Journal of the Geological Society The Peterborough Member (Callovian, Middle Jurassic) of the Oxford Clay Formation at Peterborough, UK J. D. HUDSON and D. M. MARTILL Journal of the Geological Society 1994; v. 151; p. 113-124 doi:10.1144/gsjgs.151.1.0113 Email alerting click here to receive free email alerts when new articles cite this article service Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Journal of the Geological Society or the Lyell Collection Notes Downloaded by University of Portsmouth on 9 August 2010 © 1994 Geological Society of London Journal ofthe Geological Society, London, Vol. 151, 1994, pp. 113-124, 7 figs, 2 tables. Printed in Northern Ireland The Peterborough Member (Callovian, Middle Jurassic) of the Oxford Clay Formation at Peterborough, UK J. D. HUDSON & D. M. MARTILL Department of Geology, University of Leicester, Leicester LE1 7RH, UK Abstract: King’s Dykebrick pit, Whittlesey, near Peterborough, Cambridgeshire, provides a con- tinuous section through the Peterborough Member (formerly known as the Lower Oxford Clay)of the Oxford Clay Formation, and is here described as its type section. It also shows parts of the underlying Kellaways Formation and of the overlying Stewartby Member of the Oxford Clay Formation. Other sections in the Peterborough district are discussed and related to the type section. The Peterborough Member is developed throughout southern England and aspects of its stratigraphy, palaeogeography and burial history are briefly reviewed. The lower part of the Oxford Clay from around Company’s pit at King’s Dyke, near Whittlesey (national Peterborough, Cambridgeshire, was the source of raw grid reference [TL 248 9671) (Figs 1 & 2). This pit is worked material for the first modern bricks manufactured in Britain by shale planer so the face is steep, and not as convenient a century ago, the village of Fletton giving its name to a for collecting as in some of theother pits. It is more process that revolutionized the industry. The exposures in amenable to measurement, however, and the pit is likely to the extensive brick-pits have made the Oxford Clay a classic have an extended life; part of the face should be conservable subject for stratigraphicaland palaeontological research. when working eventually ceases. Theupper part of the Two outstanding feats of collecting will always be associated Kellaways Formationand the lower part of the Peter- with Peterborough: the assembly of the largest collection of borough Member, up to Bed 13 (of Callomon 1968; Fig. 3 marine reptiles ever made, by the Leeds brothers in the late herein), is exposed in drainage pits in the floor of the pit. nineteenth and early twentieth centuries (Andrews 1910-13; Bed 13 can be exposed by minor excavation at the base of Leeds 1956), and the statistical study of the evolution of the the main face, which exposes the PeterboroughMember ammonite Kosmocerus by Brinkmann (1929). Since the from Bed 14 upwards. The StewartbyMember (formerly advent of mechanical methods of working the clay, Middle Oxford Clay) forms the upper part of the face with a opportunities for fossil collecting have somewhat dimin- distinct lithological change to massive calcareous clays at its ished, but well-preserved skeletons of reptiles and fish are base; this is marked by prominent slips that terminate at this still being discovered at the rate of several per year, and the level (Fig. 2). ammonitescontinue to providea standardfor Middle Callovian bio- and chronostratigraphy (Callomon 1968; Page 1991). Martill & Hudson (1991) give a review of Oxford Graphic sections. Figure 3 is a log of the section based on Clay palaeontology, and Hudson & Martill (1991) discuss its examination of the beds in situ; key beds are indicated on palaeoenvironmental setting. the photograph (Fig. 2). Figure 4 includes a log of the Cox et al. (1993) have revised the nomenclature of the condensed lower beds. The equivalents of these beds have Oxford Clay Formation, defining the unittraditionally yieldedmost of the large vertebrate fossils recorded from known as the LowerOxford Clay as thePeterborough the Peterborough district (Martill 1985, 1986) and are char- Member, in accordance with current requirements of acterized by shell beds with abundant Gryphaeadilobotes stratigraphicalnomenclature (Whittaker et al. 1991). We Duff; we refer to them informally as the ‘Gryphaea and herein give adetailed description of itstype section at Reptile Beds’. A further informal marker bed is Bed 18, the King’s Dyke Pit, Whittlesey. The succession in the several ‘Dark Bed’, which shows up conspicuously in the lower part brick pits that are currently worked near Peterborough, or of the worked face, as its equivalents do in other brickpits that have been worked since the 195Os, is fairly constant, (e.g. Dogsthorpe, Horton et al. 1974, plate 8b). Two con- and generalized sections for the area are usually employed tiguous beds long recognized by their lithology and by (Callomon 1968). However, thereare variations in detail, ammonites, the Comptoni Bed and the Acutistriatum Bed especially in the lower beds, and some of the sections that (formerly Band), are important in correlation from Dorset have proved most fossiliferous in the past areno longer to Humberside. The ammonitezonation in Fig. 3 is after available. It is therefore important to record these sections, Callomon (1968) and Page (1991). The biofacies are from especially as collections from them have been used for Duffs (1975) analysis of the benthic faunas, supplemented geochemical studies (Williams 1988; Anderson et al., Kenig by our own observations. et al., this volume).We also discuss aspects of regional correlation,palaeogeography and palaeoenvironment that are relevant to the papers forming the thematic set included Bed numbers. A generalized section for the Peterborough in this volume. district was published by Callomon (1968), based in part on Brinkmann (1929), and has been the basis for all subsequent work. Duff (1978) compiled a section at Norman Cross Pit Type section [TL 186 9161, 8 km SW of Whittlesey, adding lithological The best and most continuous section currently available in and fauna1 detail to Callomon’s account. In Callomon’s thePeterborough Member is that at theLondon Brick section the bed numbering starts within the Cornbrash and 113 114 J. D. HUDSON & D. M. MARTILL f N I \\ Norman Cross 1 Fig. 1. (a) Sketch map of the Oxford Clay Formation outcrop in England, showing localities mentioned in the text. D, Dogsthorpe; 0, Orton; W, Whittlesey (all in the Peterborough district; see Fig. lb); S, Stewartby; B, Bletchley; C, Calvert; A, Ashton Keynes; CM, Christian Malford. (b) Map of the Peterborough brick manufacturing area, showing recently-active pits mentioned in the text (Dogsthorpe, King’s Dyke, Bunting’s Lane borrow pit, Orton, Norman Cross), the site of the Whittlesey borehole, and some disused pits (lined). includes the Kellaways Formation; the base of the Oxford Gryphaea. A section in the lower beds was exposed in a Clay is his Bed 4. In this account (Table 1) we start the bed temporary excavation in 1990, and the section shown in Fig. numbering at the base of the Peterborough Member and of 4 recorded. the Oxford Clay Formation, which we define above the last silty sand of the Kellaways Formation (Callomon 1968; Cox Orton. Orton Pit [TL 160 9401 exposes a similar section to et al. 1993). This is the level chosen by Brinkmann (1929) as Dogsthorpe; above Bed 19 the sequence is highly weathered level 0 in his centimetric measurement. We number addi- and devoid of calcareous fossils. It is worked by dragline tional beds in the basal part of the succession. Our bed and is currently the best pit for collecting, especially from numbers coincide with Callomon (1968) and Duff(1978) Bed 10. A distinctive feature is the occurrence of septarian from Bed 8 to the main part of Bed 14, the most important concretions in Bed 4, lower than that recorded by Martill part of the section for fossil collecting. The Duff and Callo- (1986). A section of the lower beds from a drainage sump is mon sections diverge above Bed 15; Duff employs a more included in Fig. 4. detailed subdivision up to and including the Acutistriatum Bed. Our numbering is similar butnot identical to his Norman Cross section. Duffs section does not extend above Bunting’s Lane. The temporary exposure at Bunting’s Lane the AcutistriatumBed and Callomon’s lacks detail;our [TL 200 9581, also known as Farcet Pit, was a borrow pit for numbering is new. part of the Peterborough Eastern by-pass thatexposed a complete section from the top of the Cornbrash, through the Other sections in the Peterborough district Kellaways Formation intothe lower part of the Peter- As noted by Callomon (1968) these can in general be readily borough Member. It afforded the best collecting in recent correlated with one another, and a common bed numbering years from the beds below Bed 10. A summary section is system applied. Difficulties arise principally in the included in Fig. 4. condensed lower beds. Norman Cross. The former brick pit at Norman Cross [TL Dogsthorpe. The brick pit atDogsthorpe [TF 210 0201, 1869161 was the site of the detailed collecting for Duffs which closed in 1990, was for many years a prolific source of (1975) palaeoecological studies. His section of the lower fossils, especially vertebrates. It was worked down to Bed 10 beds is shown in Fig. 4. andexposed fresh faces up to and including Bed 15. The generalPeterborough section given by Callomon (1968) Whittlesey core. Theauthors were presented with acore applies. The shell beds 11 and 13 contain abundant from a borehole sunk by the London Brick Company near PETERBOROUGH MEMBER, OXFORD CLAY FM 115 Discussion of the Peterborough sections Peterborough Member.