Abstract
Marajó Island shows an abundance of paleochannels easily mapped in its eastern portion, where vegetation consists mostly of savannas. SRTM data make possible to recognize paleochannels also in western Marajó, even considering the dense forest cover. A well preserved paleodrainage network from the adjacency of the town of Breves (southwestern Marajó Island) was investigated in this work combining remote sensing and sedimentological studies. The palimpsest drainage system consists of a large meander connected to narrower tributaries. Sedimentological studies revealed mostly sharp-based, fining upward sands for the channelized features, and interbedded muds and sands for floodplain areas. The sedimentary structures and facies successions are in perfect agreement with deposition in channelized and floodplain environments, as suggested by remote sensing mapping. The present study shows that this paleodrainage was abandoned during Late Pleistocene, slightly earlier than the Holocene paleochannel systems from the east part of the island. Integration of previous studies with the data available herein supports a tectonic origin, related to the opening of the Pará River along fault lineaments. This would explain the disappearance of large, north to northeastward migrating channel systems in southwestern Marajó Island, which were replaced by the much narrower, south to southeastward flowing modern channels.
Highlights
The traditional view that the Amazon region remained environmentally stable during most of the Quaternary (e.g., Richards 1973, Heberle and Maslin 1999, Colinvaux et al 2000, Colinvaux and Oliveira 2001, Kastner and Goñi 2003) has been replaced in favor of a more dynamic environmental model, as a larger volume of information from different field areas becomes available
This study aims to provide sedimentological descriptions of a large paleochannel system recognized in southwestern Marajó Island (Fig. 1A)
This study helped to link, for the first time, geomorphologic features in southwestern Marajó Island to large channels associated to a palimpsest drainage system, with basis on sedimentological imprint provided by core descriptions
Summary
The traditional view that the Amazon region remained environmentally stable during most of the Quaternary (e.g., Richards 1973, Heberle and Maslin 1999, Colinvaux et al 2000, Colinvaux and Oliveira 2001, Kastner and Goñi 2003) has been replaced in favor of a more dynamic environmental model, as a larger volume of information from different field areas becomes available. Many modern Amazonian river courses show evidence for tectonic control (Bemerguy 1997, Silva 2005, Rossetti and Valeriano 2006, Almeida-Filho and Miranda 2007, Rossetti et al 2008). This large volume of works, among many others not cited helps to illustrate that the evolution of Quaternary Amazonian ecosystems is a complex issue. Different sedimentary successions are expected from one place to another
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
