Reconstruction of geologic bodies in depth associated with a sedimentary basin using gravity and magnetic data

Abstract

A B S T R A C TWe present a comprehensive review of the most common gravity and magnetic interpretation methods to in depth retrieval of the geometry of geologic bodies associated with a sedimentary basin. We identify three types of bodies: 1) the sedimentary basement relief, 2) salt bodies and 3) mafic intrusions in a sedimentary section. In reconstructing basement topography through gravity and/or magnetic data we identify three groups of methods: the automatic, the spectral and the nonspectral methods. The reconstruction of salt bodies from gravity data usually uses interactive forward modelling but recently gravity inversion methods have been developed to interpret this kind of geologic environment. Finally, the problem of reconstructing intrusive bodies using magnetic and/or gravity data employs three strategies to interpret mafic or ultramafic intrusions in a sedimentary section: the automatic methods, interactive forward modelling and the inversion methods.

Estimating the nature and the horizontal and vertical positions of 3D magnetic sources using Euler deconvolution

“…This procedure is repeated over the whole data set in a moving-data window scheme. As pointed out by Barbosa and Silva (2011), this procedure has the disadvantage of computing a large number of inconsistent estimated solutions making it difficult to decide on the correct locations of the geologic sources. By assuming a null base level in equation 1, Silva and Barbosa (2003) deduce the analytical estimatorsx o ;ŷ o ; andẑ o (see equations 8-10 in Silva and Barbosa, 2003).…”

“…However, Manuscript received by the Editor 10 December 2012; revised manuscript received 9 June 2013; published online 4 October 2013. 1 this scheme leads to a large number of Euler solutions (Barbosa and Silva, 2011). This scenario is further complicated when the geometry of the source is unknown and when multiple sources with different geometries are present.…”

“…This procedure leads to a set of maps, each one displaying a broad cloud of Euler solutions, rendering nontrivial the interpretation of the locations of multiple geologic bodies. According to Barbosa and Silva (2011), the large number of estimated solutions by Euler deconvolution still remains an operational disadvantage of this method.…”

“…After the Reid et al (1990) extension, Euler deconvolution has gained enormous popularity as a semiautomated method to estimate the 3D position of magnetic sources. This popularity is because Euler deconvolution is a fast-processing method that requires no prior knowledge about the anomalous source magnetization, but just its homogeneity in intensity and direction (Barbosa and Silva, 2011).…”

Regularization parameter selection in the 3D gravity inversion of the basement relief using GCV: A parallel approach

“…Typically, most of the gravity-inversion methods developed to produce the depth-to-basement estimation approximate the sedimentary pack by a set of prisms with tops that coincide with the Earths's surface, and the thicknesses of the prisms represent the basement depths and are the parameters to be estimated. The study by Barbosa and Silva (2011) provides additional details about the methods used to recover the basement relief. Generally, these methods that discretize the basin into a set of prisms can be grouped into two categories.…”