Seismostratigraphy of the inner shelf adjacent to Suape Bay, Northeastern Brazil

Abstract

Geotechnical and environmental studies widely use shallow geophysical imaging methods to indirectly acquire high-resolution subsurface data at a low cost for constructing three-dimensional models. Among these, seismic methods are especially valuable for investigating shallow submerged environments due to their capacity to produce detailed subsurface images. This study analyzes seismic facies patterns based on high-resolution shallow seismic profiles collected during a geotechnical investigation of the continental shelf offshore the Port of Suape, seeking to improve the understanding of the sedimentary and structural evolution of the transitional zone between the offshore and onshore regions of the Pernambuco Basin. The dataset comprises 14 multichannel 2D seismic sections, totaling 6.4 km of survey lines. Integrating sonographic data, borehole logs, sediment samples, and photographs enabled classifying three main types of seabed: (i) homogeneous mud seafloor; (ii) subaqueous dunes with gravel and sand; and (iii) irregular rocky substrate partially covered by sand. Interpretation of the seismic profiles identified five key reflections, including the present-day seabed and four major unconformities, And five seismic facies: (a) Facies I - unconsolidated sandy and muddy sediments (Quaternary); (b) Facies II - sandstones and shales of the Suape Formation (Lower-Middle Albian); (c) Facies III - basal deposits of the Cabo Formation (Barremian-Aptian); (d) Facies IV - carbonate mounds of the Estiva Formation (Cenomanian-Turonian); and (e) Facies V - crystalline basement (Ipojuca Magmatic Suite). Seismic and geotechnical data integrated allowed the reconstruction of stratigraphic layers associated with rift and post-rift phases of the basin. Additionally, a prominent positive seismic anomaly and normal faults trending NW-SE occurred at the basement top, suggesting extensional tectonic activity linked to the South Atlantic Rift.