| Full text | |
| Author(s): |
Total Authors: 4
|
| Affiliation: | [1] Univ Sao Paulo, Inst Geociencias, BR-05508900 Sao Paulo - Brazil
[2] Inst Nacl Pesquisas Espaciais, Div Sensoriamento Remoto, BR-12245970 Sao Jose Dos Campos, SP - Brazil
[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil
Total Affiliations: 3
|
| Document type: | Journal article |
| Source: | Anais da Academia Brasileira de Ciências; v. 85, n. 1, p. 73-86, 2013-03-00. |
| Abstract | |
Studies suggest that the Marajó Island has experienced neotectonic activity during its latest evolution. However, there are no data demonstrating the presence of tectonic structures in its shallow subsurface. This work integrates vertical electric sounding, morphostructural lineaments, and geological data aiming to show fault control on the Late Pleistocene-Holocene sedimentation of this area. Resistivity values were related to mud (< 90 Ωm), clayey sand (90 and 200 Ωm), sand (200 and 500 Ωm), as well as Fe-bearing sand and laterite (> 500 Ωm). The latest values were related to the unconformity with lateritic paleosol at the top of the Barreiras Formation. Despite the values ≤ 500 Ωm of both the Barreiras Formation and the Late Pleistocene-Holocene unit, the latter was distinguished along four electric sections due to the presence of this unconformity, combined with the integration of available 14C, and luminescence ages of Quaternary sediments. The electric sections recorded several places with lateral interruptions of resistivity values within short distances, which were related to faults. The Miocene strata were vertically displaced by normal faults, giving rise to new accommodation space where Late Pleistocene-Holocene sediments were deposited. Fault reactivation was crucial to renew sedimentation in eastern Marajó Island during its latest evolutionary stage. (AU) | |