| Full text | |
| Author(s): |
Total Authors: 2
|
| Affiliation: | [1] Inst Nacl Pesquisas Espaciais INPE, OBT DSR, BR-12245970 Sao Jose Dos Campos - Brazil
[2] Univ Sao Paulo USP, Inst Geociencias, Programa Geol Sedimentar & Ambiental, BR-05508080 Sao Paulo - Brazil
Total Affiliations: 2
|
| Document type: | Journal article |
| Source: | Anais da Academia Brasileira de Ciências; v. 80, n. 3, p. 579-593, SEP 2008. |
| Web of Science Citations: | 9 |
| Abstract | |
Marajo 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 Marajo, even considering the dense forest cover. A well preserved paleodrainage network from the adjacency of the town of Breves (southwestern Marajo 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 Par River along fault lineaments. This would explain the disappearance of large, north to northeastward migrating channel systems in Southwestern Marajo Island, which were replaced by the much narrower, south to southeastward flowing modern channels. (AU) | |