Assessing the Internal Uppermost Crustal Structure of the Central Pyrenees by Gravity‐Constrained Cross Sections

Abstract

The integration of geophysical modeling to classical structural studies constitutes a powerful approach to inferring the Earth's crust architecture (e.g.,

Salt Distribution in the South Pyrenean Central Salient: Insights From Gravity Anomalies

“…The gravity data we have used in this investigation comes from a compilation of available terrestrial gravity data acquired over the last 30 years (Ayala et al., 2016; Ayala, Rey‐Moral, Rubio, et al, 2021 and references therein). Within the study area, the data set comprises 12,727 gravity measurements (Figure 3a) of which 3,048 measurements were acquired in the past few years and led to a significant increase of the gravity resolution of the SPCS, from c. 1 measurement per 2–3 km 2 to c. 1 measurement per less than 1 km 2 (Ayala, Rey‐Moral, Rubio, et al., 2021; Ayala, Rey‐Moral, Rubio Sánchez‐Aguililla, et al., 2021; Clariana et al., 2022; Santolaria et al., 2016, 2020; Soto et al., 2022). As described in the referred papers, all the measurements were taken with relative gravimeters (mainly Scintrex CG5 and Lacoste & Romberg, with an accuracy of 0.001 and 0.005 mGal respectively).…”

“…The structural architecture was revisited through gravity forward modeling, especially in those parts of the cross‐sections where seismic profiles do not successfully image the structure at depth, well data is not available, and surface geology preclude an unambiguous interpretation. Previous gravity forward models in this area include regional crustal‐scale models of the western (Casas et al., 1997) and eastern (Torné et al., 1989) sides of the SPCS and smaller‐scale models including the south‐western (Santolaria et al., 2016, 2020) and south‐eastern terminations (Torné, 1989) of the salient and the southern Axial Zone and the northern part of the salient (Clariana et al., 2022; Piña‐Varas et al., 2023; Soto et al., 2022). Regional works tackled the overall crustal structure and therefore the scale of work differs from ours.…”

“…(2022), and Soto et al. (2022). Main structural units are limited by dotted/dashed red lines and labeled.…”

“…This along‐strike asymmetry is overprinted by several lower wavelength anomalies as described below. The Cotiella‐Bóixols Thrust Sheet shows a 40 km‐long and 22 km‐wide minimum (−18 mGal, Figure 4c, labeled CB2, Ayala, Rey‐Moral, Rubio, et al., 2021; Ayala, Rey‐Moral, Rubio Sánchez‐Aguililla, et al., 2021; Clariana et al., 2022; Soto et al., 2022). This minimum does not have a direct correlation with cropping out rocks but is likely related to low density rocks in the subsurface.…”

“…Observed residual Bouguer anomalies range from −34 to 14 mGal (Figure 4c). The gravity signal in the Axial Zone is characterized by a dominant gravity maximum with relative minima coinciding with the outcrop of Late Paleozoic granitoids or with buried granitoids and gneiss (Ayala, Rey‐Moral, Rubio, et al., 2021; Ayala, Rey‐Moral, Rubio Sánchez‐Aguililla, et al., 2021; Clariana et al., 2022; Soto et al., 2022). This large‐scale regional maximum can be associated with the usually higher density of Paleozoic rocks in the NE Iberian setting (Izquierdo‐Llavall et al., 2019; Pueyo et al., 2016; Toro et al., 2021) and the antiformal stack of the Axial Zone.…”