Stratigraphy and evolution of the Cretaceous forearc Celica-Lancones basinof southwestern Ecuador

The "Celica-Lancones" forearc Basin of southern Ecuador and northern Peru i s located between the Paleozoic Amotape-Tahuin Massif to the west and NW an d the continental volcanic are to the east and SE, The study of nine sectio ns and exhaustive sampling of the poorly fossiliferous, mainly elastic Cret aceous deposits of this Basin allowed us to define five distinct series, wh ich 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 creatio n of a tectonically generated trough filled by turbidites of Late Albian-Co niacian age, Geological mapping indicates that this "Celica-Lancones Basin s.s." includes distinct tectonic units, characterized by distinct early Lat e Cretaceous stratigraphic series and separated by major faults. These unit s can be grouped into two main paleogeographic domains. The southeastern on e comprises mainly volcaniclastic deposits, whereas the northwestern domain exhibits quartz-rich deposits. Between Early Coniacian and Middle Campanian times, the "Celica-Lancones Ba sin s.s." forerarc trough was deformed and eroded as a result of the Late C retaceous "Peruvian" tectonic phase. The second period corresponds to the l atest Cretaceous, during which a new forearc basin was created (Paita-Yungu illa 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 a nd conceal the tectonic juxtaposition of the early Late Cretaceous tectonic units. The occurrence of thick Early(?) Maastrichtian coarse-grained congl omerates and breccias express a new significant tectonic event. (C) 1999 El sevier Science Ltd, All rights reserved.