrashbelongs to the Microthyris lagenalis sub-zone. The commonlamellibranchs are the same as those occurring in the Upper

276 V. WILSON,

Upper Calcareous Grit.Osmington Oolite Series.Middle Calcareous Grit.Hambleton Oolite Series.Lower Calcareous Grit.

(b) Oxford Clay, including the Hackness Rock in the lower part.(a) Kellaways Rock.

Throughout this great mass of sediments the passage fromone division to the succeeding is in every case gradual, andeffected through a vertical span of a few feet. Lateralvariations in lithology are common and take place gradually;large and small scale thickenings and thinnings are also presentthroughout the whole series.

Cornbrash south of the Humber; but with the exception ofMicrothyris lagenalis the remainder of the characteristic UpperCornbrash brachiopods have not been recorded. The ammonitesalso are peculiar to Yorkshire, belonging to species not foundelsewhere. Neither Clydoniceratid ammonites nor any of theusual diagnostic Lower Cornbrash lamellibranchs and brachiopodshave been recorded so far from this province.

The Jurassic deposits occurring above the Corn brash comprisefour major divisions which conform to a rhythmic succession ofgrits and clays, and within one of these divisions-the CorallianSeries-a lesser grit-limestone rhythm is recognised. Thesuccession is as follows :-

(d) Kimeridge Clay.(c) Corallian Series

(a) The Kellaways Rock.The Kellaways Rock is the lowest member of the series,

consisting mostly of thick sandstones, usually soft, sandy andferruginous in the upper beds, while the basal beds are shales.The whole comprise 50-60 feet of sediments belonging to thekoenigi zone and possibly extending into the lower part of thecalloviense zone.

On the coast, the Kellaways Rock first appears above theCornbrash in Newbiggin Wyke, north of Filey Brigg ; it occupiesthe lower part of the cliffs around Gristhorpe Bay and its finestdevelopment is seen at Red Cliff at the northern end of theBay. Here, the 35 feet of Kellaways Rock consists of hard andsoft sandstones with about IS feet of shales forming the lowerpart, and judging from the fauna which these beds have yieldedin the past, they belong to the koenigi zone. Above, thereoccurs 19 feet of Hackness Rock beds, overlain by Oxford Clay,to the extent of about 120 feet, which is capped in the top ofthe cliff by the Lower Calcareous Grit. According to Dr. Spath[37J there is a non-sequence between the Kellaways and Hackness Rocks on the coast, the extent of which covers the absenceof the jason, pollux and castor zones and probably also includes


the upper part of the calloviense zone and some of the lowerpart of the aihleta zone; the precise extent of this gap is,however, unknown.

The Kellaways Rock is again seen in faulted positions atOsgodby Nab and below Scarborough Castle Hill where itconstitutes 51 feet of thickly-bedded barren sandstone. FromCayton Bay the outcrop strikes inland, passing into theHackness, Tabular and Hambleton Hills areas, and formingeasily discernible rounded buttresses below the fine dissectedseries of Lower Calcareous Grit escarpments. Its widest spreadoccurs over the Wykeham, Allerston, Saltersgate and PickeringMoors, being well exposed in the Derwent gorge at Langdaleand in the precipitous sides of Newtondale, where about 120-130feet of strata are made up of massive hard and soft sandstoneswith shales at the base; probably 30-40 feet of the upper bedsbelong to the Hackness Rock.

The Kellaways Rock underlies the Hambleton Hills, onthe western flanks of which it is occasionally seen where notobscured by the talus from the overlying deposits. At thefoot of Boltby Scar about 50 feet of hard and soft sandstonesare visible, the topmost bed being capped by a layer of Gryphmabilobata immediately followed by Oxford Clay shales. Farthersouth, similar beds occur below Whitestone Cliff, but here theOxford Clay is greatly attenuated; at Roulston Scar it isnot seen at all, the so-called Kellaways Rock being subjacentto the Lower Calcareous Grit. The extent to which the upperbeds of this Kellaways Rock represent an arenaceous development of the Oxford Clay is not known.

Subsidiary outliers of Kellaways Rock occur on HarwoodDale and Fylingdales Moors; but in north Cleveland to thenorth of Eskdale these rocks form large outliers on Brown Hill,Moorsholm, Danby Low, Lealholm and Roxby Hill Moorsextending from Girrick to Ugthorpe. In these areas the rockconsists, in the upper part, of hard siliceous sandstones containingabundant casts of belemnites; the lower beds are flaggy andcontain a fair number of quartz pebbles; towards the basethey become shaley.

In the Howardian Hills, the Kellaways Rock is represented by30-40 feet of soft friable yellow and white sands, containingoccasional ironstone nodules, streaks of ironstone andcarbonaceous fragments; otherwise it is devoid of fossils. Ithas a discontinuous faulted outcrop from Gilling Park throughHovingham Woods to Easthorpe Farm; it occurs between theCumhag and Owlers Woods at Castle Howard, and in thevicinity of High Hutton where, close to the River Derwent,about 40 feet of these sands are worked.

South-east of the Derwent, sporadic occurrences of thesesands occur in faulted positions in the vicinities of Eddlethorpe

V. WILSON,

Hall, Burythorpe, Leavening and Garrowby, the thicknessgradually diminishing and eventually thinning out completelytowards the Market Weighton axis. South of the MarketWeighton axis these loose sands again occur at Newbald andDrewton where, besides being highly micaceous, they haveyielded a fauna indicative of the koenigi and calloviense zones.

(b) The Oxford Clay (Yorkshire).This division in Yorkshire is not characterised by a solid

mass of clay as in other parts of the country, but consists oflower arenaceous beds-the Hackness Rock-overlain by loosegrey shales which extend up into the pracordatum zone. Theupper shales gradually take on a more sandy aspect beforepassing into the overlying Lower Calcareous Grit. Shales andclays constitute the greater part of this division in Gristhorpeand Cayton Bays; at Red Cliff the succession includes 19 feetof Hackness Rock overlain by about 130 feet of shales. AtScarborough Castle Hill the Hackness Rock has increased to25 feet, while the overlying shales are only a few feet less thantheir thickness at Red Cliff. In the past the ferruginous sandyand often oolitic beds (now classed as the Hackness Rock) haveyielded large numbers of ammonites, few of which were obtainedin situ. However excellent this material may be, it will benecessary to make new and more precise records and obtainnew material from these beds before dogmatising as to theirexact age, and before the extent of any faunal non-sequences canbe accurately appraised. Such a suggestion was put forwardby Hudleston in 1875, yet palseontologists continued to jugglewith this old material and uncertain records! Dr. Spath [37Jhas recently indicated the presence of a non-sequence at thebase of the Hackness Rock of the coast. The extent of thisbreak has already been considered, and on the ammonite evidencehe considers these beds to range, in age, from probably the upperpart of the athleta zone into the lamberti zone. The claysand shales above the Hackness Rock are un fossiliferous exceptfor a few feet at the base at Scarborough.

Inland, the vertical extent of the Hackness Rock is notknown; the Oxford Clays and Shales above it form a belt ofwet ground beneath the Lower Calcareous Grit escarpmentsfrom the coast westward to the Hambleton Hills. Throughoutthis distance their thickness diminishes to about 50 feet belowBlack Hambleton and they thin out completely farther southat Roulston Scar. The lowest few feet of these shales at BoltbyScar have recently yielded ammonites of undoubted renggeriage. The Oxford Clay soon reappears to the east of RoulstonScar and at Ampleforth is normally developed though onlyabout 40 feet thick.

In the Howardian Hills the Oxford Clay occurs below the

PROC. GEOL Assoc., V OL. XLV. (1934). PLATE 16.

A .-RoULSTON SCAR , WITH PART OF H OOD H rLL S EE N ON THE LEFT.

B .--THE ESCA RPMEN TS OF THE TAB U L AR HrLLs SEJ'N FROM ARDEN

:M OOR, N E A R H A WNBY.

[Pha ~os by V. W.

C .-THE LOWE R REACHES OF RV£DALE WITH THE RUHo/s OF RIEVAULX

ABBEY IN THE BACKGROUND.[To f '" p. z78.

SYXOPSIS OF J CRASSIC ROCKS OF YORKSHIRE. 279

l ower Calcareous Grit in Gilling Park, and from HovinghamHi gr \Vood to Easthorpe. It is repeated by a fault in theesca rpment alon g the west side of Castle Howard Park, andsmall faulted inliers occur between Castle Howard and theRiver Derwen t,

Recent road-workings near High Hutton have exposed thelowest beds of the Oxford Clay, above the Kellaways sands,and from these ammonites common to the renggeri zone havebeen obtained. Throughout this area the Oxford Clay is about60 to 70 feet thick ; east of the Derwent, however, it occurs atintervals and forms occasional low banks where it protrudesfrom beneath the Wolds. Down to Garrowbv its thicknesshas diminished to less than 20 feet, south of which it thins outcompletely towards the Market Weighton axis. An attenuatedthickness (about 50 feet) of Oxford Clay occurs to the south ofthe Market Weighton axis, the basal portion of which hasyielded ammonites belonging to the jason zone.

Dr. Spath [37J is of the opinion that, on the coast , the OxfordClay ends with the renggeri zone. In the Hambleton andHowardian Hills the clay extends higher than the renggeri zone,for fossils of this zone have been found in the basal beds inthese areas, and the writer is of the opinion that the upperlimit of the Oxford Clay for the Yorkshire basin reaches wellup in the prcecordatum zone.

(c) The Corallian SeriesThe argillaceous conditions of the Oxford Clay were ter

minated by an influx of fine arenaceous material. This influxmarks the beginning of the Lower Calcareous Grit deposition;that is, the lowest member of the Corallian Series, comprisingmany hundreds of feet of sandstones and oolitic limestones withtheir associated facies deposits.

The great spread of Corallian rocks ma y be convenientlydivided into the three topographic areas of the Tabular, Hambleton and Howardian Hills.

In the Tabular and Hambleton Hills areas the strike of therocks is generally E.-W., with a low dip to the south; whileintense faulting complicates the stratigraphy in the HowardianHills, the strike of the rocks is approximately E.S.E.-W.N.W.,with varying degrees of dip to the N.N.E.

Throughout the Tabular and Hambleton Hills , the harderbeds tend to weather out as plateaux showing a general increase inheight from the coastal districts westward to Black Hambleton,where 1 ,300 feet above sea level is attained. They are terminatedby ste ep banks or even precipices, giving a remarkable line ofE.. U' escarpments facin g the Cleveland Hills, the continuityJ 1 . ~ Ill:. ie. only broken by the numerous rivers and strea ms whichP ROC:. GEC L. Assoc ., V OL. XLV., PA RT 3. 1934 . 19

280 v. WILSON,

have excavated steep-sided gorges (Forge Valley, Newtondale,Ryedale, etc.), and flow southward into the Vale of Pickering.

Well-defined fault scarps occur on the north and southsides of the Coxwold-Gilling Gap, but the Gilling escarpmentdiminishes in boldness of outline towards Hovingham. To theimmediate south of Malton the Langton-Settrington ridgeconstitutes a lesser E.-W. escarpment by reason of the faultwhich defines it on the northern side.

Five of Arkell's six subdivisions of the British Coralliansuccession are recognised and are well developed in Yorkshire :

6. Upper Calcareous Grit, 30-80 feet.[5. Glos Oolite Series-best developed at Glos, Calvados ; in England

their most typical development is in Dorset, and part of theCoral Rag at Malton may be of this age.]

4. Osmington Oolite Series, 50-gO feet.3. Middle Calcareous Grit, 0-80 feet.

Confined to Yorkshire as an unfossiliferous gritstone, but represented by the fossiliferous Berkshire Oolite Series in the South.

2. Hambleton Oolite Series, 0-120 feet.Confined to Yorkshire where it is typically developed in theHambleton Hills.

I. Lower Calcareous Grit, 70-200 feet.

The' Grit' divisions are neither true grits nor true limestones,but are more correctly fine-grained calcareous gritstones.Variations in lithology occur in the gritstones and oolites, butthey are most marked in the latter, where there occur all thefacies associated with reefs. Changes in the nature and profusion of the faunas are also more pronounced in the ooliteperiods.

The Lower Calcareous Grit. The fine-grained gritstones,constituting this division, spread out from the coast aboutFiley through the Tabular Hills to the western escarpment ofthe Hambleton Hills overlooking the Vale of Mowbray; fromthere the outcrop swings south-eastwards, is broken by theCoxwold-Gilling Gap, and continues through the HowardianHills to the foot of the Chalk Wolds. These grits make upthe foundations of Filey Brigg below the level of the sea, andrise gradually from this position until they constitute the finecliffs between the Brigg and Gristhorpe Bay. Passing inlandthis grit plays the dominant role in the definition of a seriesof abrupt escarpments backing the Tabular and HambletonHills to the north. The passage from the Oxford Clay to theLower Calcareous Grit is best seen on the coast at GristhorpeBay; here the clay takes on a more sandy aspect in its upperpart, a change which becomes more pronounced until the overlying well-bedded gritstones are reached. This gradual changeis apparent throughout the Yorkshire basin, except in the southwest of the Hambleton Hills, where at Roulston Scar the grit-

PROe. GEOL. Assoc., VOL. XLV. (1934). PU.TE 17.

Unfra·red pkoto.

A.-THE COxwOLD-GILLING GAP SEEN FROM STONEGRAVE.

[PIt,,/os by V.W.

B.--GE:-IERAL VIEW NORTHWARD FROM GRISTHORPE BAY.

[To faa (>. 2"0.

SY~WPSIS OF JURASSIC ROCKS OF YORKSHIRE. z8r

stone lies directly on the Hackness Rock; here the Oxford Clayis absent.

The Lower Calcareous Grit has its maximum developmentin the Tabular and Hambleton Hills and thins out towards theMarket Weighton axis in the south, and to a lesser extenttowards the east. About 60-70 feet of these beds occur on thecoast; this thickness increases westward, 1Z0 feet being provedat Irton and probably a maximum of zoo feet occurs in thenorth Hambleton Hills. In the Howardian Hills the thicknessis about 60-70 feet, thinning off southward; 30 feet areknown at Acklam. A noticeable feature is the relatively rapidreduction in thickness from the northern part of the HambletonHills to the Coxwold-Gilling district and also from the HacknessHills to the coastal sections. In the former case the extentof this thinning amounts to about 130 feet in 9 miles and inthe second instance, some 7S feet in 6 miles. It is thought thatsome controlling factors must have influenced the sedimentationin these two areas. In the former example this influence may berelated to the Coxwold-Gilling faulting anomalies, which,according to Professor Kendall [25J, had affected the distributionof the Oxford Clay. Again, it has been shown how the PeakFault, on the coast, was moving during the deposition of theBlea Wyke Beds and the Dogger; and it is suggested that someactivity farther south along this line of weakness may havebeen initiated in post-Oxford Clay times and produced theeasterly thinning of the Lower Calcareous Grit.

The coastal sections north of Filey and at Scarboroughprovide the most complete succession, the details of whichmay be summarized as follows :-

it3, "The Ball Beds." Incoherent soft sandstone, very

ferruginous and containing large gritty limestonedoggers 10-18

2. Hard grey siliceous band 3-7I. Thick beds of hard buff gritstone having a siliceous cement;

this cement is concentrated in manv of the beds as smallmasses which weather out in irregular nodular bandsof a darker colour .. 40-45

This succession is traceable westward to Ryedale, but inihe escarpments north of Kirby Moorside and Helmsley the-!;fit becomes intensely siliceous, chert bands being frequent.This change is due to the abundance in western districts ofthe siliceous spicules of Rhaxella perforate, Hinde [21J. Inthe Howardian Hills the " Ball Beds" are not developed andin this region the grits show a variation from hard siliceousspicule-bearing rock in the west to gritty limestone-centredbeds and soft sandstone in the south-east.

The fauna of this lowest Corallian division is poor andiossils are scarce. In the past, however, fine specimens of

282 v. WILSON,

Aspidocerates and Cardiocerates have been collected. Amongother common fossils are Rhynchonelloidea thurmanni, Chlamysfibrosa, Exogyra nana, Gryphaa dilatata, Modiola bipariita,Pinna lanceolata, Trigonia triquetra, Collyrites bicordatus andNucleolites scutatus.

The Hambleton Oolite Series. This division for the mostpart consists of hard unfossiliferous oolitic limestones whichbecomes gradually replaced by gritty beds in the easterndistricts. The whole series of beds is lenticular in character,being thickest in the Kirby Moorside district. The rocks areconfined to the Tabular and Hambleton Hills, there being norecognisable representative of them in the Howardian Hills.The change from the Lower Calcareous Grit conditions to thesucceeding oolites was gradually effected; some indication ofthis impending change is seen in the" Ball Beds," for in themthe huge daggers are composed of impure limestone and thesucceeding basal beds of the oolites are hard impure sandy limestones, formerly classed by the Geological Survey [12, 13,14 and15] and others [5, 6, 20 and 22] as the' Passage' or ' Greystone'beds.

In the Filey district the uneven hard indurated characterof the lower Hambleton Oolite beds, with their equally unevenintercalated sandy partings, overlying the Lower CalcareousGrit, is taken to indicate intermittent intraformational erosionduring their deposition in this area. These beds, which are28 ft. thick at Filey, increase to about 54 feet at ScarboroughCastle Hill, of which the upper 26 feet are oolitic limestones andthe lower beds variable sandstones and harder detrital limestones.

In the Hackness Hills the upper oolites are 30 feet thickand below them occurs the famous Hambleton Oolite SpongeCoral reef from which all the Corallian sponges figured anddescribed by Hinde [21] were obtained. It is interesting to notethat in describing this reef as a " Spongite Coral Bed," WilliamSmith, in 1829 [35J was the only geologist to recognise thegreat role played by the sponges in the building of it. Thereef has a thickness of II feet and the most abundant fossilsfrom its numerous quarries include :-Holcospongia floriceps,Holcospongia polita, Peronidella recta, Thamnasircea concinna,I sastrcea explanata, Rhabdophyllia phillipsi, Chlamys fibrosa,Camptonectes lens, Ostrea quadrangularis, Geroillia aviculoides,Astarte ovata, Pseudomelania heddingtonensis, numerous speciesof Terebratulids, the Coral Fauna, and Cidarid spines. Theoccurrence of this reef at such a low horizon in the BritishCorallian sequence is unique; lithologically, it consists of anintimate mixture of masses of compound coral and spongesalong with the remainder of the fauna in a matrix of reefdetritus and fine mud.


In the Filey and Scarborough sections certain of the bedscan be correlated with the Hackness reef on the evidence ofstray reef sponges, rolled fragments of RhabdophylIia, Cidaridspines, and small Terebratulids. Another noticeable featureof these beds in the coastal sections is the profusion of oysters,Gryphaa dilatata, Exogyra nana and Lopha gregarea, and aprofusion of annelid incrustations, indicating shallow waterconditions in these parts.

Westward from Hackness and Forge Valley, the Hambletonoolites thicken and for the most part are unfossiliferous ; in thesewestern areas they become much more siliceous and oftenchert centres are developed through individual beds. Frequently, thin sections of these siliceous oolites and cherty bedsin the lower part of the series in the Hambleton Hills show aprofusion of the spicules of Rhaxella perforata, indicating thatthese organisms persisted for some time after the close of theLower Calcareous Grit episode in western districts. The normaloolites are usually un fossiliferous, but occasionally bands andthin streaks of shells and shelly material occur in the beds andfrom such occurrences, at Wydale, Thorntondale and Newtondale, many fossils have been obtained; commonly, Gervilliaaviculoides (large specimens), Trigonia spinifera, Astarte ovata,Exogyra nana, Chlamys fibrosa, Placunopsis radiata, Pseudomelania heddingtonensis and occasional Terebratulids.

The Middle Calcareous Grit. The oolitic limestones, coralreefs and associated deposits belonging to the Berkshire OolitePeriod in the Midlands are represented in Yorkshire by a seriesof sandstones, gritty limestones and impure oolites, designated"The Middle Calcareous Grits" by the Geological Survey;These Grits occur only in the Hambleton and Tabular Hills,where their thickness varies from 15 feet to 60 feet; they havethinned out completely before reaching the Howardian Hills.The fauna of this period, with the exception of the richTrigonia hudlestoni beds at Pickering, is scanty and poorlypreserved. Sandstones and gritty limestones of this age constitute a large part of Filey Brigg and in them the followingfossils are common :-Gervillia aviculoides, Trigonia hudlestoni,Astarte ovata, Pseudomonotis ovalis, Modiola bipartita, Exogyranana, Chlamys fibrosa, Pseudomelania heddingtonensis andspicules of Rhaxella perforata.

The maximum thickness of these grits occurs to the southwest of the River Rye, at Helmsley, where about 60 feet ofunfossiliferous ferruginous grits are developed; eastward theirthickness diminishes to 40 feet of gritty limestones and shellbeds-the Trigonia hudlestoni beds-at Pickering, and inForge Valley no more than 20 feet of impure gritty limestonesare of this age.

The impure blue limestones, fine calcareous gritstones and

V. WILSON,

extremely rich shell beds occurring III Neweondale, nearPickering, are referred to as the 'Trigonia hudlesioni Beds'on account of the profusion of that particular species alongwith other Trigonise. These beds are traceable westward inHutton Beck and to a lesser extent in the Seven Gorge atSinnington. The thin shell beds are variable in extent andtheir thickness varies up to 6 inches, and in places they mergeinto the surrounding rock.

Among the more commonly occurring fossils in these bedsthe following may be noted :-Trigonia hudlestoni, 1'. reticulata,T. pickeringensis, Gervillia aviculoides, Cucullcea coniracta,Exogyra nana, Lopha gregarea, Chlamys fibrosa, Opis phillipsi,Astarte ooata, Placunopsis radiata, Pseudomelania heddingtonensis, Nerincea visurgis and Cerithium muricatum.

In the impure oolites associated with these shell beds thereoccur occasional lumps of Thamnastrcea arachnoides, indicatingthat had the conditions been somewhat different in this area areef might have been initiated.

East of Pickering the Trigonia hudlestoni beds die out andat Brompton about IS feet of arenaceous oolites and currentbedded oolites represent the upper part of the Middle CalcareousGrit. The occurrence of spicules of Rhaxella perforata in thesebeds is noticeable for they are not found elsewhere in thisdivision; it is probable that the mixed areno-calcareous conditions in this locality was suited to a colony of these organisms.

The Osmington Oolite Series. The deposits included in thisdivision occur in all the three topographic regions recognisedfor the Corallian deposits in Yorkshire; they extend roundthe fringe of the Vale of Pickering from the coast westward tothe south Hambleton Hills and throughout the Howardian Hills.The lower beds are dominantly oolites, unfossiliferous in theirpurest form; these are overlain by a variety of facies collectivelyknown as the Coral Rag, the whole series amounting to anaverage of 60 feet. The lowest beds of the oolites are imperfectly exposed below the Drift on the south side of FileyCarr Naze; they are obscured inland as far as Seamerfrom where they are well developed along the southern flank ofthe Tahular Hills to Ryedale. South-eastward, they extendfrom Helmsley forming a low ridge-the Cauklass Promontoryprojecting into the Vale of Pickering as far as East Ness, beinglimited on the south side by the northern fault of the CoxwoldGilling Gap. The whole series has a magnificent developmentin the Howardian Hills, where it commences in the high plateauto the east of Gilling and its continuity to the Chalk Wolds isonly broken by the complicated faulting so characteristic ofthis area.

In the later stages of the Osmington Oolite period extensivereef development took place, the compound corals Isastrcea


and Thamnasiraa, along with Thecosmilia, Montlivaltia andseveral rarer forms, being responsible for this outburst oforganic activity : 'while, living a more or less restricted life inthe interstices of the reefs was the' Coral Fauna,' comprisingthe lamellibranchs Lima zonata, Chlamys natiheimensis,Lithophaga inclusa, Lopha gregarea and the small gastropodLittorina muricata, together with Cidaris florigemma and C.smithi, the remains of which occur in all the reef facies.

The Coral Rag and upper beds of the underlying oolitesform a crescentic outcrop with an average width of half a mile tothe immediate north of Seamer, Ayton and Brompton. In theIrton boring, 22 feet of massive Thamnastrsean reef rock hasbeen proved over 54 feet of un fossiliferous oolites [46J. A smalleroutlier of these rocks occurs in the neighbourhood of Hacknessand, when the section at Bell Heads is compared with a similarsection at Seamer, it is evident that in these two localities therewas an earlier coral growth at some short time prior to the finaland greatest outburst. At this earlier time no reef wasformed, but certain beds at the same horizon contain a fairprofusion of Thecosmilia annularis and Montlivaltia dispar,Lima zonata and Lithophaga inclusa heing also recorded. AboutII to 12 feet of fossiliferous limestones separate this earliergrowth from the main reef.

Previous writers have suggested that part of the mainCoral Rag in the Seamer-Ayton-Brompton district may be ofearlier date, a suggestion, however, which is not here maintained, for in this district two facies of the Rag can be defined.Firstly, there is the massive Thamnastrsean Reef proper carryingits reef fauna, and secondly, this reef was cut through at anearly stage in its growth by a channel, coincident with the lineof the road between East Ayton and Brompton. Into thischannel most of the reef detritus was washed and in theserough deposits are found the remains of rapacious and otherorganisms who preferred the deeper habitat.

Mention has already been made of the reef-dwelling fossils,and it will suffice to indicate a few of those forms found inthe channel deposits :-Bourguetia striata (very common andvery large), Pseudomelania heddingtonensis, Trochoiomatornatilis, Hemicidaris iniermedia, Cidaris smithi, Camptonecteslens, Pseudomonotis ovalis, Astarte ovata, Natica arguta, Exogyranana, and Navicula quadrisulcata. Eventually this channelbecame filled up and finally the reef grew over it.

At Brompton the Osmington Oolites are faulted out andonly come in again at Pickering, from thence their outcropextends through Kirby Moorside to Helmsley and into the southeastern part of the Hambleton Hills. Throughout this areathe lowest beds comprise about 9 feet of impure oolites, overlainby fine shelly oolites (the Pseudomelania Limestones) to a thick-

286 v. WILSON,

ness of from 18 to 20 feet; these are followed by argillaceouslimestones-the Pickering Limestones-which complete thesuccession at Pickering, farther westward their place is partiallytaken by the development of Coral Rag. West of Pickering theCoral Rag is characterised by the corals Thecosmilia annularis,Montlivaltia dispar and Rhabdopbyllia phillipsi, along with theusual reef-dwelling mollusca and other fossils; it seems probablethat unstable coral banks rather than true reefs existed inthese parts. In the south Hambleton Hills the Coral Rag,underlain by about 40 feet of oolites, extends from Oswaldkirkthrough the Cauklass Promontory to East Ness, and to thenorth of Oswaldkirk fine-grained argillaceous reef limestonescontaining stray reef fossils are the lateral equivalents of theCoral Rag between Helmsley and Sproxton. The charactersof the Coral Rag in this area are identical with those of theCoral Rag between Pickering and Helmsley.

The Osmington Oolites in the Howardian Hills have recentlybeen described in detail by the writer [47:1 and it will sufficehere to note that in this area Coral Rag occurs overlying ooliticlimestones, which in the vicinities of Appleton-le-Street and NorthGrimston are represented by impure marly oolites with intercalated marl bands (" The Urchin Dirt Beds") carrying a profusion of Nucleolites scutatus. The Coral Rag is well developedon the plateau to the south-east of Gilling ; between Hovinghamand Slingsby ; a small area on the north side of Malton; and inthe Langton-North Grimston ridge to the foot of the Chalkescarpment. A faulted mass of pure argillaceous limestonescarrying stray reef fossils occurs at Hildenley near Malton, andwas evidently derived from some nearby reef which has sincebeen removed.

The Upper Calcareous Grit. The Osmington Oolite periodclosed with a reversion to conditions sufficiently arenaceous tobe inimical to the continuance of coral growth, for the depositsof the succeeding period are well-bedded buff gritstones. Priorto the deposition of the arenaceous material, submarine erosionlevelled out the coral reefs and banks, and it is evident that inthis process the material, along with the finer incomingarenaceous material, was washed southward over the HowardianHills.

The present outcrop of the Upper Calcareous Grit is limited.It occurs intermittently capping some of the southern ridgesof the Tabular Hills; a continuous outcrop has been mapped fromPickering to Helmsley and in the south Hambleton Hills it iswell seen along the north side of the Cauklass promontory.In the above areas the rocks are fine-grained gritstones witha variable thickness (10 feet at Pickering) of sandy shales below,and though an impoverished fauna is to be expected,Gryp!zcea dilatata, Lucina aspera, Chlamys fibrosa, C. midas, and

SY);OPSIS OF Jl'RASSTC ROCKS OF YORKSHIRE. 287

Camptonecies lens are fairly common. Excellent sections ofthese beds occur at Pickering, in Hutton Beck, and in theNunnington Railway cutting; in all, the thick grits and sandyshales amount to 46 feet.

In the Howardian Hills deposits of this age are met within two localities at opposite extremities of the area; at SnapeHill, Kilburn, and at North Grimston. In both instancesthe rocks are fine-grained calcareous mudstones containingfew fossils. At North Grimston these beds are locally knownas the North Grimston Cementstones. On Snape Hillthey arefaulted against Lower Calcareous Grit and have an outcrop ofabout 100 yards in extent; they are 48 feet thick and consist ofhard and rather softer beds of fine calcareous mudstone, thoughthe upper 12 feet are more arenaceous and calcareous Rhaxellaspicules are frequent.

The cementstones form a low ridge between Langton andNorth Grimston Hill, the 36 feet of strata there visible havingyielded large numbers of Grypheea dilatata, including var.discoidea, together with Lucina aspera, Gervillia sulcaia,Pholadomya concentrica, Exogyra nana, and fragments of indeterminable ammonites and belemnites. Fox-Strangways [12Jestimated the full thickness of these beds hereabouts at between70 and 80 feet. Formerly their upper junction with the overlying Kimeridge Clay was considered to be an unconformity,but in this locality the passage was gradually effected, therebeing no evidence of an unconformity.

(d) Kimeridge Clay.The Kimeridge Clay underlies the broad, flat Vale of

Pickering, upwards of 400 feet of poorly fossiliferous shales andclay being present, covered by the alluvial deposits of LakePickering and by Drift at its eastern end and in part of theCoxwold-Gilling Gap.

On the coast, the Clay is frequently exposed below theever-changing Drift cliffs at the south end of Filey Bay.Heavy spring-tides strip the sand from the beach to reveala floor of Kimeridge Clay packed with septarian nodulesand broken belemnites. It is in this vicinity that the nonsequence between the Kimeridge Clays and succeeding SpeetonClays has been demonstrated at Speeton, representing theabsence of the uppermost part of the Kimeridge Clay, thewhole of the Portland, Purbeck, infra-Valanginian and lowestValanginian formations [36]. Along the northern fringe of theVale of Pickering, west of Brompton, isolated patches ofKimeridge Clay appear through the alluvium, and atSinnington, Hodge Beck and Hutton Beck they are seen overlying the Upper Calcareous Grit.

288 V. WILSON,

In these sections the lowest part consists of thinly bedded,brown, grey and mottled shales containing a fair profusion offragmentary belemnites together with Ostrea delta, Exogyranana and Serpulee , higher up, these shales give place to themore typical black shales and clays. The large faulted massof Kimeridge Clay in the Coxwold-Gilling Gap forms low,rounded hills and where the surface soil has slipped in placesthe underlying clay is seen to contain squashed specimens of'Ammonites biplex ' and occasional belemnite fragments.

In the Howardian Hills the clay is repeated in a smallfaulted inlier lying to the south-west of Malton where in theHildenley brickyard the presence of Ostrea delta and' Ammonitesmutabilis ' indicates a lower Kimeridgian age. South-eastof Malton the clay skirts round the lower slopes of the ChalkWolds from Wintringham southward to Acklam, and betweenNorth Grimston and Birdsall it forms a fairly wide spread ina faulted inlier; near the former locality it has yielded fossilsindicative of the rasenia zones.

South of Acklam the Kimeridge Clay is obscured by theCretaceous overlap and it thins out completely towards theMarket Weighton axis, south of which it is also missing asfar as Drewton and from there to the Humber uncertainKimeridge Clay is in direct contact with the attenuatedOxford Clay. The full extent of the attenuation of theKimeridge Clay over this region is not known and may neverbe revealed.

V. SUMMARY.By VERNON WILSON, Ph.D., B.Sc., D.Le., F.G.S.

In the foregoing pages, it has only been possible to givethe briefest outline of one of the most interesting and variedseries of sediments in the country. It remains to add a fewremarks on the conditions of sedimentation which producedthe innumerable variations in the lithology and fauna of theserocks.

The Lower Lias shales with their associated earthy and shellylimestone bands and numerous oyster beds were laid down ina quiet sheltered sea of no great depth. The sandstones, sandyshales and ironstones of the Middle Lias accumulated undersimilar conditions, though the concomitant influx of arenaceousmaterial suggests some slight rejuvenation of the rivers carryingsediment into the basin in these times. During the UpperLias episode the basin was fed by sluggish rivers which graduallyfilled it with a great thickness of shales. The environment atthis time may be paralleled with the anrerobic conditionsobtaining in the Black Sea, though the Yorkshire sea was muchmore shallow.

SY~OPSIS OF JURASSIC ROCKS OF YORKSHIRE. 2890

The increasing influx of arenaceous material towards theclose of the Lias heralded the extensive deltaic conditions whichheld sway throughout the Middle Jurassic period. During thisperiod vast quantities of sediment were carried into an almostcompletely filled basin by rivers flowing from the surroundingland areas to form extensive delta flats, which supported variedand luxuriant floras during the period.

Periodic marine incursions arrested these purely deltaicconditions from time to time and deposited thin bands oflimestone which contain the only faunal remains of this period.During Liassic times the Market Weighton area existed as ashallow marine ridge. Elevation took place along this line duringthe succeeding period, and Dr. Black has reason to believe thatthis area was elevated until it became a broad unsubmergedE.-W. ridge which persisted throughout Middle Jurassic time;and it seems probable that it continued to exist as a ridge,either just below or just above sea-level, during later episodesin the Upper Jurassic period. The Callovian transgressionbrought the deltaic conditions to a close, and the basin wasagain submerged. Throughout the subsequent deposition ofthe Kellaways Rock, Oxford Clay, and Corallian beds, gradualsubmergence kept pace with sedimentation. Towards theclose of the Corallian period the sea became sufficiently shallowand free from arenaceous material to allow of an extensivedevelopment of coral reefs and banks. Renewed submergenceand the influx of sandy material terminated the coral growth, andafter a relatively short period of arenaceous sedimentation (theUpper Calcareous Grit) the black Kimeridge Clay conditionspersisted until the end of the Jurassic period in Yorkshire.

VI. SELECTED BIBLIOGRAPHY.I. ARKELL, W. J. 1933. The Jurassic System in Great Britain.

Oxford.2. BARROW, G. 1888. The Geology of North Cleveland. Mem.

Ceol. Surv.3. BEILBY, E. M. 1930. The Market Weighton Axis in Middle

Jurassic Times. Trans. Leeds Geol, Soc., pt. xx., pp. 10-12.4. BLACK,:\1. 1929. Drifted Plant Beds of the Upper Estuarine

Series of Yorkshire. Quart. Journ. Ceol. Soc., lxxxv., pp. 389437·

5. BLAKE, J. F., and HUDLESTON, W. H. 1877. On the CorallianRocks of England. Quart. Journ. Ceol. Soc., vol. xxxiii., pp.260-4 05 .

6. . 1891. The Geology of the Country between Redcarand Bridlington. Proc. Ceol. Assoc., vol. xii., pp. II5-I42.

7. BRODRICK, H. 1909. Notes on Footprint Casts from the InferiorOolite near Whitby, Yorks. Proc. Liverpool Ceol. Soc., vol. X.,

pp. 327-335.

8. BUCKMAN, S. S. 1912. Ammonites from the Scarborough Limestone. Proc. Yorks. Ceol. Soc., xvii., p. 207.

29°

9·

10.

II

12.

16.

17·

18.

19·

20.21.

22.

23·

26.

27·

28.

29·

31.

32 .

33·

34·

v. WILSON,

BUCKMAN, S. S. 1915. A Palzeontological Classification of .thejurassic Rocks of the Whitby District. In" Ceplogy of Whitbyand Scarborough," znd ed., Mem. Geol. Sure,

DOUGLAS, j. A. and ARKELL, W. j. 1932. "the StratigraphicalDistribution of the Cornbrash, II. The North-Eastern Area.Quart. Journ. Geol, Soc., vol. lxxxviii., pp. II2-170.

ELGEE, F. 1913. The Moorlands of North-Eastern Yorkshire.8vo. London, A. Brown and Sons.

FOX-STRANGWAYS, C. 1892. The Jurassic Rocks of Britain, vol. i.Yorkshire. Mem. Geol. Surv.

and BARROW, G. 1882. The Geology of Whitby andScarborough. Mem, Geol. Surv.

---- and 1915. The Geology of Whitby and Scar-borough. Mem, Geol. Surv.

----, CAMERON, A. G. and BARROW, G. 1886. The Geologyof the country around Northallerton and Thirsk. Mem, Geol.Suru., pp. 47-51.

HALLIMOND, A. F. 1925. Iron Ores. Bedded Ores of England andWales. Petrography and Chemistry. Mem, Geol. Suru. Spec.Rept, on the Min. Res. of Gt. Britain.

HARGREAVES, ]. A. 1913. Fossil Footprints near Scarborough.Naturalist, Feb., p. 92.

HEPWORTH, E. 1923. The Estuarine Series of the YorkshireCoast. Trans. Leeds Geol. A ssoc., pt. xix., pp. 24-28.

HERRIES, R. S. 1906. The Geology of the Yorkshire Coast between Redcar and Robin Hood's Bay. Vol. xix., p. 410.

1910. East Yorkshire in Geology in the Field, vol. iii.HINDE, G. ]. 1887-1912. A Monograph of the British Fossil

Sponges. Mon. Pal. Soc.HUDLESTON, \V. H. 1876-8. The Yorkshire Oolites. Proc, Geol,

Assoc., vol. iii., pp. 283-333 ; vol. iv., pp. 334-400; vol. V., pp.407-497.

1880-1. Contributions to the Paleeontology of theYorkshire Oolites. Geol, Mag. dec. 2, vol. vii., pp. 241-8, 289-98,391-404, 481-8, 529-38; vol. viii., pp. 49-59, II9-3I.

KENDALL, P. F. 1905. Sub-Report on the Concealed Portion ofthe Coalfield of Yorkshire, Derbyshire and Nottinghamshire.Final Rep. of the Roy. Comm. on Coal Supplies, pt. ix., App. iii.,pp. 188- 205.

---- and WROOT, H. E. 1924. The Geology of Yorkshire.8vo. Printed for the Authors.

LAMPLUGH, G. W. 1922. On Differential Earth Movement in NorthEast Yorkshire during the Jurassic Period. Proc, Yorks. Geol;Soc., vol. xix., pp. 383-94.

LANE, G. j. 1910. Notes on the jurassic Flora of Cleveland.Proc, Cleveland Nat. Field Club, vol. ii., pt. 4, p. 206.

MACMILLAN, W. E. F. 1932. Notes on Dogger Horizons in NorthEast Yorkshire. Proc, Yorks Geol. Soc., vol. xxii., p. 122.

PHILLIPS, ]. 1829. Illustrations of the Geology of Yorkshire,Pt. i. The Yorkshire Coast,

RASTALL, R. H. 1905. The Blea Wyke Beds and Dogger in NorthEast Yorkshire. Quart. Journ. Geol, Soc., vol. lxi., pp. 441-457.

REED, F. R. C. 1901. The Geological History of the Rivers ofEast Yorkshire. Sedgwick Prize Essay.

RICHARDSON, L. H. 1912. The Lower Oolitic Rocks of Yorkshire.Proc, Yorks. Geol. SaG., vol. xvii., p. 184.

SEWARD, A. C. 1900. The jurassic Flora of the Yorkshire Coast.Cat. Mesoz. Plants. Brit. Mus.

SIMPSON,:\1. 1884. The Fossils of the Yorkshire Lias.

PROC. GEOL. Assoc ., VOL. XLV . (1934)· PLATE I t) .

DII

1/II II

/1II 11

/11/ 1/

1/ 11/1 '1

/I /1II

If II

/I/1

II Osmo/herleII

....OJlTH"..II

/1

1/

//

1/

II/1

IITwj " :> Ka" II

IIII"II II

"II

II/' II

II

"" II

" IIII II

" " E."in woldII

"" /I

"" /1

/IIII I

0 SI I

u

u

IIII ,. "

ALLUVIUM

C HAL K !-r-''-;-.......

LOWER CRETACEOUS

KIMERJDGE CLAY

CORALLIAN

OXFORD CLAY &KELLAWAYS ROCK

LOWER OOLITES ~~?:;;<~ ':.::.:.

LIAS~~JII

TRIASh i/

M AP S HOWING TH E D ISTRIBUTION OF TH E JURASSIC R OCKS IN YORKSHIRE.

To f ace p. 290.

SUMMER FIELD MEETING TO NORTH-EAST YORKSHIRE. 291

35. SMITH, W. 1829. Memoir on the Stratification of the HacknessHills in Fox-Strangways, Jurassic Rocks of Britain, pp. 507-16.

36. SPATH, L. F. 1924. On the Ammonites of the Speeton Clay and theSub-divisions of the Neocomian. Geol, Mag., vol. Ixi., pp. 73-89.

37. ----. 1933. Revision of the Jurassic Cephalopod Fauna ofKachh (Cutch) Ammonoidea. Part vi., Mem, Geol, Suru. India,N.S., vol. ix., Memoir NO.2, pp. 855-877.

38. THOMAS, H. HAMSHAW. 1913. (i) The Jurassic Plant Beds of Roseberry Topping. Naturalist, p. 198.

39. 1913. (ii) The Fossil Flora of the Cleveland District ofYorkshire. I.-The Flora of Marske Quarry. Quart. ]ourn.Geol, Soc., vol. lxix., p. 223.

40. . 1915. The Thinnjeldia Leaf-Bed of Roseberry Topping.Naturalist, p. 7.

41. . 1925. The Caytoniales, a New Group of AngiospermousPlants from the Jurassic of Yorkshire. Phil. Trans. Roy. Soc.,ser. B., ccxiii., pp. 299-363.

42. ----. 1933. On some Pteridospermous Plants from theMesozoic Rocks of South Africa. Phil. Trans. Roy. Soc., ser. B,ccxxii., pp. 193-265.

43. TONKS, L. H. 1923. Recent Notes on the Dogger Sandstone ofthe Yorkshire Coast. Trans. Leeds Geol, Assoc., pt. xix., pp.29-33·

44. VERSEY, H. C. 1928. Cornbrash at Kepwick, N.E. Yorkshire.Naturalist, pp. Il7-8.

45. . 1929· The Tectonic Structure of the Howardian Hillsand Adjacent Areas. Proc, 'Yorks. Geol, Soc., N.S., vol. xxi.,pp. 197- 227.

46. WILSON,. V. 1931. A Borehole Section in the Upper Jurassicat Irton, near Scarborough. Trans. Leeds Geol, Assoc., vol. v.,pt. i., pp. 20-2.

47. ----. 1933. The Corallian Rocks of the Howardian Hills(Yorkshire). Quarl. [owrn, Geol, Soc., vol. Ixxxix., pp. 480-508.

SUMMER FIELD MEETING TO NORTH-EASTYORKSHIRE.

August 9th to aoth, I934.

Report by the Directors: MAURICE BLACK, M.A., Ph.D.,F.G.S., J. E. HEMINGWAY, Ph.D., s.se., and VERC'iON WILSONPh.D., B.Sc., D.Le., F.G.S.

The purpose of this meeting was to study the stratigraphyof the Jurassic Rocks in North-East Yorkshire. F or the examination of the coast section during the earlier part of the meeting,the party made their headquarters at Whitby. Through thekindness of the Whitby Literary and Philosophical Society,the Museum was placed at the disposal of the Association forevening meetings. Mention should be made of the facilitiesoffered by the London and North-Eastern Railway, for theparty not only travelled by special coach from York to Whitby,but also used Weekly Holiday Season Tickets, which considerably reduced travelling expenses for the coast excursions.

a synopsis of the jurassic rocks of yorkshire

Documents