Constraints Imposed by Rift Inheritance on the Compressional Reactivation of a Hyperextended Margin: Mapping Rift Domains in the North Iberian Margin and in the Cantabrian Mountains

Abstract During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

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Subduction-related structures in the North Iberian Margin

Journal of Geophysical Research Atmospheres ◽

10.1029/97jb01425 ◽

1997 ◽

Vol 102 (B10) ◽

pp. 22497-22511 ◽

Cited By ~ 71

Author(s):

J. Alvarez-Marron ◽

E. Rubio ◽

M. Torne

Keyword(s):

The North ◽

Iberian Margin

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Investigating the role of the Galicia Bank on the formation of the North West Iberian margin using deformable plate tectonic models

Tectonophysics ◽

10.1016/j.tecto.2020.228537 ◽

2020 ◽

Vol 789 ◽

pp. 228537

Author(s):

Michael T. King ◽

J. Kim Welford ◽

Alexander L. Peace

Keyword(s):

Plate Tectonic ◽

North West ◽

The North ◽

Iberian Margin

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The architecture and the multi-stage evolution of the North Iberian margin (Bay of Biscay)

10.5194/egusphere-egu2020-3964 ◽

2020 ◽

Author(s):

Patricia Cadenas ◽

Gianreto Manatschal ◽

Gabriela Fernández-Viejo

Keyword(s):

Rift System ◽

Plate Boundaries ◽

Bay Of Biscay ◽

Velocity Models ◽

The North ◽

Rifted Margins ◽

Multi Stage ◽

Stratigraphic Architecture ◽

Half Graben ◽

Iberian Margin

In this work, we address the problem of the formation and reactivation of multi-stage rifting based on the study of the central North Iberian margin, located at the southern Bay of Biscay triangular oceanic domain. This magma-poor rifted margin registered three major Mesozoic rift events and a subsequent Alpine compressional reactivation, representing a unique setting to study the architecture of a multi-stage rift system and its control on subsequent reactivation. Based on a dense dataset of high quality 2D seismic reflection profiles, boreholes and published velocity models, we define, describe and map structural domains, major extensional and compressional structures, and the depth and thickness of syn-rift units. We provide new structural maps showing the geometry and spatial distribution of major rift basins and bounding structures.The analysis of the tectono-stratigraphic architecture led us to define three rift systems. A diffuse and widespread of Triassic age, with classical fault-bounded half-graben basins, a second, narrow, deep and localised Late Jurassic to Barremian transtensional system, and a third, widely distributed Aptian to Cenomanian hyperextended system, including two distinctive domains. Our results show that each rift system controlled successive rift events, and that the stacking and overlap of the three rift systems resulted in a complex and segmented 3D template that guided subsequent compressional reactivation. Compression affected on a distinctive way the three rift systems, leading to an amplification of the margin segmentation.This work shows that unravelling the tectono-stratigraphic architecture and evolution of multi-stage rift systems can provide key insights not only to decipher the spatial and temporal evolution of divergent plate boundaries, but also to set up present-day kinematic templates to test dynamic plate deformable models of conjugate rifted margins. It will also be a keystone to constrain early stages of margin reactivation and the architecture of reactivated rifted margins now incorporated in orogenic systems.

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Control litológico y estructural de los deslizamientos en el monte Rodiles (Asturias, España) Lithological and structural control of landslides in the Rodiles Hill (Asturias, Spain)

Trabajos de Geología ◽

10.17811/tdg.36.2016.279-296 ◽

2018 ◽

Vol 36 (36) ◽

pp. 279

Author(s):

S. Llana Fúnez

Keyword(s):

Structural Control ◽

Thick Layer ◽

Normal Fault ◽

Reverse Fault ◽

Cantabrian Mountains ◽

The North ◽

Jurassic Rock ◽

Para Determinar ◽

Historic Settlement ◽

The Hill

Resumen: El monte Rodiles, situado en el margen oriental de la ría de Villaviciosa, conserva evidencias de ocupación histórica desde sus orígenes como castro romanizado. El asentamiento está limitado en su vertiente sur por los restos de una muralla defensiva, mientras que en la ladera nororiental existen escarpes rocosos que debieron de actuar como defensa del enclave. Este trabajo realiza un análisis del relieve y revisa la estructura del sustrato geológico en el entorno próximo para determinar el origen de los escarpes en la ladera nordeste. Los datos de campo y el análisis de la topografía permiten identificar la existencia de varios deslizamientos que afectan a gran parte de la ladera nororiental del monte Rodiles. La masa deslizada aprovecha la inclinación de la sucesión litológica del Jurásico hacia el NE. La existencia de un nivel de arcillas, mecánicamente incompetentes, por debajo de los conglomerados de la Formación La Ñora, mecánicamente más competentes, permite el movimiento de la ladera hacia el mar. Estos escarpes están además alineados con la terminación lateral de una falla normal Mesozoica reactivada posteriormente como una falla inversa durante el levantamiento de la Cordillera Cantábrica. Las cicatrices de los deslizamientos, desarrolladas sobre niveles métricos de conglomerados fracturados, constituyeron por tanto una defensa natural del enclave histórico.Palabras clave: enclave histórico, deslizamientos, estabilidad de taludes, conglomerados jurásicos.Abstract: The Rodiles hill, on the eastern shores of the Villaviciosa estuary, preserves evidences of historic occupation since the romans. The settlement has a defensive wall in the south and is bounded to the north by a cragged slope to the sea. This work investigates the relief and the structure of the rocks in the area aiming at finding an origin for the crags in the northeastern slope of the hill. Field observations and the analysis of the topography reveal the presence of several landslides that affect most of the northeastern hillside. The dip of the Jurassic rock sequence to the NE and the presence of a two meter-thick layer of shales, mechanically very plastic, below the La Ñora conglomerates Formation, mechanically very competent, favours the slip of the hillside. The scarps are aligned with the lateral termination of a Mesozoic normal fault, reactivated as a reverse fault during the formation of the Cantabrian Mountains. The head scarps at the back of the landslides, developed on fractured conglomerates, constituted a natural defence during the historic settlement.Keywords: historic settlement, slides, slope stability, Jurassic conglomerates.

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Ambient noise tomography of the Central Cantabrian Mountains (NW Spain). New insights from the GEOCANTABRICA-COSTA seismic network.

10.5194/egusphere-egu2020-19420 ◽

2020 ◽

Author(s):

Jorge Acevedo ◽

Gabriela Fernández-Viejo ◽

Sergio Llana-Fúnez ◽

Carlos López-Fernández ◽

Luis Pando ◽

...

Keyword(s):

Ambient Noise ◽

Body Wave ◽

Processing Technique ◽

Ambient Noise Tomography ◽

Cantabrian Mountains ◽

Nw Spain ◽

The West ◽

The North ◽

New Information ◽

Nucleation Sites

The Cantabrian Mountains (NW Spain) are an Alpine chain that was formed as a result of the collision between Iberia and Europe in the Cenozoic. In their central sector, the uplift of the orogen led to the exhumation of a block of Variscan -Paleozoic- basement, the reactivation of Variscan structures and the formation of new E-W oriented fractures. Moreover, the formation of the Cantabrian Mountains involved the development of a crustal root with a thickness of 45-55 km that decreases up to 30-35 km towards the west. The thickening occurs preferentially in the crust that had previously been extended during the two main rifting episodes that affected this area in the Mesozoic. At the surface, the limit between the normal and the thickened crust roughly coincides with the trace of the Ventaniella fault, a subvertical crustal structure that runs for more than 400 km both inland and offshore. In order to obtain new insights from this complex region, it was installed a network (GEOCANT&#193;BRICA-COSTA, doi:10.7914/SN/YR_2019) of 13 broadband stations covering an area of 160x80 km (~40 km spacing) for 8 months. The phase cross-correlation (PCC) processing technique was used to cross-correlate daily records of the 78 station pairs. After stacking the cross-correlograms, the empirical Green&#8217;s functions and the dispersion curves were obtained. Finally, a Rayleigh wave group velocity tomography was performed, retrieving the seismic signature of the Variscan crust and allowing us to extend to the north our previous seismic ambient noise tomography and complete the tomographic model of the central Cantabrian Mountains. To reveal the structure beneath the seismic stations, we also performed ambient noise auto-correlations, successfully retrieving body-wave reflections from the crust-mantle boundary that provide new information about the limits of the crustal root. The study area presents a lingering, low-magnitude intraplate seismic activity that increases from east to west and extends into the continental shelf. The Ventaniella fault also acts as a seismic barrier to the propagation of earthquakes towards the east while provides nucleation sites along its trace. Thus, another objective of this study was to detect and relocate the local seismicity of the Cantabrian Mountains and the Cantabrian margin activity in particular. Our preliminary catalogue of events, obtained from the automatic analysis of the real-time seismic data with SeiscompP3, comprises 54 local earthquakes. Seven of them have their epicentres in the Cantabrian margin and, as expected, all were located to the west of the Ventaniella fault.

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Reply to Comment by Pedreira et al. on “Reconstruction of the Exhumed Mantle Across the North Iberian Margin by Crustal‐Scale 3‐D Gravity Inversion and Geological Cross Section”

Tectonics ◽

10.1029/2018tc005222 ◽

2018 ◽

Vol 37 (11) ◽

pp. 4346-4356 ◽

Cited By ~ 3

Author(s):

A. Pedrera ◽

J. García‐Senz ◽

C. Ayala ◽

A. Ruiz‐Constán ◽

L. R. Rodríguez‐Fernández ◽

...

Keyword(s):

Cross Section ◽

Gravity Inversion ◽

The North ◽

Geological Cross Section ◽

Iberian Margin

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Millennial-scale climatic variability between 340 000 and 270 000 years ago in SW Europe: evidence from a NW Iberian margin pollen sequence

Climate of the Past ◽

10.5194/cp-5-53-2009 ◽

2009 ◽

Vol 5 (1) ◽

pp. 53-72 ◽

Cited By ~ 35

Author(s):

S. Desprat ◽

M. F. Sánchez Goñi ◽

J. F. McManus ◽

J. Duprat ◽

E. Cortijo

Keyword(s):

Climatic Variability ◽

Interglacial Period ◽

Vegetation Changes ◽

Pollen Record ◽

Cold Event ◽

Ice Volume ◽

The North ◽

Nw Iberia ◽

Iberian Margin ◽

Millennial Scale

Abstract. We present a new high-resolution marine pollen record from NW Iberian margin sediments (core MD03-2697) covering the interval between 340 000 and 270 000 years ago, a time period centred on Marine Isotope Stage (MIS) 9 and characterized by particular baseline climate states. This study enables the documentation of vegetation changes in the north-western Iberian Peninsula and therefore the terrestrial climatic variability at orbital and in particular at millennial scales during MIS 9, directly on a marine stratigraphy. Suborbital vegetation changes in NW Iberia in response to cool/cold events are detected throughout the studied interval even during MIS 9e ice volume minimum. However, they appear more frequent and of higher amplitude during the 30 000 years following the MIS 9e interglacial period and during the MIS 9a-8 transition, which correspond to intervals of an intermediate to high ice volume and mainly periods of ice growth. Each suborbital cold event detected in NW Iberia has a counterpart in the Southern Iberian margin SST record. High to moderate amplitude cold episodes detected on land and in the ocean appear to be related to changes in deep water circulation and probably to iceberg discharges at least during MIS 9d, the mid-MIS 9c cold event and MIS 9b. This work provides therefore additional evidence of pervasive millennial-scale climatic variability in the North Atlantic borderlands throughout past climatic cycles of the Late Pleistocene, regardless of glacial state. However, ice volume might have an indirect influence on the amplitude of the millennial climatic changes in Southern Europe.

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