Crustal configuration beneath the Santos and Campos Basins, southeastern Brazil: A refined Moho depth model based on gravity and seismic data in spherical coordinates

Abstract

The Santos and Campos Basin (SCB) represents not only a significant region for studying the passive margin geoscience in the South America but also holds promising potential for oil and gas exploration in the Brazilian seawaters. The investigation of Moho interface can provide valuable information for identifying the geological structure and characteristics of the SCB, enhance our understanding of the crust extensional mechanism, and thus promote significant advances in oil and gas prospecting. To further explore Moho configuration and provide reliable geological information for the SCB, we employ geologic stripping corrections, such as, the gravity effect of the seawater layer, variable density sediment in spherical coordinates, and low-pass filtering techniques to obtain the gravity anomalies of Moho interface. We apply fast nonlinear gravity inversion method in spherical coordinates to estimate a reliable Moho depth model, combining with Moho depth constraints derived from seismic imaging and 2D gravity-seismic modellings. Specifically, we conduct twice cross-validation methods to estimate the optimal regularization factor (μ), Moho reference depth (Mref), and crust-mantle density contrast (Δρ), and subsequently obtained Moho interface results. Also, various evaluations of the gravity Moho interface inversion results in evidence that the results are reliable. Subsequently, the crustal thickness, stretching factor β, thinning factor γ are derived from this Moho model to intensive investigate crustal configuration. Furthermore, based on these research findings, we discuss and analyze the crustal structure and attributes. The results reveal that the Moho depth in the study area is 38∼9 km, and the crustal thickness is 32∼4 km. Moreover, the Moho depth and crustal thickness gradually decrease from west to east overall. Various geophysical information identifies three distinct transitional zones: the purely-extended continental crust boundary (PECCB), the ‘Helmut’ anomaly tectonic lineament, and the continental-oceanic crust boundary (COB). The continental crust exhibits the structural feature of zoning along the NE direction and blocking in the NW direction, whereas the oceanic crust is characterized by blocking in the SN direction. Additionally, two V-shaped rifts are recognized in the study area. Ultimately, integrating these findings, we further reconstruct the PECCB and COB, redefine crustal attributes, and refine the attributes of the extended continental crust.