The Naval diapir (southern Pyrenees): Geometry of a salt wall associated with thrusting at an oblique ramp

Abstract

The southern Pyrenees provide several examples of diapiric structures linked to migration of Triassic evaporites associated with the movement of thrust sheets. Among them, the Naval diapir, the westernmost diapiric body in the Sierras Marginales unit, is key to understanding the mechanisms controlling salt tectonics in this sector of the Pyrenees. In this paper, we use geological mapping, field data, cross-sections, seismic reflection profiles and detailed gravity data to characterize the geometry of the Naval diapir, a body of Middle and Upper Triassic evaporites and shales, and its relationship with the sedimentary cover and compressional structures. The information obtained from these methods was used to construct 2.5D and 3D models. These models indicate the significant role of compressional oblique structures and crestal weakening in the origin of the N-S salt-wall geometry, during the translation–rotation of the western end of the Sierras Marginales thrust sheet in the Late Eocene–Oligocene times. The uplift of low-density materials outlived compressional activity in the area and continued during the Oligocene–Early Miocene.