Opening and tectonic and sedimentary evolution of the Gulf of Guayaquil: Neogene and Quaternary fore-arc basin of the south Ecuadorian Andes

The analysis of industrial seismic and well data of the Gulf of Guayaquil a llows us to constrain the structure of the Gulf of Guayaquir. The main open ing phase of the deepest South Ecuadorian Neogene and Quaternary fore-are b asin occurred during the Lower Pleistocene. It is located at the southern t ip of the Dolores-Guayaquil megashear zone, between WNW-ESE normal faults a nd north-south transpressional structures. The processes from which it orig inated are similar to those of a pull-apart basin. It developed between the Dolores-Guayaquil megashear to the east, and the oblique convergent Nazca- South America plate boundary to the west. During the Upper Pleistocene, the sedimentation rare decreases drastically in relation to both the glaciatio n-related sea level falls and a transpressional event. (C) Academie des sci ences / Elsevier, Paris.