Jaillard Etienne, Bengtson P., Ordonez M., Vaca W., Dhondt A., Suarez J., Toro J. (2008). Sedimentary record of terminal Cretaceous accretions in Ecuador : the Yunguilla Group in the Cuenca area. Journal of South American Earth Sciences, 25 (2), p. 133-144. ISSN 0895-9811.
Titre du document
Sedimentary record of terminal Cretaceous accretions in Ecuador : the Yunguilla Group in the Cuenca area
Jaillard Etienne, Bengtson P., Ordonez M., Vaca W., Dhondt A., Suarez J., Toro J.
Source
Journal of South American Earth Sciences, 2008,
25 (2), p. 133-144 ISSN 0895-9811
A reappraisal of the "Late Cretaceous Yunguilla Formation" of the Cuenca area enables the definition of four distinct formations, correlatable with those of southwestern Ecuador. A mid- to late-Campanian marine transgression (Jadan Formation) is overlain by quartz-rich conglomerates of fan-delta to turbiditic fan environment (Quimas Formation) of latest Campanian-earliest Maastrichtian age, which Lire interpreted as evidence of the accretion of a first oceanic terrane (San Juan). Disconformable, arkosic turbidites and cherts (Tabacay Formation) of early Maastrichtian age are thought to represent the erosion of the newly accreted oceanic terrane. A major unconformity of late Maastrichtian age, caused by the accretion of a second oceanic terrane (Guaranda), is followed by the deposition of quartz-rich micaceous shelf sandstones (Saquisili Formation) of Paleocene age. A third accretion event (late Paleocene) is recorded in coastal Ecuador. Each accretion event correlates with the uplift and erosion of the Eastern Cordillera and with a sedimentary hiatus in the eastern areas. In Ecuador, accretion of oceanic terranes contributed to the build up of the Andes through tectonic underplating of low-density material, and the eastern areas did not behave as flexural foreland basins during late Cretaceous-Paleogene times.
