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New information on the Kimmeridge Clay of Yorkshire
New Information on the Kimmeridge Clay of Yorkshire by JOHN C. W. COPE Received 22 October 1973; taken as read 3 May 1974
CONTENTS I. 2.
page 211 213 213
INTRODUCTION DETAILS OF SECTIONS
(a) The Coast (b) The Vale of Pickering 3. 4.
THE KIMMERIDGIAN ZONES IN YORKSHIRE CONCLUSIONS ACKNOWLEDGMENTS REFERENCES
214 217
220 220 220
J. C. W. 1974. New Information on the Kimmeridge Clay of Yorkshire. Proc, Geol. Ass., 85 (2), 211-221. Two sections of the Kimmeridge Clay are recorded from the Vale of Pickering, and new ammonite records for the Yorkshire Kimmeridgian are given. Similarities are noted with other areas of Britain and with Greenland. It is suggested that the Pecttnatites hudlestoni Zone is absent in Yorkshire, and that proximity to the Market Weighton swell may have been responsible for this. The development of the Kimmeridgian zones in Yorkshire is summarised. Department 0/ Geology and Oceanography, University College 0/ Swansea, Singleton Park, Swansea, SA2 8PP.
COPE,
1. INTRODUCTION
the Kimmeridge Clay has an extensive outcrop, flooring the Vale of Pickering. The area to the south is formed of Cretaceous rocks, and these rise steeply to form the scarp face of the Chalk Wolds. To the north of the Vale, rising from beneath the Kimmeridge Clay, are the more resistant Corallian rocks which form the higher ground of the Tabular Hills. These Corallian rocks crop out again south of the tract of Kimmeridge Clay at the western end of the Vale of Pickering, to form the Howardian Hills. In spite of the extensive outcrop of the Kimmeridge Clay very little is known about it palaeontologicaIly, and its thickness in the Vale is not known with accuracy. However, the Fordon No.1 borehole, only a few kilometres to the south of the Vale, proved 385 m. (1280 ft.) of Kimmeridge Clay (Falcon & Kent, 1960, 29), and this thickness is probably representative for the region. The lack of knowledge about the formation stems from general1ack of exposure due to the thick drift mantling the area, in many places reaching
IN YORKSHIRE
211 PRoe. GEOL. ASS., VOL. 85, PART 2,1974
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JOHN C. W. COPE
212
30 m. or more. Even on the coast exposure is minimal, and it is generally only under very favourable conditions of beach sand and shingle that low reefs of Kimmeridge Clay are seen to crop out intermittently on the southern side of Filey Bay, below the Cretaceous Speeton Clay.
ZONE
SUBZONES
ROTUNDA PALLAS/O/DES PECTINATUS HUDLESTONI WHEATLEYENSIS SC/TULUS ELEGANS AUTISSIODORENS/S EUDOXUS MUTAB/LIS CYMODOCE BAYLEf
PARAVI GATUS EASTLECOTTENS/S ENCOMBENS/S REfS/FORMIS WHEATLEYENS/S SMEDMORENS/S NO EVIDENCE BASE"f"RESENTON COAS PROVED ON COAST GREEN LANE PIT & COAST GREAT EDSTONE PROVED IN MALTON REGION
( Many ammonites in old collections)
Fig. 1. Standard Zones and Subzones of the Kimmeridgian Stage. and their development in Yorkshire
From time to time over the past few years evidence has been obtained for several of the standard Kimmeridgian zones (Fig. 1). Some recent records of the Kimmeridge Clay of the region have been made by Callomon (in Callomon & Cope, 1971). As a result of a series of visits to the region, the author has been able to augment very substantially the collections on which these earlier identifications were made (University of Hull, Callomon and Donovan Collection, 1964).
KIMMERIDGE CLAY OF YORKSHIRE
213
2. DETAILS OF SECTIONS (a) The Coast A series of shales exposed in 1964 on the coast at Reighton (TA 143764) were measured, and their fauna described by Callomon (1971, 162). He recorded some 12 m, of shales, the upper half belonging to the Pectlnatites (Virgatosphinetoides) elegans Zone, and the lower to the Aulaeostephanus autissiodorensis Zone. A subsequent visit here by the writer showed a partially obscured section and only the autissiodorensis Zone was exposed at this point. The fauna obtained included A. autissiodorensis (Cotteau), A. volgensis (Vishniakoff), and abundant Propectinatites spp. The specimens of the latter genus are particularly interesting in that they include forms apparently intermediate between P. websteri Cope and early Peetinatites of the subgenus Arkellites. The author has yet to see true Pectinatites from the Lower Kimmeridgian, and it seems possible that the specimens recorded from this locality in the upper part of the autissiodorensis Zone by Callomon could have belonged to Propectinatites rather than to Peetinatites.
The highest apparent Kimmeridge Clay on the coast here has yielded Peetinatites (P.) proboscide (Buckman), signifying the presence of the P. (P.) peetinatus Zone. This is a higher horizon than any previously recorded
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JOHN C. W. COPE
from the coast, and I am indebted to Dr. P. Kaye who furnished me with the specimen mentioned above, obtained from immediately beneath the Speeton Clay. This horizon appears to correspond well with the highest Kimmeridgian recorded in the North Fordon (G3) borehole, and thus disproves the hypothesis that higher Jurassic horizons exist inland, beneath the Lower Cretaceous unconformity, than on the coast, as has been hitherto supposed (Falcon & Kent, 1960, 27). There is no evidence to suggest that the coastal succession up to this point, not seen at all in recent years, is incomplete. Evidence from inland discussed below, however, suggests that the P. (A.) hudlestoni Zone is probably absent here. (b) The Vale of Pickering
In the Vale of Pickering isolated brickpits have been worked, from time to time, in areas where the drift is thin. However, most of these have been long overgrown and published faunal lists are so vague as to be almost completely worthless. It is therefore interesting to record details of two pits opened relatively recently; one of them although disused is still useful, the other is worked intermittently and is at present disused. The first of the two pits is situated to the north of Marton, on the north side of Green Lane (SE 731837), and is hereafter referred to as the Green Lane Pit (Fig. 3). In this pit are exposed some 12 m. of highly bituminous shales. The pyrite in them has oxidised and the resulting selenite covers the bedding planes, making the shales very fissile. These shales are mostly too weathered to yield fossils, but a ferruginous calcareous siltstone interbedded in the shales 4 m. above the floor of the pit yields variably preserved, but generally readily identifiable, ammonites and other fossils. Masses of this hard band litter the floor of the pit, where they are weathering, and break up with a conchoidal fracture. The Callomon and Donovan Collection contains numerous ammonites from this bed, and Callomon has listed these (1971, 159). The author has made large collections from the bed, and has obtained specimens in many cases better and more completely preserved than their counterparts in the Callomon and Donovan Collection, and as a result has modified and supplemented the faunal list given by Callomon. The most abundant of the ammonites are species of the genus Amoeboceras. These include: Amoeboceras (Euprionoceras) sp., Amoeboceras (Amoebites) kitchini (Salfeld), Amoeboceras (Amoebites) elegans Spath, Amoeboceras (Amoebites) cf. beaugrandi (Sauvage), Amoeboceras (Hoplocardioceras) sp. aff. decipiens Spath. Associated with these are species of Aulacostephanus, including: Aulacostephanus (Aulacostephanus) pseudomutabilis anglicus (Steuer), Aulacostephanus (Aulacostephanoceras) volgensis (Vishniakoff), Aulacostephanus (Aulacostephanoceras) cf. undorae (Pavlow).
KIMMERIDGE CLAY OF YORKSHIRE
215
These species of Aulacostephanus establish with certainty that the beds in this pit lie within the Zone of Aulacostephanus eudoxus. Of particular interest in this connection is the occurrence of ammonites of the sub-genus Hoplocardioceras, until recently only known from East Greenland. In Greenland, Hoplocardioceras occurs together with other amoeboceratids in a series of otherwise un-ammonitiferous beds; the youngest ammonites known from the beds below belong to the mutabilis Zone, whilst the oldest above probably correlate with the wheatleyensis Zone (Cope, 1967, 73). Following the discovery of Hoplocardioceras in Yorkshire, the beds yielding
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JOHN C. W. COPE
this subgenus in Greenland may, as Callomon says (1971, 158), be safely dated as belonging to the eudoxus Zone. Another horizon in this pit which yielded ammonites was a hard silty shale, only 3 em. or so thick, again found in abundance in blocks on the pit floor, but also occurring in situ some 6 m. above the siltstone horizon. This shale yields crowds of the small amoeboceratid Nannocardioceras and includes Amoeboceras (Nannocardioceras) anglicum (Salfeld) and A. (N.) cf. krausei (Salfeld). In Dorset, some three metres above the Flats Stone Band is an identical fauna (Arkell, 1947,74, pl. IV, fig. 5), suggesting that the sudden appearance of these two species in such numbers forms an important marker horizon. This horizon was also discovered in the Warlingham borehole (Callomon & Cope, 1971,153) and named by Callomon therein the Nannocardioceras Beds (1971, 158). The second pit lies about one kilometre south of the Green Lane Pit, on one of the tracks leading to Rook Barugh, in the area known as Golden Hill (SE 725828), and is shown on Fig. 3. The following section was recorded: metres circa 1'0 Soil and weathered shale... Grey clay... 0·75 Stone band 0'5 Bituminous paper shale. Pectinatites (P). eastlecottensis (Salfeld) 0·4 0·2 Grey clay... Bituminous paper shale '" 0·15 Abrupt lithological change 12. Grey clay ... 0·2 11. Bituminous paper shale ... 0'12 10. Grey shale... 0·05 9. Bituminous shale ... 0·15 8. Hard pale grey mudstone. Abundant Pectinatites (Vtrgatosphinctoides) wheatleyensis 0·65 7. Black somewhat bituminous shale 0·08 6. Grey mudstone and shale. Abundant ammonite fragments and near base abundant P. (V.) wheatleyensis, both macroconch and horned microconch forms estimated 3·50 5. Dark shaly mudstone 0'45 4. Prominent rusty-weathering dark clay ... 0·6 3. Blue-black blocky clay with conchoidal fracture, P. (V.) clavelli, P. (V.) smedmorensis. 3·0 2. Rusty-weathering hard blue-black calcareous band ... 0·5 1. Blue-black clays, abundant P. (V.) clavelli, P. (V.) sp. indet. seen to 2·5
18. 17. 16. 15. 14. 13.
Because of the conchoidal fracture of some of these clays, and their closely spaced joints, fossils are not easy to obtain intact, and a plastercasting technique yields better material. Beds I to 8 clearly fall within the wheatleyensis Zone, the faunal associ"
KIMMERIDGE CLAY OF YORKSHIRE
217
ation of P. (V.) clavelli and P. (V.) smedmorensis being the characteristic faunal assemblage of the smedmorensis Subzone recorded from Dorset, the Warlingham borehole and the Wash area (Cope, 1974). The beds yielding P. (V.) wheatleyensis in like fashion suggest the presence of the wheatleyensis Subzone (Cope, 1974). The wheatleyensis Zone, therefore, is fairly complete here. According to the driver of an excavator operating in the pit on one visit, a few large uncrushed body-chambers of ammonites with strong ribbing had come from Bed 6 or thereabouts. These may well have belonged to P. (V.) grandis judging from their horizon and size. Between Beds 12 and 13 was a very abrupt lithological junction and the next bed yielding ammonites, Bed 15, produced abundant P. (P.) eastlecottensis, a form particularly characteristic of the lower part of the pectinatus Zone, now distinguished as the eastlecottensis Subzone (Cope, 1974). This strongly suggests that the lithological change between Beds 12 and 13 also marks a faunal break, and that the hudlestoni Zone is completely absent. Thus Beds 1-12 fall in the wheatleyensis Zone, and Beds 13-17 in the pectinatus Zone. The apparent absence of the hudlestoni Zone is somewhat surprising as the zone has hitherto been recorded in all Kimmeridgian sections and boreholes farther south, although in the Oxford and Swindon areas the Shotover Fine Sands have only been dubiously equated with this zone (Cope, 1967,71) as they have yielded no identifiable ammonites. The absence here of the hudlestoni Zone may possibly be due to the proximity of the Market Weighton swell, which was later the line of separation between the Speeton and Spilsby Lower Cretaceous basins. The relationship between these pits needs explanation. The Green Lane Pit is on high ground (presumably formed by the resistance of the highly bituminous shales there to erosion). To explain the occurrence of the higher zones to the south, in the Golden Hill area, in the absence of any strong dip in this direction, requires a strike fault running approximately through Marton village. The amount of throw is not readily determinable since the presence of the scitulus, elegans and autissiodorensis Zones has not been ascertained locally, but a minimum downthrow south of 30 m. is probably needed. 3. THE KIMMERIDGIAN ZONES IN YORKSHIRE No summary has been given of the Kimmeridgian in Yorkshire since Arkell wrote on the development of the zones of the Upper Jurassic there (1945). Since that time the scheme of Standard Kimmeridgian Zones has been considerably modified (Ziegler, 1962; Casey, 1967; Cope, 1967, 1974), and various new exposures have been recorded. Updated information follows below.
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JOHN C. W. COPE
Baylei and Cymodoce Zones
Nothing can be added to the records of Arkell (1945, 351-2) for these zones. Their presence has definitely been established in the Malton region, though earlier records from the coast most probably refer to material derived from local boulder clay. Mutabilis Zone
Mr. J. K. Wright has recently sent me some fragmentary specimens obtained from a shallow trench at Great Edstone (just to the west of the area shown in Fig. 3) (SE 706841). The ammonites, though fragmentary, are readily identifiable and include: Rasenia (Rasenioides) aff. thermarum (Oppel), Rasenia (Rasenioides) aff. lepidula (Oppel), Aulacostephanus (Aulacostephanoceras) cf. eulepidus (Schneid). The assemblage clearly belongs to the mutabilis Zone, and appears to be the first definite record of the zone in Yorkshire. Arkell (1945, 352) records Amoeboceras spp, from near Marton and suggested that they might have come from either the mutabilis or the (then existing) pseudomutabilis Zone. H seems likely, to judge from Arkell's description of the locality from whence the specimens came, that they were from the locality which was later the site ofthe Green Lane Pit, and are thus of eudoxus Zone age. Eudoxus Zone
The Green Lane Pit provides firm evidence for the eudoxus Zone in the Vale of Pickering. Coastal records of A. eudoxus, A. pseudomutabilis, and A. undorae (Arkell, 1945, 352) clearly require correlation with the eudoxus Zone. These must have come from horizons below those described by Callomon (1971, 162). Autissiodorensis Zone
This zone is well established from the coast, with the zonal index species occurring commonly, and accompanied by the microconch form A. volgensis (Vishniakoff). Callomon (1971, 162) recorded Subdichotomoceras in situ here, thus finally dispelling any remaining doubts that this genus is a lower Kimmeridgian form, and cannot be a Pavlovia from the Upper Kimmeridgian-a possibility suggested by Arkell (1945, 354). Elegans Zone
Callomon's record of this zone (1971, 162) is the only record of the zone in Yorkshire. As with other zones its thickness is not known accurately, but bearing in mind the thickness of the Kimmeridge Clay shown in the Fordon No.1 borehole (some 9 km. west of the coastal exposure) it would seem likely that the 6 m. of the zone recorded by Callomon represents only a part of the thickness of the zone.
KIMMERIDGE CLAY OF YORKSHIRE
219
No specimens of Gravesia have been recorded from Yorkshire, and Arkell's remark that Gravesia had been found in east Scotland, and thus could be present in Yorkshire (1945,353), is puzzling. It may be based on his reading of the account of the Kimmeridgian there by Bailey & Weir, in which they record the Gravesia zones (1932, 458). It is made clear in various places, however (e.g. 1932, 464), that this reference is based solely on other ammonites believed to be indicative of this zone. To the author's knowledge, the presence of Gravesia north of Swindon has yet to be confirmed. Scitulus Zone
This zone has yet to be recorded from Yorkshire, but there is no reason to suppose that it is absent. Indeed, thickness considerations of the whole formation suggest that it should be present. Wheatleyensis Zone
The Golden Hill Pit has furnished the first conclusive proof of the presence of this zone in the area. Arkell (1945,353) suggested that specimens of fine-ribbed perisphinctids from the coast should be correlated with this zone; he believed that this represented the highest Kimmeridgian zone of the coastal section, but the wheatleyensis Zone age of the specimens was never firmly established. Hudlestoni Zone
The zone appears to be absent in Yorkshire. However, only in one place (the Golden Hill brickpit described above) is there a well-exposed section of the beds around this horizon. There is no evidence thus far to suggest much lateral variation in the Kimmeridgian of Yorkshire, and on this basis it seems probable that the absence of the zone is a regional phenomenon. Pectinatus Zone
Faunas of the pectinatus Zone have been definitely identified on the coast, in the North Fordon (G 3) borehole and in the Vale of Pickering. This zone is therefore one of the most widely recorded of the Kimmeridgian zones in Yorkshire. Pallasioides and Rotunda Zones
No record of higher zones than the pectinatus Zone has been made in Yorkshire, and everywhere the Lower Cretaceous rocks appear to rest on horizons up to the pectinatus Zone. Unlike Lincolnshire and areas farther south, there is no evidence of later Jurassic rocks than this. Fragments of ammonites, rolled and phosphatised, occurring in the Speeton Clay Co pro-
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JOHN C. W. COPE
lite Bed may, however, include species of Pav/ovia, but positive identification is impossible. The possibility remains that these later Kimmeridgian zones were deposited, but were subsequently eroded before the advent of the Lower Cretaceous marine incursion. 4. CONCLUSIONS The development of the Kimmeridge Clay in Yorkshire is in some respects unique. There are few regions where the formation is as thickly developed as here, and if the uppermost zones had been as well developed here as in Dorset, the thickness would have similar to that of the typesection. This is all the more surprising when it is realised that the hud/estoni Zone, one of the thickest zones in the Dorset section, is absent in Yorkshire. The lithological types encountered in the Kimmeridge Clay of Yorkshire are the same as those obtaining in Dorset and in the Warlingham borehole; but unlike other sections showing some breaks in the succession, for example the Oxford or Swindon areas, no arenaceous horizons are developed. The ammonite faunas show great similarity with those of Kimmeridgian age farther south. The presence of commonly occurring specimens of the genus Subdichotomoceras in the autissiodorensis Zone is about the only distinguishing feature of these Yorkshire faunas. This genus has not, with any certainty, been recorded farther south in Britain. There is still a great deal to be learned about the Kimmeridge Clay of Yorkshire, but the nature of the ground suggests that surface exposures alone will not provide all the answers ; for this, a number of large diameter cored boreholes would be needed. ACKNOWLEDGMENTS I should like to record my gratitude to all who have contributed, in one way or another, to this work. In particular, I wish to thank Dr. J. H. Callomon for information on the Yorkshire exposures and many valuable discussions; the Department of Geology of the University of Hull for the loan of the Callomon and Donovan Collection; and Mr. J. A. Crossley, of Crossley Building Products Ltd., for permission to collect from the Golden Hill Pit. For donation of ammonites I thank Dr. P. Kaye and Mr . J. K. Wright. REFERENCES W. J. 1945. The Zones of the Upper Jurassic of Yorkshire. Proc. Yorks . geol. Soc ., 25, 339-58. - - -. 1947. The Geology of the Country around Weymouth, Swanagc, Corfe, and Lu1worth. Mem , geol. Sur v, U.K. 386pp. ARKELL,
KIMMERIDGE CLAY OF YORKSHIRE
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BAILEY, E. B. & J. WEIR. 1932. Submarine Faulting in Kimmeridgian Times in East Sutherland. Trans. R. Soc. Edinb., 57, 429-67. CALLOMON, J. H. & J. C. W. COPE. 1971. The Stratigraphy and Ammonite Succession of the Oxford and Kimmeridge Clays in the Warlingham Borehole. Bull. geol, Surv, Gr. sr., 36, 147-76. CASEY, R. 1967. The Position of the Middle Volgian in the English Jurassic. Proc. geol. Soc., 1640, 128-33. COPE, J. C. W. 1967. The Palaeontology and Stratigraphy of the Lower Part of the Upper Kimmeridge Clay of Dorset. Bull. Br. Mus. nat. Hist. (Geo!.), 15, 1-79. - - - - . 1968. Propectinatites, a New Lower Kimmeridgian Ammonite Genus. Palaeontology, 11, 16-18. ----.1974. The Upper Kimmeridgian Ammonite Faunas of the Wash Area Boreholes, and a Subzonal Scheme for the Lower Part of the Upper Kimmeridgian. Bull. geol, Surv, oi. Br., 47, 29-37. FALCON, N. L. & KENT, P. E. 1960. Geological Results of Petroleum Exploration in Britain 1945-57. Memoir No.2, Geol. Soc. Lond, SPATH, L. F. 1935. The Upper Jurassic Invertebrate Faunas of Cape Leslie, Milne Land, I. Oxfordian and Lower Kimmeridgian. Meddr Grenland, 99 (2) 1-82. ----.1936. The Upper Jurassic Invertebrate Faunas of Cape Leslie, Milne Land, II. Upper Kimmeridgian and Portlandian. Meddr Grenland, 99 (3), 1-180. ZIEGLER, B. 1962. Die Ammoniten-Gattung Aulacostephanus im Oberjura, (Taxionowie, Statigraphie, Biologic). Palaeontographica, A 119,1-172.
CONTENTS I. 2.
page 211 213 213
INTRODUCTION DETAILS OF SECTIONS
(a) The Coast (b) The Vale of Pickering 3. 4.
THE KIMMERIDGIAN ZONES IN YORKSHIRE CONCLUSIONS ACKNOWLEDGMENTS REFERENCES
214 217
220 220 220
J. C. W. 1974. New Information on the Kimmeridge Clay of Yorkshire. Proc, Geol. Ass., 85 (2), 211-221. Two sections of the Kimmeridge Clay are recorded from the Vale of Pickering, and new ammonite records for the Yorkshire Kimmeridgian are given. Similarities are noted with other areas of Britain and with Greenland. It is suggested that the Pecttnatites hudlestoni Zone is absent in Yorkshire, and that proximity to the Market Weighton swell may have been responsible for this. The development of the Kimmeridgian zones in Yorkshire is summarised. Department 0/ Geology and Oceanography, University College 0/ Swansea, Singleton Park, Swansea, SA2 8PP.
COPE,
1. INTRODUCTION
the Kimmeridge Clay has an extensive outcrop, flooring the Vale of Pickering. The area to the south is formed of Cretaceous rocks, and these rise steeply to form the scarp face of the Chalk Wolds. To the north of the Vale, rising from beneath the Kimmeridge Clay, are the more resistant Corallian rocks which form the higher ground of the Tabular Hills. These Corallian rocks crop out again south of the tract of Kimmeridge Clay at the western end of the Vale of Pickering, to form the Howardian Hills. In spite of the extensive outcrop of the Kimmeridge Clay very little is known about it palaeontologicaIly, and its thickness in the Vale is not known with accuracy. However, the Fordon No.1 borehole, only a few kilometres to the south of the Vale, proved 385 m. (1280 ft.) of Kimmeridge Clay (Falcon & Kent, 1960, 29), and this thickness is probably representative for the region. The lack of knowledge about the formation stems from general1ack of exposure due to the thick drift mantling the area, in many places reaching
IN YORKSHIRE
211 PRoe. GEOL. ASS., VOL. 85, PART 2,1974
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JOHN C. W. COPE
212
30 m. or more. Even on the coast exposure is minimal, and it is generally only under very favourable conditions of beach sand and shingle that low reefs of Kimmeridge Clay are seen to crop out intermittently on the southern side of Filey Bay, below the Cretaceous Speeton Clay.
ZONE
SUBZONES
ROTUNDA PALLAS/O/DES PECTINATUS HUDLESTONI WHEATLEYENSIS SC/TULUS ELEGANS AUTISSIODORENS/S EUDOXUS MUTAB/LIS CYMODOCE BAYLEf
PARAVI GATUS EASTLECOTTENS/S ENCOMBENS/S REfS/FORMIS WHEATLEYENS/S SMEDMORENS/S NO EVIDENCE BASE"f"RESENTON COAS PROVED ON COAST GREEN LANE PIT & COAST GREAT EDSTONE PROVED IN MALTON REGION
( Many ammonites in old collections)
Fig. 1. Standard Zones and Subzones of the Kimmeridgian Stage. and their development in Yorkshire
From time to time over the past few years evidence has been obtained for several of the standard Kimmeridgian zones (Fig. 1). Some recent records of the Kimmeridge Clay of the region have been made by Callomon (in Callomon & Cope, 1971). As a result of a series of visits to the region, the author has been able to augment very substantially the collections on which these earlier identifications were made (University of Hull, Callomon and Donovan Collection, 1964).
KIMMERIDGE CLAY OF YORKSHIRE
213
2. DETAILS OF SECTIONS (a) The Coast A series of shales exposed in 1964 on the coast at Reighton (TA 143764) were measured, and their fauna described by Callomon (1971, 162). He recorded some 12 m, of shales, the upper half belonging to the Pectlnatites (Virgatosphinetoides) elegans Zone, and the lower to the Aulaeostephanus autissiodorensis Zone. A subsequent visit here by the writer showed a partially obscured section and only the autissiodorensis Zone was exposed at this point. The fauna obtained included A. autissiodorensis (Cotteau), A. volgensis (Vishniakoff), and abundant Propectinatites spp. The specimens of the latter genus are particularly interesting in that they include forms apparently intermediate between P. websteri Cope and early Peetinatites of the subgenus Arkellites. The author has yet to see true Pectinatites from the Lower Kimmeridgian, and it seems possible that the specimens recorded from this locality in the upper part of the autissiodorensis Zone by Callomon could have belonged to Propectinatites rather than to Peetinatites.
The highest apparent Kimmeridge Clay on the coast here has yielded Peetinatites (P.) proboscide (Buckman), signifying the presence of the P. (P.) peetinatus Zone. This is a higher horizon than any previously recorded
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JOHN C. W. COPE
from the coast, and I am indebted to Dr. P. Kaye who furnished me with the specimen mentioned above, obtained from immediately beneath the Speeton Clay. This horizon appears to correspond well with the highest Kimmeridgian recorded in the North Fordon (G3) borehole, and thus disproves the hypothesis that higher Jurassic horizons exist inland, beneath the Lower Cretaceous unconformity, than on the coast, as has been hitherto supposed (Falcon & Kent, 1960, 27). There is no evidence to suggest that the coastal succession up to this point, not seen at all in recent years, is incomplete. Evidence from inland discussed below, however, suggests that the P. (A.) hudlestoni Zone is probably absent here. (b) The Vale of Pickering
In the Vale of Pickering isolated brickpits have been worked, from time to time, in areas where the drift is thin. However, most of these have been long overgrown and published faunal lists are so vague as to be almost completely worthless. It is therefore interesting to record details of two pits opened relatively recently; one of them although disused is still useful, the other is worked intermittently and is at present disused. The first of the two pits is situated to the north of Marton, on the north side of Green Lane (SE 731837), and is hereafter referred to as the Green Lane Pit (Fig. 3). In this pit are exposed some 12 m. of highly bituminous shales. The pyrite in them has oxidised and the resulting selenite covers the bedding planes, making the shales very fissile. These shales are mostly too weathered to yield fossils, but a ferruginous calcareous siltstone interbedded in the shales 4 m. above the floor of the pit yields variably preserved, but generally readily identifiable, ammonites and other fossils. Masses of this hard band litter the floor of the pit, where they are weathering, and break up with a conchoidal fracture. The Callomon and Donovan Collection contains numerous ammonites from this bed, and Callomon has listed these (1971, 159). The author has made large collections from the bed, and has obtained specimens in many cases better and more completely preserved than their counterparts in the Callomon and Donovan Collection, and as a result has modified and supplemented the faunal list given by Callomon. The most abundant of the ammonites are species of the genus Amoeboceras. These include: Amoeboceras (Euprionoceras) sp., Amoeboceras (Amoebites) kitchini (Salfeld), Amoeboceras (Amoebites) elegans Spath, Amoeboceras (Amoebites) cf. beaugrandi (Sauvage), Amoeboceras (Hoplocardioceras) sp. aff. decipiens Spath. Associated with these are species of Aulacostephanus, including: Aulacostephanus (Aulacostephanus) pseudomutabilis anglicus (Steuer), Aulacostephanus (Aulacostephanoceras) volgensis (Vishniakoff), Aulacostephanus (Aulacostephanoceras) cf. undorae (Pavlow).
KIMMERIDGE CLAY OF YORKSHIRE
215
These species of Aulacostephanus establish with certainty that the beds in this pit lie within the Zone of Aulacostephanus eudoxus. Of particular interest in this connection is the occurrence of ammonites of the sub-genus Hoplocardioceras, until recently only known from East Greenland. In Greenland, Hoplocardioceras occurs together with other amoeboceratids in a series of otherwise un-ammonitiferous beds; the youngest ammonites known from the beds below belong to the mutabilis Zone, whilst the oldest above probably correlate with the wheatleyensis Zone (Cope, 1967, 73). Following the discovery of Hoplocardioceras in Yorkshire, the beds yielding
TO KIRKBY MILLS ~
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,r I
GOLDEN 'i UP.or HILL CIKimmeridge II
Clay
II II
"II MILES
o
I
o
i~
" KILOMETRES
Fig. 3. Detailed locality map showing locations of the two brick pits. The area covered is indicated by the square in Fig. 2
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JOHN C. W. COPE
this subgenus in Greenland may, as Callomon says (1971, 158), be safely dated as belonging to the eudoxus Zone. Another horizon in this pit which yielded ammonites was a hard silty shale, only 3 em. or so thick, again found in abundance in blocks on the pit floor, but also occurring in situ some 6 m. above the siltstone horizon. This shale yields crowds of the small amoeboceratid Nannocardioceras and includes Amoeboceras (Nannocardioceras) anglicum (Salfeld) and A. (N.) cf. krausei (Salfeld). In Dorset, some three metres above the Flats Stone Band is an identical fauna (Arkell, 1947,74, pl. IV, fig. 5), suggesting that the sudden appearance of these two species in such numbers forms an important marker horizon. This horizon was also discovered in the Warlingham borehole (Callomon & Cope, 1971,153) and named by Callomon therein the Nannocardioceras Beds (1971, 158). The second pit lies about one kilometre south of the Green Lane Pit, on one of the tracks leading to Rook Barugh, in the area known as Golden Hill (SE 725828), and is shown on Fig. 3. The following section was recorded: metres circa 1'0 Soil and weathered shale... Grey clay... 0·75 Stone band 0'5 Bituminous paper shale. Pectinatites (P). eastlecottensis (Salfeld) 0·4 0·2 Grey clay... Bituminous paper shale '" 0·15 Abrupt lithological change 12. Grey clay ... 0·2 11. Bituminous paper shale ... 0'12 10. Grey shale... 0·05 9. Bituminous shale ... 0·15 8. Hard pale grey mudstone. Abundant Pectinatites (Vtrgatosphinctoides) wheatleyensis 0·65 7. Black somewhat bituminous shale 0·08 6. Grey mudstone and shale. Abundant ammonite fragments and near base abundant P. (V.) wheatleyensis, both macroconch and horned microconch forms estimated 3·50 5. Dark shaly mudstone 0'45 4. Prominent rusty-weathering dark clay ... 0·6 3. Blue-black blocky clay with conchoidal fracture, P. (V.) clavelli, P. (V.) smedmorensis. 3·0 2. Rusty-weathering hard blue-black calcareous band ... 0·5 1. Blue-black clays, abundant P. (V.) clavelli, P. (V.) sp. indet. seen to 2·5
18. 17. 16. 15. 14. 13.
Because of the conchoidal fracture of some of these clays, and their closely spaced joints, fossils are not easy to obtain intact, and a plastercasting technique yields better material. Beds I to 8 clearly fall within the wheatleyensis Zone, the faunal associ"
KIMMERIDGE CLAY OF YORKSHIRE
217
ation of P. (V.) clavelli and P. (V.) smedmorensis being the characteristic faunal assemblage of the smedmorensis Subzone recorded from Dorset, the Warlingham borehole and the Wash area (Cope, 1974). The beds yielding P. (V.) wheatleyensis in like fashion suggest the presence of the wheatleyensis Subzone (Cope, 1974). The wheatleyensis Zone, therefore, is fairly complete here. According to the driver of an excavator operating in the pit on one visit, a few large uncrushed body-chambers of ammonites with strong ribbing had come from Bed 6 or thereabouts. These may well have belonged to P. (V.) grandis judging from their horizon and size. Between Beds 12 and 13 was a very abrupt lithological junction and the next bed yielding ammonites, Bed 15, produced abundant P. (P.) eastlecottensis, a form particularly characteristic of the lower part of the pectinatus Zone, now distinguished as the eastlecottensis Subzone (Cope, 1974). This strongly suggests that the lithological change between Beds 12 and 13 also marks a faunal break, and that the hudlestoni Zone is completely absent. Thus Beds 1-12 fall in the wheatleyensis Zone, and Beds 13-17 in the pectinatus Zone. The apparent absence of the hudlestoni Zone is somewhat surprising as the zone has hitherto been recorded in all Kimmeridgian sections and boreholes farther south, although in the Oxford and Swindon areas the Shotover Fine Sands have only been dubiously equated with this zone (Cope, 1967,71) as they have yielded no identifiable ammonites. The absence here of the hudlestoni Zone may possibly be due to the proximity of the Market Weighton swell, which was later the line of separation between the Speeton and Spilsby Lower Cretaceous basins. The relationship between these pits needs explanation. The Green Lane Pit is on high ground (presumably formed by the resistance of the highly bituminous shales there to erosion). To explain the occurrence of the higher zones to the south, in the Golden Hill area, in the absence of any strong dip in this direction, requires a strike fault running approximately through Marton village. The amount of throw is not readily determinable since the presence of the scitulus, elegans and autissiodorensis Zones has not been ascertained locally, but a minimum downthrow south of 30 m. is probably needed. 3. THE KIMMERIDGIAN ZONES IN YORKSHIRE No summary has been given of the Kimmeridgian in Yorkshire since Arkell wrote on the development of the zones of the Upper Jurassic there (1945). Since that time the scheme of Standard Kimmeridgian Zones has been considerably modified (Ziegler, 1962; Casey, 1967; Cope, 1967, 1974), and various new exposures have been recorded. Updated information follows below.
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JOHN C. W. COPE
Baylei and Cymodoce Zones
Nothing can be added to the records of Arkell (1945, 351-2) for these zones. Their presence has definitely been established in the Malton region, though earlier records from the coast most probably refer to material derived from local boulder clay. Mutabilis Zone
Mr. J. K. Wright has recently sent me some fragmentary specimens obtained from a shallow trench at Great Edstone (just to the west of the area shown in Fig. 3) (SE 706841). The ammonites, though fragmentary, are readily identifiable and include: Rasenia (Rasenioides) aff. thermarum (Oppel), Rasenia (Rasenioides) aff. lepidula (Oppel), Aulacostephanus (Aulacostephanoceras) cf. eulepidus (Schneid). The assemblage clearly belongs to the mutabilis Zone, and appears to be the first definite record of the zone in Yorkshire. Arkell (1945, 352) records Amoeboceras spp, from near Marton and suggested that they might have come from either the mutabilis or the (then existing) pseudomutabilis Zone. H seems likely, to judge from Arkell's description of the locality from whence the specimens came, that they were from the locality which was later the site ofthe Green Lane Pit, and are thus of eudoxus Zone age. Eudoxus Zone
The Green Lane Pit provides firm evidence for the eudoxus Zone in the Vale of Pickering. Coastal records of A. eudoxus, A. pseudomutabilis, and A. undorae (Arkell, 1945, 352) clearly require correlation with the eudoxus Zone. These must have come from horizons below those described by Callomon (1971, 162). Autissiodorensis Zone
This zone is well established from the coast, with the zonal index species occurring commonly, and accompanied by the microconch form A. volgensis (Vishniakoff). Callomon (1971, 162) recorded Subdichotomoceras in situ here, thus finally dispelling any remaining doubts that this genus is a lower Kimmeridgian form, and cannot be a Pavlovia from the Upper Kimmeridgian-a possibility suggested by Arkell (1945, 354). Elegans Zone
Callomon's record of this zone (1971, 162) is the only record of the zone in Yorkshire. As with other zones its thickness is not known accurately, but bearing in mind the thickness of the Kimmeridge Clay shown in the Fordon No.1 borehole (some 9 km. west of the coastal exposure) it would seem likely that the 6 m. of the zone recorded by Callomon represents only a part of the thickness of the zone.
KIMMERIDGE CLAY OF YORKSHIRE
219
No specimens of Gravesia have been recorded from Yorkshire, and Arkell's remark that Gravesia had been found in east Scotland, and thus could be present in Yorkshire (1945,353), is puzzling. It may be based on his reading of the account of the Kimmeridgian there by Bailey & Weir, in which they record the Gravesia zones (1932, 458). It is made clear in various places, however (e.g. 1932, 464), that this reference is based solely on other ammonites believed to be indicative of this zone. To the author's knowledge, the presence of Gravesia north of Swindon has yet to be confirmed. Scitulus Zone
This zone has yet to be recorded from Yorkshire, but there is no reason to suppose that it is absent. Indeed, thickness considerations of the whole formation suggest that it should be present. Wheatleyensis Zone
The Golden Hill Pit has furnished the first conclusive proof of the presence of this zone in the area. Arkell (1945,353) suggested that specimens of fine-ribbed perisphinctids from the coast should be correlated with this zone; he believed that this represented the highest Kimmeridgian zone of the coastal section, but the wheatleyensis Zone age of the specimens was never firmly established. Hudlestoni Zone
The zone appears to be absent in Yorkshire. However, only in one place (the Golden Hill brickpit described above) is there a well-exposed section of the beds around this horizon. There is no evidence thus far to suggest much lateral variation in the Kimmeridgian of Yorkshire, and on this basis it seems probable that the absence of the zone is a regional phenomenon. Pectinatus Zone
Faunas of the pectinatus Zone have been definitely identified on the coast, in the North Fordon (G 3) borehole and in the Vale of Pickering. This zone is therefore one of the most widely recorded of the Kimmeridgian zones in Yorkshire. Pallasioides and Rotunda Zones
No record of higher zones than the pectinatus Zone has been made in Yorkshire, and everywhere the Lower Cretaceous rocks appear to rest on horizons up to the pectinatus Zone. Unlike Lincolnshire and areas farther south, there is no evidence of later Jurassic rocks than this. Fragments of ammonites, rolled and phosphatised, occurring in the Speeton Clay Co pro-
220
JOHN C. W. COPE
lite Bed may, however, include species of Pav/ovia, but positive identification is impossible. The possibility remains that these later Kimmeridgian zones were deposited, but were subsequently eroded before the advent of the Lower Cretaceous marine incursion. 4. CONCLUSIONS The development of the Kimmeridge Clay in Yorkshire is in some respects unique. There are few regions where the formation is as thickly developed as here, and if the uppermost zones had been as well developed here as in Dorset, the thickness would have similar to that of the typesection. This is all the more surprising when it is realised that the hud/estoni Zone, one of the thickest zones in the Dorset section, is absent in Yorkshire. The lithological types encountered in the Kimmeridge Clay of Yorkshire are the same as those obtaining in Dorset and in the Warlingham borehole; but unlike other sections showing some breaks in the succession, for example the Oxford or Swindon areas, no arenaceous horizons are developed. The ammonite faunas show great similarity with those of Kimmeridgian age farther south. The presence of commonly occurring specimens of the genus Subdichotomoceras in the autissiodorensis Zone is about the only distinguishing feature of these Yorkshire faunas. This genus has not, with any certainty, been recorded farther south in Britain. There is still a great deal to be learned about the Kimmeridge Clay of Yorkshire, but the nature of the ground suggests that surface exposures alone will not provide all the answers ; for this, a number of large diameter cored boreholes would be needed. ACKNOWLEDGMENTS I should like to record my gratitude to all who have contributed, in one way or another, to this work. In particular, I wish to thank Dr. J. H. Callomon for information on the Yorkshire exposures and many valuable discussions; the Department of Geology of the University of Hull for the loan of the Callomon and Donovan Collection; and Mr. J. A. Crossley, of Crossley Building Products Ltd., for permission to collect from the Golden Hill Pit. For donation of ammonites I thank Dr. P. Kaye and Mr . J. K. Wright. REFERENCES W. J. 1945. The Zones of the Upper Jurassic of Yorkshire. Proc. Yorks . geol. Soc ., 25, 339-58. - - -. 1947. The Geology of the Country around Weymouth, Swanagc, Corfe, and Lu1worth. Mem , geol. Sur v, U.K. 386pp. ARKELL,
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BAILEY, E. B. & J. WEIR. 1932. Submarine Faulting in Kimmeridgian Times in East Sutherland. Trans. R. Soc. Edinb., 57, 429-67. CALLOMON, J. H. & J. C. W. COPE. 1971. The Stratigraphy and Ammonite Succession of the Oxford and Kimmeridge Clays in the Warlingham Borehole. Bull. geol, Surv, Gr. sr., 36, 147-76. CASEY, R. 1967. The Position of the Middle Volgian in the English Jurassic. Proc. geol. Soc., 1640, 128-33. COPE, J. C. W. 1967. The Palaeontology and Stratigraphy of the Lower Part of the Upper Kimmeridge Clay of Dorset. Bull. Br. Mus. nat. Hist. (Geo!.), 15, 1-79. - - - - . 1968. Propectinatites, a New Lower Kimmeridgian Ammonite Genus. Palaeontology, 11, 16-18. ----.1974. The Upper Kimmeridgian Ammonite Faunas of the Wash Area Boreholes, and a Subzonal Scheme for the Lower Part of the Upper Kimmeridgian. Bull. geol, Surv, oi. Br., 47, 29-37. FALCON, N. L. & KENT, P. E. 1960. Geological Results of Petroleum Exploration in Britain 1945-57. Memoir No.2, Geol. Soc. Lond, SPATH, L. F. 1935. The Upper Jurassic Invertebrate Faunas of Cape Leslie, Milne Land, I. Oxfordian and Lower Kimmeridgian. Meddr Grenland, 99 (2) 1-82. ----.1936. The Upper Jurassic Invertebrate Faunas of Cape Leslie, Milne Land, II. Upper Kimmeridgian and Portlandian. Meddr Grenland, 99 (3), 1-180. ZIEGLER, B. 1962. Die Ammoniten-Gattung Aulacostephanus im Oberjura, (Taxionowie, Statigraphie, Biologic). Palaeontographica, A 119,1-172.