Ammonite faunas, OAE and the Pliensbachian–Toarcian boundary (Early Jurassic) in the Apennines

Bilotta, M., Venturi, F. & Sassaroli, S. 2010: Ammonite faunas, OAE and the Pliensbachian–Toarcian boundary (Early Jurassic) in the Apennines. Lethaia, Vol. 43, pp. 357–380. The critical Jurassic event known as Early Toarcian Oceanic Anoxic Event (OAE) has been the subject of several studies, but its palaeontological characterization is still problematic, and its dating is therefore debated. The rich ammonite faunas of the Mediterranean Tethys (Italy, Greece, Albania, North Africa, southern Spain, etc.) demonstrate that the OAE separates two very different assemblages, resulting from a strong post-OAE biological renewal. Faunas before the anoxic event include many taxa already present in late Pliensbachian (evolute Phylloceratida; Reynesocoeloceratinae, Protogrammoceratinae and Arieticeratinae), whereas after the anoxic event new forms radiated (Nodicoeloceratinae, Harpoceratinae and Hildoceratinae; afterwards also groups as Mercaticeratinae, Phymatoceratidae and Hammatoceratidae). As these assemblages show remarkable differences from their Northwest European equivalents, in the Apennine it is necessary to use a Mediterranean zonation, here formally established. The examined data suggest accurate boundaries for the OAE, which separates our first two Toarcian Zones, corresponding to Tenuicostatum and Serpentinum standard chronozones. Within this context, the Apennine assemblage placed immediately below the anoxic event is an endemic fauna with more than 15 ammonite genera, two of which (Secchianoceras and Petranoceras) are exclusive of the interval in question. Most abundant are Phylloceratidae (Phylloceras, Lavizzaroceras, Calaiceras and Harpophylloceras), Juraphyllitidae (Meneghiniceras) and Lytoceratidae (Lytoceras); Dactylioceratidae (Dactylioceras, Eodactylites and Secchianoceras) and Hildoceratidae are comparatively less numerous, but these latter show the largest taxonomic diversity (Fontanelliceras, Trinacrioceras, Protogrammoceras, Petranoceras, etc.). The description of this fauna improves the knowledge of a poorly understood interval immediately preceding the OAE, thus allowing better correlations in the Mediterranean area. □Ammonites, chronostratigraphy, Early Jurassic, OAE, Tethys.

[1]  A. Marok,et al.  Importance of the Mellala section (Traras Mountains, northwestern Algeria) for the correlation of the Pliensbachian-Toarcian boundary , 2009 .

[2]  L. C. Oliveira,et al.  AGES OF THE ONSET OF MARLY SEDIMENTATION AND OF THE BLACK SHALES IN THE TUSCAN BASIN (NORTHERN APENNINES, ITALY) , 2008 .

[3]  J. J. Gómez,et al.  Seawater temperature and carbon isotope variations in belemnites linked to mass extinction during the Toarcian (Early Jurassic) in Central and Northern Spain. Comparison with other European sections , 2008 .

[4]  K. Page.  The evolution and geography of Jurassic ammonoids , 2008 .

[5]  E. Mattioli,et al.  Marine microplankton and calcareous nannofossil palaeoecology of the Toarcian stratotype , 2007 .

[6]  M. L. Osete,et al.  Magnetostratigraphy of Early–Middle Toarcian expanded sections from the Iberian Range (central Spain) , 2007 .

[7]  H. Jenkyns,et al.  Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal) , 2007 .

[8]  A. Riccardi,et al.  Palaeomagnetic study of Lower Jurassic marine strata from the Neuquén Basin, Argentina: A new Jurassic apparent polar wander path for South America , 2006 .

[9]  E. Mattioli,et al.  The Early Toarcian anoxia, a synchronous event in the Western Tethys? An approach by quantitative biochronology (Unitary Associations), applied on calcareous nannofossils , 2006 .

[10]  P. Wignall,et al.  An eastern Tethyan (Tibetan) record of the Early Jurassic (Toarcian) mass extinction event , 2006 .

[11]  B. Nikitenko,et al.  Pliensbachian-Toarcian biotic turnover in north Siberia and the Arctic region , 2006 .

[12]  R. Twitchett.  The palaeoclimatology, palaeoecology and palaeoenvironmental analysis of mass extinction events , 2006 .

[13]  H. Jenkyns,et al.  Apparent sea-level change at times of extraordinary sediment supply: integrated facies analysis and chemostratigraphy of Early Toarcian Oceanic Anoxic Event, Peniche, Portugal , 2006 .

[14]  A. Hallam.  Facies and carbon isotope studies in southern Tibet suggest that the Toarcian extinction was diachronous , 2006 .

[15]  A. Coe,et al.  Astronomical pacing of methane release in the Early Jurassic period , 2005, Nature.

[16]  K. Miller,et al.  Toarcian oceanic anoxic event: An assessment of global causes using belemnite C isotope records , 2005 .

[17]  J. Dommergues,et al.  Les ammonites pliensbachiennes des nappes Lyciennes (Turquie méridionale). Description de faunes nouvelles, implications biostratigraphiques et paléobiogéographiques The Pliensbachian ammonites of the Lycian Allochton (southern Turkey). Description of new faunas, biostratigraphic and palaeobiogeogra , 2005 .

[18]  D. Rouby,et al.  Role of synkinematic ductile levels on the evolution of compressive zones – analogue modelling , 2004 .

[19]  K. Page.  A SEQUENCE OF BIOHORIZONS FOR THE SUBBOREAL PROVINCE LOWER TOARCIAN IN NORTHERN BRITAIN AND THEIR CORRELATION WITH A SUBMEDITERRANEAN STANDARD , 2004 .

[20]  F. Cecca,et al.  The two Early Toarcian (Early Jurassic) extinction events in ammonoids , 2004 .

[21]  S. Robles,et al.  Paleotemperature variations of Early Jurassic seawater recorded in geochemical trends of belemnites from the Basque-Cantabrian basin, northern Spain , 2004 .

[22]  K. Page.  The Lower Jurassic of Europe: its subdivision and correlation , 2003 .

[23]  Y. Rosenthal,et al.  Paleoceanographic changes of the Late Pliensbachian-Early Toarcian interval: a possible link to the genesis of an Oceanic Anoxic Event , 2003 .

[24]  A. Bartolini,et al.  A new scenario for the Domerian - Toarcian transition , 2003 .

[25]  A. Schmid-Röhl,et al.  Overgrowth on ammonite conchs: environmental implications for the Lower Toarcian Posidonia Shale , 2003 .

[26]  A. Vörös.  Victims of the Early Toarcian anoxic event: the radiation and extinction of Jurassic Koninckinidae (Brachiopoda) , 2002 .

[27]  F. Cecca,et al.  Biodiversity and biogeography of middle–late liassic ammonoids: implications for the early Toarcian mass extinction , 2002 .

[28]  F. Macchioni.  Myths and legends in the correlation between the Boreal and Tethyan Realms. Implications on the dating of the Early Toarcian mass extinctions and the Oceanic Anoxic Event , 2002 .

[29]  E. Mattioli,et al.  The response of marine phytoplankton and sedimentary organic matter to the early Toarcian (Lower Jurassic) oceanic anoxic event in northern England , 2002 .

[30]  C. E. Jones,et al.  Chemostratigraphy of the Jurassic System: applications, limitations and implications for palaeoceanography , 2002, Journal of the Geological Society.

[31]  Paul L. Smith,et al.  Dating the end-Triassic and Early Jurassic mass extinctions, correlative large igneous provinces, and isotopic events , 2002 .

[32]  M. Lomas,et al.  On the nature of methane gas-hydrate dissociation during the Toarcian and Aptian Oceanic anoxic events , 2002 .

[33]  L. Schwark,et al.  Palaeoenvironmental reconstruction of Lower Toarcian epicontinental black shales (Posidonia Shale, SW Germany): global versus regional control , 2002 .

[34]  J. Guex,et al.  Evolutionary Rates of Jurassic Ammonites in Relation to Sea-level Fluctuations , 2001 .

[35]  J. Guex,et al.  Découverte d'une importante lacune stratigraphique à la limite Domérien-Toarcien : implications paléo-océanographiques , 2001 .

[36]  M. Ettaki,et al.  Mise en evidence de la limite Pliensbachien-Toarcien par les ammonites, les foraminiferes et l'interaction tectono-eustatique dans la region de Todrha-Dades (Haut-Atlas central, Maroc) , 2000 .

[37]  A. Riccardi,et al.  The Neuquén composite section: magnetostratigraphy and biostratigraphy of the marine lower Jurassic from the Neuquén basin (Argentina) , 2000 .

[38]  Paul L. Smith,et al.  Synchrony between Early Jurassic extinction, oceanic anoxic event, and the Karoo-Ferrar flood basalt volcanism , 2000 .

[39]  C. Bjerrum,et al.  Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event , 2000, Nature.

[40]  D. Donovan,et al.  Strontium isotope profile of the early Toarcian (Jurassic) oceanic anoxic event, the duration of ammonite biozones, and belemnite palaeotemperatures , 2000 .

[41]  N. Perilli.  Calibration of early–middle Toarcian nannofossil events based on high-resolution ammonite biostratigraphy in two expanded sections from the Iberian Range (East Spain) , 2000 .

[42]  P. Harries,et al.  The early Toarcian (Early Jurassic) and the Cenomanian–Turonian (Late Cretaceous) mass extinctions: similarities and contrasts , 1999 .

[43]  J. Riding,et al.  Relationships between the early Toarcian anoxic event and organic-walled phytoplankton in central Italy , 1999 .

[44]  H. Jenkyns,et al.  Lower Jurassic epicontinental carbonates and mudstones from England and Wales: chemostratigraphic signals and the early Toarcian anoxic event , 1997 .

[45]  J. Vera,et al.  The Early Toarcian Anoxic Event in the Westernmost Tethys (Subbetic): Paleogeographic and Paleobiogeographic Significance , 1996, The Journal of Geology.

[46]  G. Parisi,et al.  Stratigraphy and geochemical anomalies of the early Toarcian oxygen-poor interval in the Umbria-Marche Apennines (Italy) , 1996 .

[47]  S. Elmi,et al.  L'étage Toarcien de l'Europe et de la Téthys; Divisions et corrélations , 1994 .

[48]  H. Jenkyns,et al.  An organic geochemical profile of the Toarcian anoxic event in northern Italy , 1994 .

[49]  M. K. Howarth.  The Ammonite Family Hildoceratidae in the Lower Jurassic of Britain , 1991, Monographs of the Palaeontographical Society.

[50]  H. Jenkyns,et al.  Jurassic Manganese Carbonates of Central Europe and the Early Toarcian Anoxic Event , 1991, The Journal of Geology.

[51]  H. Jenkyns.  The early Toarcian (Jurassic) anoxic event; stratigraphic, sedimentary and geochemical evidence , 1988 .

[52]  A. Hallam,et al.  Radiations and extinctions in relation to environmental change in the marine Lower Jurassic of northwest Europe , 1987, Paleobiology.

[53]  A. Hallam,et al.  The Pliensbachian and Tithonian extinction events , 1986, Nature.

[54]  H. Jenkyns.  The early Toarcian and Cenomanian-Turonian anoxic events in Europe: comparisons and contrasts , 1985 .

[55]  Felix Wiedenmayer.  Die Ammoniten der mediterranen Provinz im Pliensbachian und unteren Toarcian aufgrund neuer Untersuchungen im Generoso-Becken (Lombardische Alpen) , 1980 .

[56]  M. K. Howarth.  The stratigraphy and ammonite fauna of the upper Liassic Grey Shales of the Yorkshire coast , 1973 .

[57]  M. K. Howarth.  THE JET ROCK SERIES AND THE ALUM SHALE SERIES OF THE YORKSHIRE COAST , 1962 .

[58]  M. K. Howarth.  The Middle Lias of the Dorset coast , 1957, Quarterly Journal of the Geological Society of London.

[59]  M. K. Howarth.  DOMERIAN OF THE YORKSHIRE COAST , 1955 .