The ammonite faunas of the Callovian-Oxfordian boundary interval in Europe and their relevance to the establishment of an Oxfordian GSSP 89 The ammonite faunas of the Callovian-Oxfordian boundary interval in Europe and their relevance to the establishment of an Oxfordian GSSP Kevin N. PAGE 1, Guillermo MELÉNDEZ 2 and John K. WRIGHT 3 1 School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK; e-mail: [email protected] 2 Paleontología, Dpto. Geología, Universidad de Zaragoza, Zaragoza 50009, Spain; e-mail: [email protected] 3 Department of Earth Sciences, Royal Holloway, University of London, Egham Hill, Egham, Surrey, TW20 0EX, UK; e-mail: [email protected] Key-words: ammonites, stratigraphy, palaeobiogeography, Jurassic, Callovian, Oxfordian, GSSP, Europe, Cardiocer a- tidae, Perisphinctoidea. ABSTRACT: The latest Callovian and Early Oxfordian are characterised by one of the highest levels of mixing of Boreal, Submediterranean and even Mediterranean faunas. In particular the massive expansion of Boreal Cardioceratidae from their original “home” in Arctic areas as far south as south-east France, brings them into contact with Mediterranean- style faunas rich in Phylloceratidae. This so-called “Boreal Spread” provides the framework within which high- resolution inter-bioprovincial correlations are possible and hence the context for a successful GSSP designation for the base of the Oxfordian Stage within Europe (and hence the beginning of the Upper Jurassic). Associated with the Cardioceratidae, especially in more Tethyan areas is a great variety of Perisphinctoidea, including Aspidoceratidae, Periphinctinae, Grossouvrinae and rarer Pachyceratidae as well as frequent Hecticoceratinae and rarer Phylloce- ratidae. As several of these persist beyond Europe they therefore provide tantalising indications that a truly global correlation of any GSSP established in Europe will ultimately be possible. The stratigraphical, taxonomic and palaeobiogeographical context and significance of the trans Callovian-Oxfordian boundary faunas within Europe is here reviewed and the faunas of the candidate GSSP at Redcliff Point, Weymouth, SW England are described, including the basal Oxfordian species Cardioceras (Pavloviceras ) redcliffense sp. nov. INTRODUCTION into contact with diverse Mediterranean-style faunas rich in Phylloceratidae (Pantethyan Realm The latest Callovian and Early Oxfordian or Superrealm). Not surprisingly, this intermixing represent one of the most dynamic intervals in the means that exceptionally detailed high-resolution history of Jurassic Ammonoidea and is characte- correlations are possible across the area, this rised by one of the highest levels of mixing of providing one of the best contexts for establishing Boreal, Submediterranean and even Mediterranean the Global Stratotype Section and Point for the base faunas. The key event is a massive expansion of the of any Jurassic Stage. range of Boreal Cardioceratidae from their original Associated with the Cardioceratidae in the home in Arctic Province areas (Panboreal Realm south is a great variety of Perisphinctoidea, inclu- or Superealm sensu Westermann 2000), across ding Aspidoceratidae, Periphinctinae, Grossouvri- Europe to as far south as SE France, bringing them nae and rarer Pachyceratidae as well as frequent 90 Volumina Jurassica, Volumen VII Hecticoceratinae, Phylloceratidae and Lytocera- ceratidae, with cadoceratids in the Lower and tidae. Most of these groups are commonest in Sub- Middle Callovian which evolve into Longaeviceras mediterranean and Mediterranean Province areas, in the early Upper Callovian and eventually but the Aspidoceratidae do persist well into the give rise to Cardioceras at the end of the terminal Pan-Boreal Realm and are locally common amongst Callovian , Lamberti Chronozone. The expansion the latest Callovian Subboreal faunas of England of Quenstedtoceras into Subboreal and Subme- and Scotland. Crucially, several groups of Peri- diterranean province areas – the Boreal Spread of sphinctoidea, including Peltoceratinae, do range Callomon (1985) – provides an excellent corre- beyond Europe and are known in East Pacific and lative event, now established as the base Indo-Pacific areas (Westermann 1992), therefore of the Lamberti Chronozone. Detailed records of providing tantalising indications that a truly global trans-boundary ammonite faunas from the Arctic correlation of any GSSP established in Europe will Province are few although there is no reason to ultimately be possible. suspect that the basic succession of Quenstedto- The current paper will review the stratigra- ceras to Cardioceras faunas differs in any phical, taxonomic and palaeobiogeographical con- significant way from that in adjacent Subboreal texts and significances of the trans-Callovian- areas, as described below. The local persistence Oxfordian boundary faunas within Europe, building of Longaeviceras into the Lower Oxfordian, on recent results from the candidate Oxfordian however, is noteworthy . GSSP near Redcliff Point, Weymouth, Dorset. There is some evidence, however, of ende- mic cardioceratid species in Boreal-Pacific areas (sensu Westermann 2000) of North America as BIOPROVINCIAL CONTEXT suggested by reviews in Westerman (1992, for instance pp. 29-92, 225 -272) . The East Pacific The marked north to south zonation of ammo- context of these faunas, however, may suggest nite faunas during the latest Callovian and Early that assignment to a different biogeographic pro- Oxfordian in Europe reflects a transition from vince might be more appropriate, perhaps even the relatively environmentally restricted and cooler a Northwest Pacific Province as is recognised at waters of the circum-polar Arctic Sea to the warm the end of the Jurassic and into the Lower Creta- margins of the Tethys Ocean. As would be expected, ceous ( cf . Page 1996). diversity increases steadily southwards and as a result a series of essentially east-west trending Boreal-Atlantic Realm: Subboreal Province bioprovinces are recognisable, as reviewed by Page (including England, Normandy, southern (1996, 2008 ). Although overlapping geographi- Germany, northern Poland, Russian platform) cal ranges facilitate some correlations between adjacent provinces, it is the sudden spread of the Subboreal Province Late Callovian to Early Cardioceratidae southwards from their Arctic home Oxfordian faunas are also dominated by Cardio- in the latest Callovian, that provides the context for ceratidae, but in addition include levels with correlation of the interval across Europe. The frequent Perisphinctoidea , especially Euaspido- character of each successive bioprovincial belt is ceras and Peltoceras (both Aspidoceratidae) and reviewed below. locally also Oppeliidae, including Hecticoceratinae. The Upper Callovian, Lamberti Subchronozone, Arctic or Boreal-Atlantic Realm: Arctic Province in particular the lamberti Biohorizon is particular (including Greenland,Spitzbergen, Alaska, diverse with a wide variety of Tethyan forms and western Canada, far eastern Russia, Scotland) also frequent Kosmoceras (K.) which is characte- ristic of the province , for instance in North York- A distinct Arctic Province for ammonoids shire (Wright 1968) . In the Lower Oxfordian, was already established in the Triassic and its although no clearly endemic Subboreal taxa are use in the Jurassic is reviewed by Page (1996). currently recognised (comparable for instance It is equivalent to the “inner Boreal ” Province of with Lower Callovian Proplanulitinae or Upper Callomon (1985), although often referred to as Oxfordian to Kimmeridgian Aulacostephanidae), simply a “Boreal Province ” by many authors. the Province maintains a clear Boreal character Callovian and Oxfordian Arctic Province faunas due to the dominance of Cardioceratidae. The pre- are virtually exclusively composed of Cardio- sence of frequent Tethyan forms, however, demon- The ammonite faunas of the Callovian-Oxfordian boundary interval in Europe and their relevance to the establishment of an Oxfordian GSSP 91 strates a classic “Subboreal ” character within an rare Phyllo- and Lytoceratidae. Representative Arctic to Mediterranean province spectrum of boundary sections are few, however, and most of the increasing Tethyan influence as has been described recorded fauna has been recovered from stratigra- by many authors ( e.g . Enay 1980; Page 1996, etc. ). phically condensed levels associated with a major A synthesis of typical Subboreal ammonite faunas regional non-sequence which typical omits most of in the UK is provided by Page (2004) and the can- the Middle and Upper Callovian and the Lower and didate GSSP near Redcliff Point in Dorset, SW basal Middle Oxfordian. Where typical faunas have England, as described in more detail below, been recorded, the Upper Callovian, including is characteristic. equivalents of the Lamberti Chronozone is chara- In Scotland (as reviewed by Page 2004) cterised by common Hecticoceratinae with varied the fauna is much less diverse and more Arctic Perisphinctoidea including Peltoceras , Alligati- in style. Latest Callovian faunas include typi- ceras and Poculisphinctes (Meléndez et al. 1982; cal Boreal Quenstedtoceras spp. with occasional Page et al. 2004). Remarkably, a few very rare Kosmoceras (K. ). With the exception of Eu- Kosmoceras (K.) are also known. Lower Oxfordian aspidoceras at one level, no other genera seem faunas are also dominated by Perisphinctoidea, to have been recorded.