Examinando por Autor "López-Mir, Berta"

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3D geometric reconstruction of Upper Cretaceous passive diapirs and salt withdrawal basins in the Cotiella Basin (southern Pyrenees)
(Journal of the Geological Society, 2016) López-Mir, Berta; García-Senz, Jesús; Muñoz, Josep Anton; López-Mir, Berta
High-quality images provided by 3D seismic surveys have transformed the interpretations of salt geometries in passive margins. Complementary field studies are needed to expand the ideas derived from seismic image interpretation. The Cotiella Basin exposes middle Coniacian–early Santonian basins developed by post-rift gravity-driven extension and passive diapirism in the proto-Atlantic Ocean. Salt-related sedimentary and structural features were preserved during the subsequent Pyrenean Orogeny, but the diapirs were squeezed to such a degree that they were completely destroyed. As a result, their influence on the development of the Cotiella Basin remains unclear. This paper presents a 3D geometric reconstruction of the extensional faults, the stratigraphic surfaces and the associated salt structures with the main objective of discussing the role of extension versus salt withdrawal. Our results indicate that the main Cotiella Basin was dominated by extensional faulting combined with along-strike salt migration, whereas the smaller Armeña, Mediodía and Seira basins were mainly dominated by salt withdrawal, involving the growth of passive diapirs, salt pillows and transfer faults. This is relevant because the described structures constitute an almost unique example to study in outcrop the structural style and kinematics of structures usually found offshore.
Early Mesozoic sinistral transpression along the Pai-Khoi–Novaya Zemlya fold–thrust belt, Russia
(Geological Society, London, Special Publications, 2018-01) Curtis, Michael L.; López-Mir, Berta; Scott, Robert A.; Howard, James P.
The NW–SE-trending Pai-Khoi fold–thrust belt links the Permian Uralian Orogen in the Polar Urals with the early Mesozoic fold belt on Novaya Zemlya. An interpretation of structural lineaments present in southern Novaya Zemlya suggests that the NW–SE-trending fold belt in southernmost Novaya Zemlya may have formed contemporaneously with parallel sinistral strike-slip faults. Analysis of regional-scale geological maps of the adjacent Pai-Khoi fold–thrust belt reveals large-scale structural relationships indicative of sinistral shear along the fold–thrust belt, including the presence of left-stepping en echelon folds within the Kara Shale Allochthon. This interpretation is corroborated by a field study of the allochthon-bounding Main Pai-Khoi Thrust, which reveals a consistently oblique tectonic stretching lineation, pitching 56° towards the east, suggesting tectonic displacement towards the west. It is therefore proposed that the Pai-Khoi fold–thrust belt is best described as a zone of sinistral inclined transpression. The interpretation of the Pai-Khoi fold–thrust belt as a zone of sinistral transpression has important implications for the interpretation of this tectonic boundary. This is reflected in a new structural cross-section through southernmost Novaya Zemlya, which is characterized by thick-skinned tectonics and steep strike-slip faults. These faults may link at depth with the Baidaratsky Fault.
Inhomogeneous rift inversion and the evolution of the Pyrenees
(Earth-Science Reviews, 2023-10) Pedrera, Antonio; García-Senz, Jesús; Pueyo, Emilio L.; López-Mir, Berta; Silva-Casal, Roi; Díaz-Alvarado, Juan
The kinematic evolution of the Pyrenees was largely controlled by structural and thermal heterogeneities inherited from a precursor rift system, resulting in complex along-strike variations in structural style and amount of shortening that remain a matter of debate. Based on a comprehensive compilation of published geological and geophysical data, this paper presents four newly-built sequentially restored cross-sections that make it possible to quantify the cumulative deformation along the Pyrenees and to assess the factors behind inhomogeneous lith ospheric shortening. In map-view, the cumulative shortening estimates are further constrained by regional vertical-axis rotations inferred from an extensive paleomagnetic dataset. Total shortening estimates reach maximum values of 125-122 km in the Central Pyrenees (Lannemezan and ECORS cross-sections, respectively) and diminish sideways, becoming 102 km in the Andorra cross-section, to the east, and 94 km in the Oloron ´ cross-section, to the west. To explain this shortening gradient, a new tectonic model with three key stages is proposed. (1) The onset of convergence took place during the Late Cretaceous, with the squeezing of a shallow asthenosphere and the extrusion of thinned crust pieces along the rift axis. (2) The dominant mechanism of deformation transitioned from squeezing to indentation during most of the Eocene, with the northern rift margin (European crust), including the thick exhumed lithospheric mantle, indenting into the weaker southern rifted margin (Iberian crust). The resulting bivergent orogenic wedge was heavily influenced by the lateral variability of the southern rifted margin geometry, with a long necking taper that narrows westward. (3) Crustal under thrusting, mostly operating in Priabonian-Aquitanian times, advanced steadily in the four studied cross-sections, with the strain gradually localizing into a single frontal basement thrust, which promoted incipient subduction. Frictional variations were greatly enhanced by thickness changes of the basal Upper Triassic salt unit, which favored a greater basement-cover decoupling in the Central Pyrenees, and explain the large-scale 20◦ clockwise vertical-axis rotations documented in the South-Western Pyrenees.
Seismic evidence for ductile necking of the mid-lower crust beneath the Columbrets Basin (Western Mediterranean)
(Terra Nova, 2023-10) Ramos, Adrià; Pedrera, Antonio; García-Senz, Jesús; López-Mir, Berta; Salas, Ramon
The Columbrets Basin is the largest Mesozoic rift basin of the Valencia Trough in the Western Mediterranean. The analysis of a seismic- reflection survey makes it possi-ble to reconstruct the tectonic fabric underlying the sedimentary basin, including the structure of the top of the lower crust and the Moho. It is proposed that the ductile deformation of the mid- lower crust was the main mechanism controlling the basin geometry, with the radial flow of mid- lower crust coeval with the reactivation of two large- offset SW-dipping normal faults, inherited from the precursor Permian–Triassic rifting. Mid- lower crustal necking occurred below the major depocenters, immedi-ately before hyperextension. Our results provide new insight into the formation of circular-shaped basins and the evolution of depth-dependent extensional processes during rifting.