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Pré-Publication, Document De Travail Année : 2005

Sedimentary record of terminal Cretaceous accretions in Ecuador: the Yunguilla Group in the Cuenca area

Résumé

A reappraisal of the “Late Cretaceous Yunguilla Formation” of the Cuenca area made it possible to define four distinct formations, correlatable with those of southwestern Ecuador. A mid to late Campanian marine transgression (Jadán Fm) is overlain by quartz-rich conglomerates of fan-delta to turbiditic fan environment (Quimas Fm) of latest Campanian-earliest Maastrichtian age, which are interpreted as evidence of the accretion of a first oceanic terrane (San Juan). Disconformable, arkosic turbidites and cherts (Tabacay Fm) 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 (Saquisilí Fm) 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. This suggests that in Ecuador, accretion of oceanic terranes contributed to the build-up of the Andes through tectonic underplating of low-density material, and that the eastern areas did not behave as a flexural foreland basins during late Cretaceous-Paleogene times.

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Dates et versions

hal-00128997 , version 1 (05-02-2007)

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Etienne Jaillard, Peter Bengtson, Martha Ordoñez, Wilmer Vaca, Annie V. Dhondt, et al.. Sedimentary record of terminal Cretaceous accretions in Ecuador: the Yunguilla Group in the Cuenca area. 2005. ⟨hal-00128997⟩
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