AMMONITE FAUNAS, BIOSTRATIGRAPHY AND SEQUENCE STRATIGRAPHY OF THE CONIACIAN-SANTONIAN OF THE CORBIERES (NE PYRENEES) FAUNES D'AMMONITES, 8/0STRAT/GRAPH/E ET STRATIGRAPHIE SEQUENTIELLE DU CONIACIEN-SANTONIEN DES CORBIERES (NE DES PYRENEES) William James KENNEOY, Michel BILOTTE and Patrice MELCHIOR KENNEDY, W.J., BILOTIE, M. & MELCHIOR, P. (1995). - Ammonite faunas, biostra­ tigraphy and sequence stratigraphy of the Coniacian-Santonian of the Corbieres (NE Pyrenees). [Faunes d'ammonites, biostratigraphie et stratigraphie sequen­ tielle du Coniacien-Santonien des Corbieres (NE des Pyrenees)]. - Bull. Centres Rech. Explor.-Prod. Elf Aquitaine, 19, 2. 377-499, 38 fig., 30 pi.; Pau, December 26, 1995. - ISSN : 0396-2687. CODEN : BCREDP. Les faunes d'ammonites du Coniacien-Santonien des Corbieres sont revisees, et pres de 100 especes et sous-especes sont decrites. Les 4 zones d'associations classiques du Coniacien de I'Europe occidentale ont ete retrouvees, respectivement de la plus ancienne a la plus recente, les zones a Forresteria (Harleites) petroco­ riensis, Peroniceras (Peroniceras) tridorsatum, Gauthiericeras margae et Paratexa­ nites serratomarginatus. La base du Santonien est marquee par un important renouvellement faunique. Une seule zone d'association, a Placenticeras polyopsis, est reconnue; elle est divisee en 3 sous-zones, de bas en haut, les sous-zones a Nowakites carezi. Texanites ( Texanites) gallicus et Placenticeras paraplanum. ces especes ayant des extensions partielles concomittantes. Ni P. polyopsis, ni T. ( T.) gal/icusn'app araissent des la base du Santonien, dans les Corbieres; cette absence des placenticeratides comme des texanitides a la base du Santonien des Corbieres pourrait t!!tre liee a des conditions ecologiques defavorables. Les successions d'am­ monites etablies sont integrees aux sequences de depOt de l'intervalle de temps considere; les ll.ges absolus qui s' attachent a quelques especes fournissent la trame d'un premier cadre chronostratigraphique. William James Kennedy, Geological Collections, University Museum, Parks Road, Oxford, OX1 3PW. U.K.; Michel Bilotte, URA 1405 du CNRS, et Laboratoire de Geologie Sedimentaire et de Paleontologie, Universite Paui-Sabatier, To ulouse Ill, 39, a/lees Jules-Guesde, F-31062 To ulouse cEoEX; Patrice Melchior, Roquetaillade, F-11300 Limoux. -September 4, 1995. Mots-clefs : Monographie, Faune ammonite, Biostratigraphie. Coniacien, Santonien, Ammonoidea, Stratigraphie sequentielle, Aude, Corbieres. ABSTRACT and Placenticeras paraplanum. These species have partially over­ lapping ranges. Neither P. polyopsis nor T. (T.) gallicus range to the base of the Santonian in the Corbieres; placenticeratids and The Coniacian-Santonian ammonite faunas of the Corbieres are texanitids are absent from the lowest part of the stage there, pre­ revised, and nearly 100 species/subspecies described. The Conia­ sumably as a result of ecological exclusion. The ammonite succes­ cian can be subdivided into four assemblage zones. as elsewhere sion is integrated with the sequence stratigraphy of the interval. Forresteria (Harleites) in Western Europe, with successive zones of and provides a basis for assigning numerical ages to parts of the petrocoriensis, Peroniceras (Peroniceras) tridorsatum, Gaulhierice­ sequence. ras margae and Paratexanites serratomarginatus. The base of the Santonian is a level of marked faunal turnover. A single Assemblage Key words : Monographs, Ammonoids, Biostratigraphy, Coniacian, Zone of Placenticeras polyopsis is recognized, divided into Assem­ Santonian, Ammonoidea, Sequence stratigraphy, Aude, Cor­ blage Sub zones of Nowakites carezi, Texanites ( Texanites) gallicus, bieres. 0396-2687/95/0019-0377 $ 24.60 © 1995 elf aquitaine production, F-64018 Pau 378 W.J KENNEDY. M BILOTTE AND P MELCHIOR BCREDP 19 (1995) search through existing collections confirms this view, and CONTEN TS - TABLE DES MATII�RE5 shows the Santonian of the region to yield the most diverse fauna yet recognized in Western Europe, while the Conia­ INTRODUCTION ............................................................................ 378 cian yields four successive zonal assemblages that confirm 1. - REGIONAL GEOLOGY - G�OLOGIE R�GIONALE........ 378 the succession inferred by KENNEDY (1984a, b) elsewhere in France. Revision of these faunas show the Corbieres to be 1 .1. Previous work - Tr avaux anterieurs .. ...... .............. .... 378 a key region for our understanding of Coniacian-Santonian 1.2. Lithostratigraphy - Lithostratigraphie ....................... 378 ammonite stratigraphy; this stratigraphy can be integrated la - Les 1.2.1. The Gres de Sals (B,Lom, 1985) with the series of third order sedimentary sequences recent­ Gres de la Sals (81LOTTE, 1985)..................... 380 ly identified by BILOTTE ( 1992, 1993), while certain marker 1.2.2. The Calcaires de Montferrand (JAcos, 1938) species can be assigned chronostratigraphic ages on the - Les Ca/caires de Montferrand (JAcoa, basis of their occurrence the United States Western 1938) .. 380 in Interior, where they are associated with well-dated bento­ 1.2.3. The Formation de Bugarach (BILOTTE, 1985) nites (0BRADOVICH, 1993; GRADSTEIN et a/., 1994). - La Formation de Bugarach (81LOTTE, 1985) 380 1.2.4. The Lower Terrigenous complex - Le complexe terrigene inferieur.......................... 380 1.2.5. The Marnes Bleues de Sougraigne (ToucAs, 1879) - Les Mames Bleues de Sougraigne 1. - REGION AL GEOLOGY (TOUCAS, 1879).................................................. 381 1.2.6. The Montagne des Cornes sequence - La serie de la Montagne des Comes (ROLLAND 1.1. Du RoouAND, 184 1) ......... ................................. 381 PREVIOUS WORK 2. - 810- AND CHRONOSTRATIGRAPHIC RESULTS R�SUTATS 810 ET CHRONOSTRATIGRAPHIQUES ........ 381 De GRossouvRE ( 1901) provided a review of early work . 2.1. Coniacian - Le Coniacien ......................................... 383 on the Cretaceous of the Corbieres (D' ARCHIAC , 1859; Tou­ 2.2. Santonian - Le Santonien .............. .......................... 383 CAS, 1879; RoussEL, 1893; ... ), and gave the first coherent 2.3. Chronostratigraphy - Chronostratigraphie ............... 386 synthesis of the stratigraphy and faunas of the region. He particularly drew attention to the significance of two groups : 3. - DEPOSITIONAL SEQUENCES - LES SEQUENCES DE ammonites and rudists (of which the former are revised D�POT .................. .................................. ... ..... 386 below), noting that the former showed affinities with those 3.1. The Bugarach sequence : Coniacian-Lower Santo­ of Aquitaine, Provence, the Austrian Alps, Westphalia and nian - La sequence de Bugarach : Coniacien-San- tonien inferieur........................ .......................... 386 Bohemia, proposing that, should the Coniacian and Santo­ nian be united into a single stage, the term Corbierien be 3.2. The Montagne des Cornes sequence : Santonian used. pro parte - La sequence de la Montagne des Comes: Santonien pro parte .................................. .. 386 The next significant contributions on the Coniacian and 4. - LOCATION 03 bpau19-2F SECTIONS- SITUATION DES Santonian of the Corbieres came with the work of SIONESSE (1937, 1956), COUPES ........................................ .. _ . ..................... 387 who provided meticulous details of faunal occurrences, and BA SE (1939) who described ammonites 5. - CONVENTIONS - CONVENTIONS .................................. .. 388 S collected by SIONESSE, complementing the work of de GRos­ 6. - SYSTEMATIC PALAEONTOLOGY (W.J. KENNEOY) - souvRE (1894). This was amplified by BILOTIE OLLI N N PAL�ONTOLOGIE SYST�MATIQUE (WJ. 388 & C G O KENNEDY)......... (1983) who documented further additions to the ammonite 7. - REFERENCES ......... 434 fauna. 1.2. LITHOSTRATIGRAPHY IN TRODUCTION Lithostratigraphic units of Coniacian and Santonian age The Coniacian and Santonian stages were introduced by outcrop widely on the southern flank of the Massif de CoouAND in 1857, and have type areas around Cognac and Mouthoumet, notably in the synclines of Rennes-Jes-Bains Saintes respectively in the northern part of the Aquitaine and Bugarach-Soulatge (Fig. 1 ), where the Calcaires de Basin of SW France. Subsequent workers [e.g. ARNAUD, Montferrand and Marno-calcaires a Gauthiericeras are 1877, 1883; de GROSSOUVRE, 1901; SIORONIE-VIVIEN, 1972 (with referred to the Coniacian, the Marnes a Micraster, Calcaires extensive bibliography); KENNEDY (1984a: Coniacian, 1987: du Petit Lac, the terrigenous and bioconstructional Mon­ Santonian); PLATEL, 1989] have discussed certain inadequa­ tagne des Cornes sequence and their lateral equivalent, the cies of the type sections and type areas of the two stages, Marnes Bleues de Sougraigne, to the Santonian (Fig. 2). in particular their unsuitability as boundary stratotypes, and Following the work of SIONESSE ( 1956), we place the Turo­ the absence or great rarity of key biostratigraphic markers, nian-Coniacian boundary below the Calcaires de Montfer­ notably ammonites. rand, within the Gres de la Sals, a variable sequence that Already in 1901 de GRossouvRE realised this inadequacy overlies the hippuritid limestones of the Turonian and their and drew attention to the rich ammonite faunas of the lateral equivalents. Corbieres, a region much better suited for the characteri­ The Santonian-Campanian boundary cannot be placed zation of the Santonian stage. New collections (M. Bilotte with any precision; Upper Santonian marls being succeeded & P. Melchior)