Reconstructing the Iberian Salt‐Bearing Rifted Margin of the Southern Pyrenees: Insights From the Organyà Basin

Abstract

Reinterpretation of the Organyà Basin, based on new detailed field observations and subsurface data, emphasizes the key contribution of Upper Triassic evaporites in the tectono‐sedimentary evolution of the South‐Central Pyrenees. Results are integrated in a 65‐km long restored cross‐section through the Serres Marginals, Montsec and eastern Organyà salt‐related depocenters. The reconstructed part of the Jurassic–Cretaceous northern Iberian salt‐rich rifted margin shows a template characterized by inherited Permo‐Triassic basement normal faults and an initial salt thickness of 0.7 km to the south and 1.5 km to the north. The Organyà Basin is part of the South Pyrenean Diapiric Province, a large system of salt related depocenters and minibasins, that is limited to the north by the more than 120‐km long Senterada salt wall complex separating the supra‐salt and sub‐salt domains in the Southern Pyrenees. Three main stages of diapiric activity are recognized along the northern Iberian margin from Asturias to the Eastern Pyrenees: a Jurassic early salt mobilization; a latest Jurassic–middle Albian main diapiric evolution associated with rifting; and a Campanian–Miocene diapiric reactivation during basin inversion that produced salt welds and thrust welds and translated the salt province some 60 km to the south.

Translation, collision and vertical‐axis rotation in the Organyà and Montsec minibasins (South‐Central Pyrenees, Spain)

“…However, there are some differences in the general architecture and evolution of the basin presented here. Casini et al (2023) advocate for a faulted basement beneath the Organya basin that was active during the Late Jurassic and Early Cretaceous. Instead, we argue for a thick salt layer beneath both the Organya and Montsec mini-basins, with no syn-depositional basement faulting.…”

“…The structure is a 10°-50° south dipping monocline capped by an inlier of unconformable upper Albian-lower Cenomanian sandy limestones (Figures 3 and 4a). To the south, the strata of the Prada monocline thin over the pre-halokinetic Jurassic rocks at the bottom of the minibasin (Berástegui et al, 1990;Casini et al, 2023). The Santa Fe syncline has a plunge culmination to the east that appears as a fold closure in map view (Figure 3a).…”

“…Further to the east, north of Roca Narieda, the anticline axial surface consists of a vertical salt weld flanked by overhangs (Figure 5c). The weld contact connects with a vertical NE-SW trending fault, that is, Pont de l'Espia or Figols weld of Casini et al (2023), which preserves smears of Triassic red shales and gypsum and exhibits important extensional separation between map contacts (García-Senz, 2002). Salt remnants, thin and condensed sequences involved and along-strike variation of the geometry strongly suggest that the Bóixols anticline nucleated on a near surface diapir (e.g.…”

“…The thickness of the Cotiella, Aulet and Organya minibasins, located in the northern region, reaches a maximum of 5 km (e.g. Casini et al., 2023; Gannaway Dalton et al., 2022; García‐Senz & Muñoz, 2019a, 2019b; López‐Mir et al., 2014, 2016; Muñoz & García‐Senz, 2010; Saura et al., 2016). In contrast, the Montsec and Serres Marginals minibasins in the southern sector contain a relatively thinner pre‐orogenic Cretaceous succession, overlying thick syn‐orogenic units from the Upper Cretaceous to the Oligocene (Burrell et al., 2021; Cámara & Flinch, 2017; Espurt et al., 2019; Hudec et al., 2021; Figure 2).…”

“…Panoramic view of key outcrops. (a) View along the axis of the Canelles minibasin (Roca Narieda minibasin of Casini et al., 2023) showing a back‐stepped succession of carbonate platforms. Thick carbonate banks on the northern limb, represented by the Roca Narieda and Nargó Mbs, thin out to a few metres towards the southern limb where the Nargó carbonate bank culminates the succession.…”