Deciphering channel networks from aeromagnetic potential field data: the case of the North Sea Quaternary tunnel valleys

Abstract

Summary High-resolution magnetic data and potential field methods have been used to perform a detailed analysis of networks of late Quaternary subglacially-cut tunnel valleys (central Viking Graben, Norwegian sector of the North Sea). High-frequency, ribbon-like, sinuous, paired magnetic anomalies interpreted to be the signature of tunnel valleys are identified. Such magnetic anomalies have 1 to 8 nT amplitudes and reflect a magnetic susceptibility contrast between valley infills and the host sediments. Fractional vertical derivative and horizontal gradient transforms provide the best control on the accurately delineation of tunnel valleys by plotting automatically the extrema. The 2D forward modelling is a very effective approach to determinating the geometric parameters and magnetic susceptibility of the modeled valleys. It allows to determine the finite-width flat horizontal thin geometry as the most appropriate simple geometry to simulate the magnetic anomaly linked to a channel structure. The application of Euler deconvolution using complex algebra allows to substantiate the structural index (n = 1.5) for simple palaeovalley geometries and to determine fair valley depth estimates.

Large-scale, flat-lying mafic intrusions in the Baltican crust and their influence on basement deformation during the Caledonian orogeny

“…and second-order derivatives led to significant noise on the resulting map. As with the first-or second-order derivatives, the fractional vertical derivative delineates high-frequency magnetic anomalies and highlights linear features such as faults or dikes (Dentith and Mudge, 2014;Brahimi et al, 2020).…”

L'effet de la géométrie sur la précision dans l'estimation de la profondeur d'un réseau de type pipeline avec la méthode magnétique

“…A la différence de la définition eq 1., il s'agit non plus d'écrire une fonction complexe dépendant de deux variables réelles (𝑐𝑐 𝑥𝑥 , 𝑐𝑐 𝑧𝑧 ), mais d'une fonction complexe dépendant d'une variable complexe (𝑐𝑐 = 𝑐𝑐 𝑥𝑥 + 𝑖𝑖 𝑐𝑐 𝑧𝑧 ). La réécriture permet d'obtenir un lien simple entre la fonction complexe 𝐶𝐶𝐶𝐶𝐴𝐴 (0) (𝑐𝑐) et sa fonction dérivée 𝐶𝐶𝐶𝐶𝐴𝐴 (1) (𝑐𝑐) [9] :…”

Can Targeted Source Information Be Extracted From Superimposed Magnetic Anomalies?

“…Thus, igneous rocks exhibit a range of different magnetic parameters. Additionally, magnetic data are essential for studying the distributions and magnetic parameters of rocks that incorporate induced or remanent magnetizations, for example, metamorphic and sedimentary rocks and ores (Brahimi et al., 2019). Therefore, understanding the magnetic susceptibility, remanent magnetization, magnetization direction, and distribution is important for studying the spatial location, formation, and evolution of underground rocks (Miller et al., 2020).…”