Evolution of the Amazon Basin in Ecuador with special reference to hinterland tectonics: data from zircon fission-track and heavy mineral analysis

摘要: The retro-arc Andean Amazon Basin (AAB), a foreland basin located east of the evolving Andes, has been an active sediment depocentre since the late Early Cretaceous (Aptian-Albian). Heavy mineral analysis of the proximal shallow marine and continental deposits in the Sub-Andean Zone reveals an overall trend from ultrastable zircon, tourmaline and rutile (ZTR) dominated assemblages, to more complex heavy-mineral suites with metamorphic and mafic volcanic signatures. This reflects successive derivation from shallow to deep crustal rocks and, subsequently, from accreted oceanic terranes during formation of the proto-Andes.In parallel with heavy mineral analysis, detrital zircons were dated using fission-track methodology. The measured lag times of the zircons range from 400 to 0 Ma. Approximately zero lag times generally represent fast cooling events in the source region, while long lag times are the …