Response of the Apodi-Mossoró estuary-incised valley system (NE Brazil) to sea-level fluctuations

  • Helenice Vital Conselho Nacional de Desenvolvimento Científico e Tecnológico; Departamento de Geologia
  • Samia F.Lima Furtado Petrobras
  • Moab Praxedes Gomes Universidade Federal do Rio Grande do Norte
Keywords: NE Brazilian shelf, Mossoró-Apodi Estuary, incised valley, sea-level changes, Seismostratigraphy

Abstract

This study focuses on the Quaternary sea level changes in the Apodi-Mossoró Estuary and adjacent shelf, Northeastern Brazil, based on the analysis of high-resolution seismic profiles, integrated with echosounder, SRTM and satellite image data. We use these data to develop a relative stratigraphy. An incised-valley extending from the Apodi-Mossoró Estuary onto the shelf dominates the investigated area. In very shallow waters (down to 10 m depth) the channel lies mainly in a NW-SE direction, changing to NE-SW in waters below10 m, in the form of a J-shaped valley. The southern flank of the shallow channel presents an abrupt morphology, probably determined by a residual scarp due to neotectonic reactivation of a pre-existing fault. This incised-valley can be correlated with a former river valley formed during the late Pleistocene fall in sea-level. The base-level change related to this drop in sea level can be regionally expressed on seismic lines as a laterally-continuous stratigraphic surface named Horizon I, interpreted as representing the sub-aerial exposure of the continental shelf. Many incised valleys were excavated on this exposed shelf, including that of the Apodi-Mossoró Estuary and its incised valley system. This incised valley has lain buried since the Holocene transgression. The Holocene sediments present sub-horizontal layers, or they have filled the incised valley with oblique features.

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Published
2010-01-01
How to Cite
Vital, H., Furtado, S., & Gomes, M. (2010). Response of the Apodi-Mossoró estuary-incised valley system (NE Brazil) to sea-level fluctuations . Brazilian Journal of Oceanography, 58(spe2), 13-24. https://doi.org/10.1590/S1679-87592010000600003
Section
naodefinida