Three-dimensional shear velocity structure of the Mauléon and Arzacq Basins (Western Pyrenees)

Abstract

We present a 3-D shear wave velocity model of the Mauleon and Arzacq basins from the surface down to 10~km depth. This model is obtained by inverting phase velocity maps for periods from 2 to 9~s measured on coherent surface wavefronts extracted from ambient seismic noise by matched filtering. This new model, which is found in good agreement with local earthquake tomography, reveals the architecture of the Mauleon and Arzacq basins which were poorly imaged by conventional reflection seismic data. Combining these new tomographic images with surface and subsurface geological information allows us to trace major orogenic structures from the basement to the surface. In the basin, the models are successfully imaging first-order folds and thrusts at kilometric scale. The velocity structure within the basement and its geometrical relationship with the base of inverted rift basins supports a progressive northward exhumation of deep crustal and mantle rocks in the hanging wall of north-vergent Pyrenean thrusts. Our tomographic models image in 3-D orogen-perpendicular structures responsible for crustal segmentation as the Saison and Barlanes transfer zones. We propose that these steep structures consist in tear faults that accommodate the deepening of the Mauleon basin basement from west to east. To the west, this basement made of former hyper-extended rift domains (including mantle rocks) is anomalously sampled within the hanging-wall of north-directed orogenic thrusts, explaining its shallow attitude and its best preservation in comparison to the eastern segment of the study area. Eastward, the vertical shift of the basement makes that the former Mauleon basin hyper-extended rift basement remained in a footwall situation in respect of orogenic thrust and was underthrust. The comparison of the tomographic models obtained with surface wave tomography and local earthquake tomography shows that each approach has its own advantages and shortcomings but also that they are very complementary in nature, which would suggest to combine them in joint inversions to further improve passive imaging of the shallow crust and sedimentary basins.

Characterizing Natural Hydrogen Occurrences in the Paris Basin From Historical Drilling Records

“…In the Aquitaine Basin, the observed concentrations of H 2 can be linked to the geological context. Indeed, these wells are at the vicinity of a mantle body (peridotite) present at relatively shallow depths and are also located near major faults (e.g., major faults) facilitating fluid migration (Chevrot et al, 2018(Chevrot et al, , 2022Jammes et al, 2010;Lefeuvre et al, 2021Lefeuvre et al, , 2022Lehujeur et al, 2021;Tugend et al, 2014). Thus, within the scope of this study, we will specifically focus on investigating the origin of the H 2 anomalies in the wells of the Paris Basin.…”

Evolution of a low convergence collisional orogen: a review of Pyrenean orogenesis

“…3 and 4a) indicate the presence of a laterally restricted, dense body at shallow depth (11 km) below the Mauléon Basin (Fig. 4a; Wang et al, 2016;Chevrot et al, 2018;Lehujeur et al, 2021) corresponding to the Labourd positive Bouguer anomaly (Casas et al, 1997;Jammes et al, 2010;Wehr et al, 2018). Recent models propose that this is caused by mantle exhumed to shallow depths during Apto-Cenomanian hyper-extensional rifting and later passively integrated into the orogen above the northward subducting Iberian crust (Fig.…”

“…Recent models propose that this is caused by mantle exhumed to shallow depths during Apto-Cenomanian hyper-extensional rifting and later passively integrated into the orogen above the northward subducting Iberian crust (Fig. 4a; Wang et al, 2016;Lescoutre and Manatschal, 2020;Saspiturry et al, 2020;Lehujeur et al, 2021). This model is strongly debated, for example, by Teixell et al (2018) who instead argue that the tomographic and gravity data as well as the adjacent ECORS-Arzacq seismic reflection line (Fig.…”

“…Some models envisage exhumed mantle as a laterally continuous domain between symmetric or asymmetric hyperextended rift margins in a pure shear extensional model (e.g., Tugend et al, 2014aTugend et al, , 2014b; see Manatschal et al, 2021 for discussion). Given the highly segmented nature of the rift system (e.g., Jammes et al, 2009), mantle exhumation may alternatively have occurred in distinct rift segments (e.g., García-Senz et al, 2020;Lescoutre and Manatschal, 2020;Lehujeur et al, 2021) or in a patchwork of isolated transtensional or pull-apart basins if strike-slip played an important role along the Pyrenean domain (e.g., Lagabrielle and Bodinier, 2008;Canérot, 2017;Ford and Vergés, 2021;Asti et al, 2022).…”

Spatiotemporal Behavior of an Extremely Small Seismic Swarm in Pyrenean Foreland, France

“…The underlying idea was to quantitatively assess the imaging capabilities of a dense passive deployment, in a region with a clear scientific challenge, and where a profusion of available geological logs and seismic sections would provide strong independent constraints. Several studies have been so far dedicated to the exploitation of the data set collected or are still under way, among which the inversion of a 3-D shear velocity model based on the extraction of coherent surface wavefronts from ambient seismic noise (Lehujeur et al, 2021), a classical local ambient noise tomography (Boué et al, 2019), or a local earthquake tomography (Villaseñor et al, 2019;Lehujeur et al, 2021). In particular, the different tomographic models clearly outline a body characterized by very high velocities (see also Fig.…”