A thin‐skinned tectonics model for an arcuate fold and thrust belt: The Cantabrian Zone (Variscan Ibero‐Armorican Arc)

Abstract

The Cantabrian Zone constitutes the external zone of the Variscan orogenic belt in the northwest of the Iberian Peninsula. Within it a large number of thrusts and folds can be observed which define the form of the Asturian Arc. Tectonostratigraphically, two units can be distinguished: a pretectonic one and a syntectonic one. The time of the transition between the two units lies close to the Devonian‐Carboniferous boundary. The major allochthonous units of the Cantabrian Zone display varied geometries (duplexes, imbricated thrusts, out‐of‐sequence thrusts, etc.). The allochthonous units were emplaced in a foreland propagating sequence with movement age ranging from Westphalian B to Stephanian. Movement directions changed from one major unit. As a whole, the movement directions converge toward the core of the Asturian Arc, and are best interpreted in terms of a progressive series of rotational displacements, leading to a final disposition of major units similar to that of the leaves of a photographic iris. The folds were initiated at the same time as the motion of each nappe unit, and each type of structure represents the hanging wall adaptation to the development of a lateral and longitudinal staircase thrust surface topography. These folds suffered tightening after the emplacement of the thrust unit in which they occur, as a result of the different direction of movement of the next thrust unit propagating from beneath.

Plate kinematics in the Cantabrian domain of the Pyrenean orogen

“…Hercynian and Late Hercynian faults are wellpreserved, and were reactivated during both Mesozoic rifting and Cenozoic convergence stages (e.g. Pérez-Estaún et al, 1988;Lepvrier and Martínez-García, 1990;Pulgar et al, 1999;Alonso et al, 1996;Gutiérrez-Alonso et al, 2008). With the exception of the Cenozoic Duero Frontal Thrust, the major structures of the area, including the Ventaniella and Leon faults, have a Paleozoic age (Lepvrier and Martínez-García, 1990;Alonso et al, 2009 Ventaniella Fault crosses the entire Cantabrian Mountain Range, and its trace is exposed for more that 150 km.…”

Alpine tectonic wedging and crustal delamination in the Cantabrian Mountains (NW Spain)

“…The wellknown Variscan structure of the mountain range has been studied for a long time (e.g. Julivert, 1971;Pérez-Estaún et al, 1988;Dallmeyer and Martínez-García, 1990;Alonso et al, 2009), and more recent studies have focused on the Alpine structure Pulgar et al, , 1999Gallastegui, 2000;Gallastegui et al, 2002, Martín-González et al, 2011Pedreira et al, 2015). The Alpine history is directly related to the post-Variscan evolution of the North Iberian Margin, which started by a Permo-Triassic rifting stage that was followed by an approximately N-S extensional episode, triggered by the opening of the Atlantic Ocean and the Bay of Biscay during Late Jurassic and Early Cretaceous times.…”

A novel population of composite mounds: their initiation, growth and demise. San Emiliano Formation, Cantabrian Mountains, Spain

“…These units were based upon differences in facies associations, structural styles, metamorphism and magmatism (Lotze 1945). The northern most of these units is where the study area is located and is called the Cantabrian zone (Lotze 1945;Pérez-Estaún et al 1988). The Cantabrian zone consists of an incomplete Cambrian-Ordovician sedimentary sequence, a Silurian and Devonian sequence which is complete toward the west but is missing elsewhere and several thousand metres of strata spanning the Tournaisian to the Gzhelian Stages .…”

“…The Cantabrian zone consists of an incomplete Cambrian-Ordovician sedimentary sequence, a Silurian and Devonian sequence which is complete toward the west but is missing elsewhere and several thousand metres of strata spanning the Tournaisian to the Gzhelian Stages . The Cantabrian zone (Lotze 1945;Pérez-Estaún et al 1988) is further subdivided into five tectonic units: the Fold and Nappe, Central Asturian Coalfield, Ponga Nappe, Picos de Europa and Pisuerga-Carrión provinces. The San Emiliano Formation belongs to the La Sobia-Bodón/Aramo units of the Fold and Nappe Province (Pérez-Estaún et al 1988;Bahamonde et al 2002).…”

“…The Cantabrian zone (Lotze 1945;Pérez-Estaún et al 1988) is further subdivided into five tectonic units: the Fold and Nappe, Central Asturian Coalfield, Ponga Nappe, Picos de Europa and Pisuerga-Carrión provinces. The San Emiliano Formation belongs to the La Sobia-Bodón/Aramo units of the Fold and Nappe Province (Pérez-Estaún et al 1988;Bahamonde et al 2002). The formation was deposited within the foredeep depozone of a Variscan foreland basin.…”