Basement‐Cover Relationships and Their Along‐Strike Changes in the Linking Zone (Iberian Range, Spain): A Combined Structural and Gravimetric Study

Abstract

Contractional deformation in the transition between the Iberian and Catalan Coastal Ranges (Linking Zone) generated both thin‐skinned structures detached in low‐strength Triassic units and basement‐involved structures. To evaluate their extent and relative contribution to the overall structure, we carried out a study combining structural geology and gravimetry. New gravity data (938 stations) and density determinations (827 samples) were acquired and combined with previous existing databases to obtain Bouguer anomaly and residual Bouguer anomaly maps of the study area. Seven serial and balanced cross sections were built, their depth geometries being constrained through the 2.5‐D gravity modeling and the 3‐D gravity inversion that we accomplished. The residual Bouguer anomaly map shows a good correlation between basement antiforms and gravity highs whereas negative anomalies mostly correspond to (i) Meso‐Cenozoic synclines and (ii) Neogene‐Quaternary basins. Cross sections depict a southern, thick‐skinned domain where extensional, basement faults inherited from Late Jurassic‐Early Cretaceous times were inverted during the Cenozoic. To the north, we interpret the existence of both Triassic‐detached and basement‐involved deformation domains. The two deformation styles are vertically overlapped in the southernmost part of the Catalan Coastal Ranges but relay both across and along strike in the Eastern Iberian Range. These basement and cover relationships and their along‐strike variations are analyzed in terms of the interplay between structural inheritance, its obliquity to the shortening direction, and the continuity and effectiveness of Triassic décollements in the study area.

Basement and cover architecture in the Central Pyrenees constrained by gravity data

“…The characterization of the rock density is fundamental in gravity surveys to constrain the modelling thus reducing the uncertainties in the modelled geometry (e. g. McCulloh 1965;Santolaria et al 2016;Izquierdo-Llavall et al 2019). The densities were measured from rock samples of the different lithologies represented in the two cross sections.…”

“…Considering the density contrast between host rocks and granites in the basement and between evaporites and other sedimentary rocks in the cover along the Central Pyrenees, in this work we use a workflow that combines the construction of two geological cross sections and their corresponding gravimetric models (see also Santolaria et al 2016Santolaria et al , 2020Izquierdo-Llavall et al 2019). The aim of this work was to investigate the basement and cover architecture in the Central Pyrenees and to constrain the geometry at depth and the volumetric distribution of the Triassic evaporites and the La Maladeta batholith.…”

Structural and Geophysical Characterization of the Western Termination of the South Pyrenean Triangle Zone

“…and lateral equivalents using gravity inversion. The density contrast between evaporitic units (Triassic and Eocene, [c]2.25 g/cm 3 ) on one side and nonevaporitic rocks (e.g., Oligocene detrital facies, [c]2.40 g/cm 3 ; Cretaceous limestones, [c]2.67 g/cm 3 ) or basement rocks ([c]2.75 g/cm 3 ) on the other, makes possible to use the gravimetric method (Calvín et al, 2018; Izquierdo‐Llavall et al, 2019; Pinto et al, 2005; Santolaria et al, 2016). In this work, the gravimetric data set has a dense coverage (more than 1 point per km 2 ) that allowed to model evaporite units and to detect lateral facies changes.…”

The enigmatic curvature of Central Iberia and its puzzling kinematics

“…Their lithological monotony, paucity of D. Pastor-Galán et al: The enigmatic curvature of Central Iberia fossils, and the intensity of deformation and metamorphism during Alpine orogeny make recognizing the original features of the different successions challenging (e.g., Martín-Algarra et al, 2019). Some faunal and detrital zircon studies suggest that the Paleozoic outcrops in the Betics may be similar to the most continental-ward realms of the Gondwanan platform (i.e., the Cantabrian Zone; e.g., Rodríguez-Cañero et al, 2018;Jabaloy-Sánchez et al, 2018). Following the latest plate reconstructions of the Mediterranean during Mesozoic-Cenozoic times, the Paleozoic units of the Betic-Rif chain may have been located proximal to the present-day position of the Balearic Islands (van Hinsbergen et al, 2020).…”

“…The structural geometry of the Central Iberian curve lacks such patterns. Paleomagnetism from the Iberian ranges indicate that the Cantabrian and West Asturian-Leonese zones do not follow the Central Iberian curve; instead they continue their WNW-ESE trend into the Mediterranean in what it is now the Betic chain (Rodríguez-Cañero et al, 2018;Jabaloy-Sánchez et al, 2018;van Hinsbergen et al, 2020). Structural trends in the Ossa-Morena and the South Portuguese zones do not show any change in along-strike structural trend which supports large-scale CW rotations (e.g., Pérez-Cáceres et al, 2015;Quesada et al, 2019), whereas existing paleomagnetic data from those zones (Leite Mendes et al, 2020) support a model of CCW rotation associated with the broader southern arm of the Cantabrian Orocline.…”