FOSSIL OCCURRENCES IN THE UPPER CENOMANIAN - LOWER TURONIAN AT GANUZA, NORTHERN SPAIN - AN APPROACH TO CENOMANIAN TURONIAN BOUNDARY CHRONOSTRATIGRAPHY/

An Upper Cenomanian to Lower Turonian section has been sampled in the vicinity of Ganuza, northern Spain. Ammonoids, inoceramids and microfo ssils including foraminifera and calcareous nannofossils have been stu died. We recognize three planktonic foraminiferal biozones: the Rotali pora cushmani, Whiteinella archaeocretacea and Helvetoglobotruncana he lvetica Zones. We also characterize the Eiffellithus turriseiffelii an d Quadrum gartneri Zones, based on nannofossil biostratigraphy. Macrof aunal occurrences are scarce but allow us to characterize the Metoicoc eras geslinianum and Mammites nodosoides Zones, and two inoceramid ass emblages. In the Rotalipora cushmani Zone the following sequence of bi ohorizons is recorded from bottom to top: (a) last occurrence (LO) of Corollithion Kennedyi; (b) LO of Rotalipora greenhornensis; (c) LO of Axopodorhabdus albianus; (d) first occurrence (FO) of Euomphaloceras s eptemseriatum, (e) LO of Lithraphidites acutus; (f) LO of Rotalipora c ushmani. In the Whiteinella archaeocretacea Zone the sequence of event s is as follows: Cg) FO of Calycoceras naviculare; (h) LO of Microstau rus chiastius; (i) FO of Quadrum intermedium; (j) FO of Helvetoglobotr uncana praehelvetica; (k) FOs of Kamerunoceras sp. and Mytiloides subm ytiloides; (1) FO of Mytiloides kossmati kossmati; (m) FO of Kamerunoc eras calvertense; (n) FO of Quadrum gartneri; to) FO of Mammites nodos oides; (p) FO of Mytiloides mytiloides. The top of this zone is marked by the FO of Helveroglobotruncana helvetica. A possible Cenomanian-Tu ronian (C/T) boundary can be drawn between FOs of Kamerunoceras sp. an d Mytiloides submytiloides and the FO of Mytiloides kossmati kossmati. Successive FOs of H. praehelvetica and Q. gartneri are also good prox ies for the C/T boundary. (C) 1997 Academic Press Limited.