Batizonjan - Callovian(Middle Jurassic)ammonite faunas of the Northwest Iberian Ranges: b iostratigraphy and palaeobiogeography J. THIERR’? and 5. WILDE** 0 157 «Géodynamique sédimentaire et Evolution géobiologique» * URA ~ii7NRSn eL Centre des Sejences de la Terre, Université de Boargogne, 6 Rd Gabrial 21100 DIJON (France) ** Jns¿ñrnJí¿r Gealogie, Ruhr-Universitñ¿ D-4630 BOCHUM, (RE4) XBSTRACT Thc Bathonian-Callovian carbonated sedimenis, sometimes sandy or silty and ctayish, of the Iberian ptatform in Ihe Sierras de la Demanda, Cameros ami Moncayo near Burgos, Logroño, Soria ami Zaragoza (North- west Iberian Ranges) yeld significant ammonite faunas for a precise bios- tratigraphic approach; these also allow sorne biogeographic remarks about Ihis region situated in platform environrnents almost off on the North Tethyan margin. During the Bathonian (Montenegro, Soria, Olvega and Ricla forma- tions) the faunas are dominated by the Perisphinctidae (Procerites, Siemi- radkia, Wagnericeraá; h’omeop/anulñes. Ch~ffatia —70 %)4 the other taxa are sorne Oppelidae (Oxycerites, Qecotraustes Prohecticoceras —20 %). Parkinso- niidae (Gonolkites bipistrenoceras —5 %) and Tulitidae íBullatimorphites —5 %). The various recognized species allow to conclude that the Lower Bathonian (Zigzag zone; Convergens and Yeovilensis subzones) is repre- sented as weIl as the Middle Bathonian (Progracilis and Subeontractus zones; Subeontractus and Morrisi subzones) and the Upper Bathonian (Retrocostaturn zone and subzone). It must be noted that Morphoceratidae of Lowermost Baihonian and Clydoniceratidae of Upperrnost Bathonian are missing. In Callovian, (Montenegro, Pozalmuro and Ricla formations) only Ihe lower pad of Ihis stage is dcli in ammonites. The Macroceplialus and Gracilis zones are weII distinguished witb prevalent Macrocephalitidae (Macrocephalites —45 %) and Perisphinctidae (Choifatia, Homeoplanulites, Indosphinctes, Grossouvria —40 %). The Tulitidae (Bullatimorphites), Reinee- keidae (Rehmannia) aud Oppeliidae (Chanasía) are very rare (15 %). 11w Middle, and overail, the Upper Callovian are less fossiliferous and uncom- Cuadernos dc Geología IMita N.” 14. 43—156. Moc] rld. [990. Ecli 1. LI ri ‘ersicl aci (orn pl utcnsc. 144 J Thíerry and 5 Wilde plete: howewer, the Anceps, Coronatum and Athleta zones are sometimes recognized with Hecticoceratinae (Hecticoceras, Rossiensisseras, Lunuloce- ras) and Perisphinctidae (Grossouvria, Indosphincees, Flabellisphinctes). One shall note the absence of Ihe Pacbyceratidae (Erymnoceras) and Peltocera- tidae. From the biogeographic point of view, we corroborate that this region takes place in the so-called- «Sub-Tethyan realm» where the boreal Callo- vian Kosmoceratidae and Cardioeeratidae are missing while in dic Hatho- fian, the faunas look like ah that of the other South-West European arcas- «Sub-Boreal realm» -as a consequence of historical faetors of distribution. Nevertheless. ecological factors play an important par in the geogra- phical distribution of the ammonites. The bathymetry appears as dic most important factor eonsidering the complete missing of Phyfloceratids and Lytoceratids boíh in Bathonian and Caflovian in comparison. for instanee, w¡th the Prebetic and Subbetic Ranges which are under ocean¡c influences in the «Tethyan realm». Localy, ammonites are also exciused from the very shallow facies while tbey are relatively more abundant in deeper facies; sandy or silty-clayish deposits respectively in South-West Demanda and North-West Moncayo seems to have no influence upon ammonite faunas in comparison with thai in dic more carbonated sedimenis. Key words: Biostratigraphy, Palaeobiogeography, Aminonites, Middle- Jurassic, Bathonian-Callovian. Iberic Ranges. RESUMEN En los Ibérides noroccidentales (Sierras de la Demanda, Cameros y Moncayo) los sedimentos referidos al Bathoniense-Calloviense se presen- tan generalmente como calizas micriticas más o menos detríticas y bio- clásticas. Se estudia aquí, con concurso de las faunas de ammonites, los aspectos dc la bioestratigrafia y dc la palcobiogeografia en cl sector Bur- gos-Logroño-Soria-Zaragoza. Durante el Bathoniense (Formaciones Montenegro, Neila, Olvega y Ricla) las faunas son dominadas por los Perisphinctidae (Proceriteg Siemi- radekia. Wagnericcras, Homeoplanulitc,; Choffatia —70 %) y los Oppelidae (Oxycerites; Occotraustes, Prohecticoceras —20 %t algunos Parkinsoniidae (Co- nolkitcs, Epístrenoceras) y Tulitidae (Bullatimorphites) completan esta fauna (10 %). Se puede reconocer el Bathoniensc inferior (zona de Zigzag; subzo- nas de Convergens y Veovilensis), el Batboniense medio (zonas de Progra- cihis y Suhcontractus; subzonas de Subcontractus y Morris) y el Batho- niense superior (zona y subzona de Rctrocostatum). Faltan totalmente las familias Morphoceratidae dc la base del Batboniense y Civdoniceratidae de la parte más superior de este piso. Bathonian-Ca¡lovian (Miádie Jurassic) ainrnon¡te faunas... 145 Solamente el Calloviense inferior es muy fosilífero (Formaciones de Montenegro, Pozalmuro y Ricla). Las zonas de Macrocephalus y Gracilis se caracterizan por la abundancia de los Macrocephalitidae (Macrocephalites —45 %) y Perisphinctidae (Choifaria, Homeoplanulites, Jndosphinctes, Gros- souvria —40 %). Los Tulitidae. (Bullatimorphites), Reineickeidae (Reliman- nia) y Oppelidae (Chanasia) no representan juntos, más del 15% de la fau- na ammonitica. El Calloviense medio y el Calloviense superior faltan en muchos perfiles; cuando existen son poco fosilíferos. La zona de Anceps, y a veces las zonas de Coronatum y Athela, revelan sobre todo Hecticocera- tinae (Hecticoceras, Rossiensiceras, Lun uloceras) y Perisphinctidae (Grossouv- ría, Indosphínczes, F¡abellísphínctes); los Pachyceratídae (Erymnoceras) y Pel- toceratidae no existen. Estos datos confirman la pertenencia de los Ibérides noroccidentales a la «Provincia subthethisiana». En el Calloviense faltan totalmente los Kostnoceratidae y Cardioceraitidae de las áreas boreales, mientras que en el Bathoniense la fauna se parece a la que se encuentra corrientemente en el suroeste de Europa. Los factores históricos desempeñan aquí un papel muy importante. Sin embargo, los factores ecológicos son responsables de la ausencia de los Phylloceratidac y Lytoceratidae cuya distribución está condicionada por la profundidad. Localmente, el factor batimétrico inter- viene también: los ammonites son mas abundantes y diversificados en las áreas profundas que en las plataformas superficiales. La composición del sedimento, más o menos carbonatado y más o menos bioclástico, arenoso y margoso, parece no influir sobre el porcentaje respectivo de las familias. Palabras claves: Bioestratigrafía. Paleobiogeografía, Ammonites, Jurá- sico Medio, Bathoniense-Calloviense, Cordillera Ibérica. INTRODUCTION The Northwestern arcas of the Iberian Ranges between Burgos, Logro- ño, Zaragoza aud Soria is built with the Sierras de la Demandalde los Cameros and the Sierras del Madero/del Moncayo. The general stratigra- phical and palacgeographical elements of thc Bathonian and Callovian stages hLve been studied by Mensink (1966) and Bulard (1972). Later, various authors gaye more precise details in sedimcntay facies about the carbonated rocks of these regions (Valladares. 1976; Benke, 1981; Mcnsink and Mertmann, 1984; Wilde. 1988). From the biostraíigrapbicai and pajaeobiogeograpbical points of view, the North-Wesí Iberian ranges are not so well known as the South-Eastem part of the «Rama Aragonesa» —South of Zaragoza— and the «Rama Castellana» —South of Teruel— (Marín andToulouse, 1972; BulardetaL, 1974; Sequciros, 1980. 1982 a,b, 1984; Sequciras and Cariou. 1984; Sequei- 146 J Thier¡y and 5 Wilde ros ci al?, 1984; Conze et al.. 1984; Sequciros and Melendez. 1979, 1987; Cariou u aL. 1987). The reccnt work in te North West Iberian Range of one of us (5. Wilde), dic determination of about 270 new collected ammonites and the revision of the faunas of Bulard’s collections preserved in Dijon (J. Thier- ry). allow us to give a more detailed biostratigraphical framework of this realin. Ihe transition area between dic North-West Iberian Range. The Zaragoza region near Ricla. Aguilon and Belchite. is included in dic study by literature comparisons. Some biostratigraphical and biogeographical remarks on ammonites can be stated and comparisons with other South- Wcst European regions can be made to replace Ibis Iberian area in the wídcr context of dic North Tethyan xwargin during thc Middle-]urassic. AMMONITE FAUNAS AND BIOSTRATTGRAPHY The Bathon¡an la West Madero. Madero and Northwest Moncayo regions, Middle aná Upper Bathonian is missing partly or entircly. In other arcas the stage is enough fossiliferous. The bathonian sequenee is separated from Ibe Bajo- cian by an important guide horizon with unconformities and ammonite cnrichmcnt leveis which indicate the Upper Bajocian. mostly Niortense, Garantiana and Parkinsoni zones or parts of this. TEe most fossiliferous facies is dic Montenegro Formation of the De- manda-Cameros regions, some ammonites are also found la the Neila Formation. In the Madero-Moncayo territory ammonites are tare in the Olvega, absent in thc Manubles and Soria Formations. Again they are aboundant in dic open marine Biela Formation south of Zaragoza. The main biostratigraphic subdivisions can be recognized. In dic LowcrBatho- alan, dic Zigzag zones is weB represented witb distinetive Parkinsoniidae (10 %) of thc Convergeas subzone-Parkinsonia (Gonolkites,l cf eimensk~ E (G.) cf neuffensis and E (G.) cf convergens.