57 E. Díaz-Martínez e I. Rábano (Eds.), 4 th European Meeting on the Palaeontology and Stratigraphy of Latin America Cuadernos del Museo Geominero, nº 8. Instituto Geológico y Minero de España, Madrid, 2007. ISBN 978-84-7840-707-1 © Instituto Geológico y Minero de España THE ALBIAN AMMONITE SUCCESSIONS OF THE SUBANDEAN ZONE OF ECUADOR L.G. Bulot 1 , E. Robert 2 , E. Jaillard 3 and W.J. Kennedy 4 1 FRE CNRS 6019, Université de Provence, Marseille, France. luc.bulot@up.univ-mrs.fr 2 Musée de Paléontologie, Université de Grenoble, France. 3 LGCA, Université de Grenoble, France. 4 Geological Collections, University Museum of Natural History, Oxford, UK. Keywords: Albian, ammonites, biostratigraphy, Ecuador, biogeography. INTRODUCTION The occurrence of Lower Cretaceous ammonites in Ecuador was first reported by Wasson and Sinclair (1927) and Tschopp (1953) on the basis of faunas collected from the Napo Formation and identified respectively by J.B. Reeside Jr., and M. Breistroffer.The aim of the present contribution is to update the Albian ammonite biostratigraphy of the lower part of the Napo Group on the basis of a revision of the material identified by Breistroffer in Tschopp (1953) and new collection made by one of us (EJ) during the course of a detailed field study of the of the ‘‘Oriente’’ of Ecuador (Fig. 1). Emphasis will be laid on cosmopolitan taxa that allow a correlation with the standard ammonite scales of Western Europe and the south-western USA. The remainder of the fauna, mainly Engonoceratids (Glottoceras), will only be briefly discussed by comparison with the stratigraphic description of the taxa in adjacent Andean basins (Peru and Colombia). GEOLOGIC AND STRATIGRAPHIC SETTING The studied area belongs to the Andean active margin that has experienced the subduction of the palaeo-Pacific oceanic plate in the Jurassic (Jaillard et al., 1990). During the Cretaceous Period, subduction went on beneath Peru but ceased beneath Ecuador, where various palaeogeographic areas can be distin- guished (Fig. 1). One of these is the East Ecuadorian (or ‘‘Oriente’’) Basin that underlies large areas of eastern Ecuador to Brazil and extends towards Columbia in the north and Peru to the south. It was characterised by low subsidence rates and marine sedimentation during most of the Cretaceous (Canfield et al., 1982). Two dif- ferent zones can be distinguished: (1) the Subandean Zone where Mesozoic outcrops allow field study of the Cretaceous successions presented herein; (2) the Amazonian Zone where marine Cretaceous rocks are only known through well data.