bulletin de l'institut royal des sciences naturelles de belgique sciences de la terre, 66-supp.: 95-102, 1996 bulletin van het koninklijk belgisch instituut voor natuurwetenschappen aardwetenschappen, 66-supp.: 95-102, 1996 The Santonian Stage and substages by Marcos A. LAMOLDA & Jake M. HANCOCK, with contributions by Jackie A. Burnett, Christopher J. Collom, Walter K. Christensen, Annie V. Dhondt, Silvia Gardin, Kai-Uwe Gràfe, Jana Ion, Erle G. Kauffman, William James Kennedy, Ludmila F. Kopaevich, Gregorio Lopez, Tatsuro Matsumoto, Rory Mortimore, Isabella Premoli Silva, Francis Robaszynski, Jozef Salaj, Herbert Summesberger, Seichii Toshimitsu, Karl-Armin Tröger, Michael Wagreich, Christopher J. Wood, Elena A. Yazykova. PaboHaa Abstract rpynna CaHTOHCKoro npyca peKOMeHflyeT CHmaTb nepeoe nonBJieHue Cladoceramus undulatoplicatus (Roemer) KaK HHfleKC-bhfl KoHbHKO-CaHTOHa. PaöoHan The récognition of the Coniacian-Santonian boundary is easy with rpynna CaHTOHCKoro flpyca csHTaei, hto, Ha aaHHbiM MOMeHT, good corrélation of macro- and microfossil evidence. The Santonian cbopMa/ibHoe nperuioxeHne atih CTpaTOTuna rpaHHUbi He Working Group (SWG) recommends the lowest occurrence of Clado- MOXeT ÖblTb CtbOpMyjlHpOBaHO, T3K KaK ÖMOCTpaTMrpatJJHR emë ceramus as undulatoplicatus (Roemer) the marker for the Coniacian- He AOCTaTOHHO H3BeCTHa H flORXHa ÔblTb JiyHLUe Santonian boundary. As yet, the SWG cannot make a formai proposai MHTerpupoBaHa. npoBeneHHH 6o/iee noflpoÖHbix onbiTOB for a Boundary Stratotype Section, because the biostratigraphy must be 6bmn OTOöpaHbi 3 npeanoxeHMn CTpaTOTuna: Kapbep better known and integrated first. Three candidates for Boundary Olazagutia (Navarra, UcnaHMR), Seaford Head Stratotype Section, Olazagutia Quarry (Navarra, Spain), Seaford Head (Sussex, Ahmmh) m Ten Mile Creek (Dallas, TeKcac, (Sussex, England) and Ten Mile Creek (Dallas, Texas, USA) were CLUA). selected for further décision. To achieve a useful subdivision of the Pa3flejieHHe CaHTOHa Ha nofltnpycbi TpeôyeT JiyHinero Santonian into substages a better understanding of taxa ranges and nOHMMaHHR corrélation through different biogeographic realms is needed. Formai paCnpOCTpaHeHMSI TaKCOHOB m KoppejisuHM pa3Hbix 6noreorpad)HHecKMX paüOHOB. cpopManbHbie proposais for subdivision would be premature at present, but a three- fold division is favoured. npeflnoxceHMB no pa3flejieHHio apyca rbrhiotch npexcfleBpeMeHHbiMH; TeM He MeHee, pa3fleneHne Ha tph Key-words: Santonian. Upper Cretaceous, stratotypes, chronostrati- rioflbnpyca KaxeTcn npeflnoHTHTenbHbiM. graphy, biostratigraphy, ammonites, belemnites, crinoids, foramini- fera, inoceramids, nannofossils. KiiiOHeBbie cJiOBa: CaHTOHCKHÜ npyc, BepxHHÜ Men, cTpaTOTHnw, xpoHocTpaTHrpacfiHB, 6nocTpaTurpacbnçt, aMMOHMTbi, ôeneMHHTbi, Crinoida, 4>opaMHHM(t>epbi, MHOLtepaMbl, HaHOtbOCCHBHH. Résumé La reconnaissance de la limite Coniacien-Santonien se fait aisément grâce à une bonne corrélation sur base des marqueurs macro- et microfossiles. Historical Le Groupe de Travail du Santonien (SWG) a recommandé la pre¬ mière apparition de Cladoceramus undulatoplicatus (Roemer) comme The Santonian Stage was proposed by Coquand (1857), marqueur de la limite Coniacien-Santonien. Le SWG considère qu'une presumably town proposition formelle pour un stratotype de la limite ne peut pas encore named after the of Saintes in south-west être faite car la biostratigraphie est encore insuffisamment connue et France. One of the localities which Coquand mentioned doit être mieux intégrée. Trois propositions de stratotypes de la limite was Javrezac, a village on the north-west side of Cognac. ont été sélectionnées, la carrière Olazagutia (Navarre, Espagne), Sea¬ The boundary there was drawn on a hardground of glau- ford Head (Sussex, Angleterre) et Ten Mile Creek (Dallas, Texas, USA), pour des recherches plus approfondies. conitic, nodular limestone, with many "Exogyra', of the La subdivision du Santonien en sous-étages nécessite une meilleur Coniacian below, and soft micaceous chalk of the Santo¬ compréhension des extensions des taxa et une corrélation dans diffé¬ nian above. rentes régions biogéographiques. Des propositions formelles pour la subdivision de l'étage seraient encore prématurées, mais une division en trois sous-étages paraît préférable. At the First Symposium on Cretaceous Stage Boundaries (Birkelund et al., 1984) the consensus was that the first Mots-clefs: Santonien, Crétacé supérieur, stratotypes, chronostratigra- phie, biostratigraphie, ammonites, bélemnites, crinoides, foraminifè- appearance of Texanites (Texanites) and of Cladocera¬ res, inocéramidés, nannofossiles. mus undulatoplicatus (Roemer) are the two best boundary criteria. Texanites (Texanites) has been used over a wide area, CaHTOHCKHM Hpyc m noflbfipycbi: peKOMeHflaukiii PaSoneti although in classic régions of north-west Europe this rpynnw CaHTOHCKoro npyca. subgenus is far too rare to be a practical marker (Han¬ cock, 1991). Cladoceramus undulatoplicatus is wide- Pe3K»Me. spread, and owing to its characteristic form and sculpture PpaHHLta KoHbHKa m CaHTOHa nerKO ono3HaëTcn önaroflapn is easy to appearance cymecTByioLuefi Koppennu.nn HHfleKC-BHflOB MaKpo- h identify. The of Platyceramus MHKpOtJ)OCCHnHH. siccensis (Pervinquière) is well known in north Africa 96 Marcos A. LAMOLDA & Jake M. HANCOCK associated with Texanites, and it could be another possi¬ Discussion ble marker for the base of the Santonian. Ammonites In the Santonian Working Group report to the Second Symposium on Cretaceous Stage Boundaries (Brussels, Once it had been concluded that the species Texanites September 1995), other macro- and microfossils were texanus (Roemer) does not occur in the Aquitaine Basin, mentioned as possible indices for the Coniacian-Santo- nor in other European localities, (Birkelund et al, 1984) nian Boundary. pointed out the first appearance of the subgenus Texanites Thus, the lowest occurrence of the ammonite Placen- (Texanites) could still be a good marker of the Coniacian- ticeras polyopsis (Dujardin) is relatively close to lower Santonian boundary. Nevertheless, Texanites (Texanites) Texanites (Texanites). Similarly, the entry of the Sphe- is rare in many areas where other indices occur, only in noceramus pachti-cardissoides group is a possible mar¬ Zululand (South Africa), Madagascar and Texas is the ker for this boundary, associated with Texanites and subgenus common (reported by Kennedy, 1995). Cladoceramus undulatoplicatus. Further discussion on In the Anglo-Paris Basin, Texanitidae are rare, macrofossil criteria were reported by Kennedy (1995). although in a hard-ground level in the Craie de Villedieu, Published calcareous nannofossil events do not pre- France, Texanites gallicus Collignon occurs with Placen- cisely define the Coniacian-Santonian boundary, which ticeras polyopsis (Dujardin) and Inoceramus (Cladocer¬ Sissingh (1977) placed in CC 14 [above the first occur¬ amus) (Jarvis & Gale, 1984). In Sussex in S. England, rence (F.O.) of Micula staurophora (Gardet) Stradner]: Texanites has not been found, but Spinaptychus, an apty- e.g., the lowest occurrence of Reinhardtites anthophorus chus associated with Texanites, is recorded below and (Deflandre) Perch-Nielsen is unreliable (Wagreich, close to the Cladoceramus undulatoplicatus event (Bai- 1992), and recent studies (e.g., at Ten Mile Creek in ley et al., 1983, p. 34; see below in the inoceramid Dallas, Texas; J. A. Burnett, written comm.) show that chapter). the Coniacian-Santonian boundary actually lies above the Kennedy (1995) cited Germany as a région where F.O. of Reinhardtites anthophorus (i.e. in CC 15 of there are well documented co-occurrences of Texanites Sissingh, 1977). Nannofossil events which approximate and Cladoceramus undulatoplicatus (Roemer), particu- the boundary are (from stratigraphically old to young): larly the species Texanites (T.) pseudotexanus de Grous- F.O. of Lithastrinus grillii Stradner, last occurrence souvre (= Texanites texanus auct.). Seitz (1961) cited in (L.O.) of Quadrum gartneri Prins & Perch-Nielsen, the shaft Ewald Section the coexistence of T. texanum L.O. of Flabellites oblongus (Bukry) Crux (ail below (= T. (T.) pseudotexanus) and Inoceramus pachti (Ar- the boundary) and the L.O. of Lithastrinus septenarius khanguelsky) (fide Tröger, written comm.; see below Forchheimer above the boundary. Ail these events fall inoceramid chapter). within CC 15. Other nannofossil events, such as the L.O. In the Gosau Group, in Austria, Tröger & Summes- of Eprolithus floralis (Stradner) Strover, and F.O. of berger (1994), have reported that Texanites quinqueno- Micula concava (Stradner) Verbeek occur later or earlier dosus (Redtenbacher) co-occurs with Sphenoceramus than entries of Texanites and Cladoceramus undulatopli¬ cardissoides (Goldfuss) and Parapuzosia daubreei (de catus. Nevertheless, Flores et al. ( 1987) commented that Groussouvre). This assemblage is several metres below Micula concava and Lithastrinus grillii are present in the first occurrence of Cladoceramus undulatoplicatus, greater abundances in the Santonian than in the Conia- and above the Coniacian inoceramid Volviceramus invo- cian, and this may serve as a général guide, although lutus (J. de C. Sowerby). Such a sequence is well correl- nannofossil abundance is related to ecological and tapho- ated with Tröger's (1989) inoceramid biostratigraphy. nomical factors which are generally not cosmopolitan in Wagreich (1992) correlated lower Santonian localities in their extent. Austria (Gosau Valley