The ''Celica-Lancones'' forearc Basin of southern Ecuador and northern Peru is located between the Paleozoic Amotape-Tahuin Massif to the west and NW and the continental volcanic arc to the east and SE. The study of nine sections and exhaustive sampling of the poorly fossiliferous, mainly clastic Cretaceous deposits of this Basin allowed us to define five distinct series, which display two depositional periods.The first period corresponds to the development of an Early (?) and Middle Albian carbonate shelf, interrupted during Late Albian times by the creation of a tectonically generated trough filled by turbidites of Late Albian-Coniacian age. Geological mapping indicates that this ''Celica-Lancones Basin s.s.'' includes distinct tectonic units, characterized by distinct early Late Cretaceous stratigraphic series and separated by major faults. These units can be grouped into two main paleogeographic domains. The southeastern one comprises mainly volcaniclastic deposits, whereas the northwestern domain exhibits quartz-rich deposits.Between Early Coniacian and Middle Campanian times, the ''Celica-Lancones Basin s.s.'' forerarc trough was deformed and eroded as a result of the Late Cretaceous ''Peruvian'' tectonic phase. The second period corresponds to the latest Cretaceous, during which a new forearc basin was created (Paita-Yunguilla Basin), which is much wider and strikes obliquely with respect to the Celica-Lancones Basin. The sediments of the Paita-Yunguilla Basin exhibit a comparable succession of Campanian-Maastrichtian age throughout the area and conceal the tectonic juxtaposition of the early Late Cretaceous tectonic units. The occurrence of thick Early(?) Maastrichtian coarse-grained conglomerates and breccias express a new significant tectonic event.La ''cuenca'' de ante-arco de Celica-Lancones del Suroeste de Ecuador y Noroeste del Peru esta ubicada entre el Macizo paleozoico de Amotape-Tahuin al Oeste y el arco volcanico continental al Este y SE. El estudio de una decena de secciones de campo y el muestreo de estos depositos cretacicos mayormente clasticos y poco fosilferos permite definir cinco series distintas, que evidencian dos perodos de depositacion.El primer perodo corresponde al desarrollo de una plataforma carbonatada de edad Albiana inferior (?) a medio, interrupido en el Albiano superior por la creacion de una cuenca turbidtica tectonicamente activa. El mapeo geologico demuestra que la ''Cuenca Celica-Lancones s.s.'' incluye unidades tectonicas distintas con diferentes series estratigraficas de edad Cretaceo superior temprano, separadas por fallas mayores. Las unidades pueden ser agrupadas en una provincia paleogeografica suroriental caracterizada por depositos mayormente volcanoclasticos, y un dominio noroccidental marcado por depositos clasticos ricos en cuarzo detrtico.Entre el Coniaciano inferior y el Campaniano medio, la cuenca de ''Celica-Lancones s.s.'' fue deformada y erosionado (''Fase Peruana'' del Cretaceo superior). El segundo perodo corresponde al Cretaceo terminal, durante el cual se formo una nueva cuenca de ante-arco (Cuenca Paita-Yunguilla) caracterizada por una serie Campano-Maastrichtiana homogenea en toda el area, que sella la yuxtaposicion tectonica de las unidades pre-santonianas. Mas luego, la ocurrencia de potentes conglomerados y brechas de grano grueso en el Maastrichtiano (?)temprano espresa un nuevo evento tectonico importante.