Lowermost Amazon River: evidence of late
Quaternary sea-level fluctuations in a complex hydrodynamic system, Quaternary International, Volume 72,
Issue 1,
Helenice Vital and Karl Stattegger
Summary of
Points:
·
The article
claimed that sedimentological, geochemical,
and high-resolution seismic studies on the lowermost
·
Areas
of sediment transport and deposition on an older river bottom are delineated by
seismic reflectors and are related to inundation and incision caused by late Quaternary rising and falling of sea level.
·
Older
substrates have been identified as the Alter do Chão Formation (Cretaceous) and the Barreiras
Formation (Tertiary). The initial AMS-radiocarbon dates yielded late
Pleistocene to Holocene ages, and indicate a high sedimentation rate
(0.6 cm/yr) for the last 800 yr.
·
Three
stages in the late Quaternary evolution of the Amazon mouth system can be
distinguished: (i) relative sea-level fall, probably
related to the Last Glacial Maximum with channel incision; (ii) deposition and
consolidation of mud found near Afuá during relative
sea-level rise between late Pleistocene and middle Holocene, corresponding to
the "freshwater lake" or the evolution of large floodplain areas in Amazonia; and (iii) stable sea-level conditions since
6000 yr BP resulting in the modern pattern of deposition and erosion,
controlled by complex interactions of fluvial and oceanic processes.