Seismic stratigraphy of a deep water basin in the Brazilian equatorial margin: the eastern portion of Potiguar Basin and Touros High

Abstract

The Brazilian Continental Margin (BEM) deep-water regions contain important geological features, although the area is poorly explored beyond the continental shelf-break. The main objective of this study is to seismically characterize syn- and post-rift sequences and certain seamounts that are part of the Fernando de Noronha Ridge (FNR) in deep-water basins and are off of the shore of northeastern Brazil. We used 2D post-stack high-resolution seismic sections to distinguish syn-rift, post-rift, and drift tectono-depositional phases. Three seismic horizons (R1 to R3) could represent, respectively, the following: an acoustic basement top, a rift top, and a highstand system tract (drift). The syn-rift stage is marked by discontinuous parallel reflectors with low amplitude and low frequency, which are offset by normal faults in half-grabens. The post-rift and drift stages are characterized by continuous parallel reflectors with low to high amplitude and frequency. Chaotic seismic reflections within the seamounts indicate their volcanic origins. Volcanic intrusions affected syn-rift, post-rift, and drift sequences and partially confine the deep-water basin deposition. The magmatic event occurred once the preexistent material and the sediment deposited after the seamount rises were partially confined by the continental slope and the seamounts. Seismic stratigraphy interpretation and its correlation with volcanic activities indicate a relative chronological control relating the emplacement of the seamounts to the Early Eocene to Late Miocene. Volcanic episodes seem to have created volcanoclastic deposits marked by a disorganized/chaotic seismic pattern with few continuous reflectors, indicating interbedded magma flows with sedimentary material. This paper provides an initial observation regarding the deep-water basin deposits on syn- and post-rift stages in the NE portion of the BEM.