Early Ordovician–Devonian Passive Margin Stage in the Gondwanan Units of the Iberian Massif

Gutiérrez-Marco, J. C.; Piçarra, José Manuel; Meireles, Carlos; Cózar, Pedro; García‐Bellido, Diego C.; Pereira, Zélia; Vaz, Nuno; Pereira, Sofía; Lopes, Gilda; Oliveira, José Tomás; Quesada, Cecilio; Zamora, Samuel; Esteve, Jorge; Colmenar, Jorge; Bernárdez, Enrique; Coronado, Ismael; Lorenzo, Saturnino; Sá, Artur A.; Silva, Í. Dias da; Clavijo, Emílio González; Montes, Alejandro Díez; Gómez-Barreiro, Juan

doi:10.1007/978-3-030-10519-8_3

Cited by 28 publications

(22 citation statements)

References 82 publications

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“…The Gondwanan affinity autochthonous units of the Iberian Massif are primarily composed of amalgamated Neoproterozoic terranes (Quesada, 1991;Shelley and Bossière, 2000;Martínez Catalán et al, 2004;Nance et al, 2010) that are unconformably overlain by Cambrian rift-related successions (ca 530-490 Ma; Sánchez-García et al, 2019 and references therein). The syn-rift successions are overlain by sedimentary rocks recording a rift-to-drift transition and subsidence (Pérez Estaún et al, 1990), which resulted in passive margin conditions on the northern margin of Gondwana that persisted until the onset of the Variscan orogeny in Early Devonian times (Gutiérrez-Marco et al, 2019). A Furongian (ca 497-485 Ma) break-up unconformity is interpreted to have formed as the Avalonia microcontinent separated from…”

Section: Stratigraphymentioning

confidence: 99%

Ordovician ironstone of the Iberian margin: Coastal upwelling, ocean anoxia and Palaeozoic biodiversity

Pufahl

Squires

Murphy

et al. 2020

The Depositional Record

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Middle to Upper Ordovician ironstone and associated sedimentary rocks of the West Asturian‐Leonese and Cantabrian tectonostratigraphic zones, Spain, provide new information regarding the Palaeozoic Fe cycle and the palaeoceanography of the Rheic Ocean. Examination of drill cores and outcrops indicates the southeastern margin of this narrow seaway was a dynamic continental shelf where upwelling of ferruginous seawater and storm currents controlled lithofacies character. Parasequence composition and stacking relationships suggest ironstone accumulated during marine transgression as accommodation increased from lowstand conditions. Proximal parasequences record aggradation from deep subtidal to shoreface environments. Hummocky cross‐stratified sandstone and organic‐rich siltstone grade upwards into swaley cross‐stratified sandstone and granular Fe‐silicate‐rich ironstone capped by a flooding surface. Distal parasequences were deposited below storm wave base on the distal shelf and are composed of variably bioturbated organic‐rich siltstone with thin Fe‐chlorite and phosphorite layers. These differences in parasequence character define two different ironstone factories where Fe was concentrated and precipitated in sediment. Lithofacies associations support an emerging model for ironstone deposition where coastal upwelling delivered and stimulated the precipitation of Fe within shelf sediment. This notion provides further evidence for the development of intermittent anoxic water masses in an Ordovician ocean that was near the threshold of becoming fully ventilated. This style of Fe delivery probably represents a tipping point in the oxygenation history of the Phanerozoic oceans and is a throwback to the Precambrian when widespread anoxia allowed hydrothermal Fe to concentrate in the global ocean. New data suggest that minor extinction events punctuating the Great Ordovician Biodiversification Event may be traced to these anoxic waters, which in addition to Fe, were also enriched in biologically toxic, redox sensitive trace elements. Conversely, precipitation of upwelling‐related ironstone may have helped sequester these trace elements, providing a negative feedback response that would aid post‐extinction recovery.

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Section: Stratigraphymentioning

confidence: 99%

Ordovician ironstone of the Iberian margin: Coastal upwelling, ocean anoxia and Palaeozoic biodiversity

Pufahl

Squires

Murphy

et al. 2020

The Depositional Record

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“…The Gondwanan autochthonous stratigraphy (Cantabrian, West Asturian-Leonese, Central Iberian, and Ossa-Morena zones) consists of a Neoproterozoic arc and back-arc basin (e.g., Fernández-Suárez et al, 2014), which evolved to a rift-to-drift Cambrian to early Ordovician sequence and then to an Ordovician to late Devonian passive margin basin sequence (e.g., Sánchez-García et al, 2019;Gutiérrez-Marco et al, 2019;Gutiérrez-Alonso et al, 2020). Overall the system transitioned from a relatively isolated early Cambrian continental basin to a restricted marine basin and to the development of an open marine platform that was locally punctuated by magmatism (e.g., Gutiérrez-Alonso et al, 2008b;Palero-Fernández, 2015).…”

Section: Two Of Us: the Variscan Orogen In Iberiamentioning

confidence: 99%

“…The Ossa-Morena Zone represents the outermost platform, followed by an intermediate platform characterized by an asymmetric horst (Central Iberian Zone) and graben (West Asturian-Leonese Zone), which ends in the innermost shelf environment of the Cantabrian Zone ( Fig. 3; e.g., Gutiérrez-Marco et al, 2019). The differences between the West Asturian-Leonese and Central Iberian zones are mainly deeper versus shallower sedimentary facies (respectively) and a local Lower Ordovician unconformity in the Central Iberian Zone (Toledanian; e.g., Álvaro et al, 2018), which places Lower Ordovician strata atop pre-Cambrian to Cambrian rocks ( Fig.…”

Section: Two Of Us: the Variscan Orogen In Iberiamentioning

confidence: 99%

“…The differences between the West Asturian-Leonese and Central Iberian zones are mainly deeper versus shallower sedimentary facies (respectively) and a local Lower Ordovician unconformity in the Central Iberian Zone (Toledanian; e.g., Álvaro et al, 2018), which places Lower Ordovician strata atop pre-Cambrian to Cambrian rocks ( Fig. 3; e.g., Gutiérrez-Marco et al, 2019). The Central Iberian Zone is divided into two domains: (1) the Ollo de Sapo domain, which contains abundant lower Ordovician magmatism of calc-alkaline affinity (e.g., Montes, 2007;Gutiérrez-Marco et al, 2019); and (2) the "Schistose-Greywacke domain" characterized by a predominance of outcrops of Neoproterozoic to lower Cambrian sedimentary rocks (e.g., Gutiérrez-Marco et al, 2019, and references therein).…”

Section: Two Of Us: the Variscan Orogen In Iberiamentioning

confidence: 99%

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The enigmatic curvature of Central Iberia and its puzzling kinematics

2020

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Abstract. The collision between Gondwana and Laurussia that formed the latest supercontinent, Pangea, occurred during Devonian to early Permian times and resulted in a large-scale orogeny that today transects Europe, northwest Africa, and eastern North America. This orogen is characterized by an “S” shaped corrugated geometry in Iberia. The northern curve of the corrugation is the well-known and studied Cantabrian (or Ibero–Armorican) Orocline and is convex to the east and towards the hinterland. Largely ignored for decades, the geometry and kinematics of the southern curvature, known as the Central Iberian curve, are still ambiguous and hotly debated. Despite the paucity of data, the enigmatic Central Iberian curvature has inspired a variety of kinematic models that attempt to explain its formation but with little consensus. This paper presents the advances and milestones in our understanding of the geometry and kinematics of the Central Iberian curve from the last decade with particular attention to structural and paleomagnetic studies. When combined, the currently available datasets suggest that the Central Iberian curve did not undergo regional differential vertical-axis rotations during or after the latest stages of the Variscan orogeny and did not form as the consequence of a single process. Instead, its core is likely a primary curve (i.e., inherited from previous physiographic features of the Iberian crust), whereas the curvature in areas outside the core is dominated by folding interference from the Variscan orogeny or more recent Cenozoic (Alpine) tectonic events.

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“…1A-B), the so-called Toledanian Phase is recognized as an angular discordance that separates variably tilted Ediacaran-Cambrian Series 2 rifting volcanosedimentary packages from overlying passive-margin successions. The Toledanian gap comprises, at least, most of the Furongian and basal Ordovician, but the involved erosion can incise into the entire Cambrian and the upper Ediacaran Cadomian basement (Gutiérrez-Marco et al, 2019;Álvaro et al, 2019;Sánchez-García et al, 2019).…”

Section: Central Iberian and Galicia-trás-os-montes Zonesmentioning

confidence: 99%

Comparative geochemical study on Furongian (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe

Álvaro¹,

Sánchez-García²,

Puddu³

et al. 2020

Preprint

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Abstract. A geochemical comparison of Early Palaeozoic felsic magmatic episodes throughout the south-western European margin of Gondwana is analysed. The comparison is made between (i) Furongian–Early Ordovician (Toledanian) activies recorded in the Central Iberian and Galicia-Trás-os-Montes Zones of the Iberian Massif, and (ii) Early–Late Ordovician (Sardic) activities in the eastern Pyrenees, Occitan Domain (Albigeois, Montagne Noire and Mouthoumet massifs) and Sardinia. Both phases are related to uplift and denudation of an inherited palaeorelief, and stratigraphically preserved as distinct angular discordances and paraconformities involving gaps of up to 30 m.y. The geochemical features of the Toledanian and Sardic, felsic-dominant activies point to a predominance of byproducts derived from the melting of metasedimentary rocks, rich in SiO2 and K2O and with peraluminous character. Zr / TiO2, Zr / Nb, Nb / Y and Zr vs. Ga / Al ratios, and REE and ƐNd values suggest the contemporaneity, for both phases, of two geochemical scenarios characterized by arc and extensional features evolving to distinct extensional and rifting conditions associated with the final outpouring of mafic tholeiitic-dominant lava flows. The Toledanian and Sardic phases are linked to neither metamorphism nor penetrative deformation; on the contrary, their unconformities are associated with foliation-free open folds subsequently affected by the Variscan deformation. The geochemical and structural framework precludes a subduction scenario reaching the crust in a magmatic arc to back-arc setting, but favours partial melting of sediments and/or granitoids in a continental lower crust triggered by the underplating of hot mafic magmas during extensional events related to the opening of the Rheic Ocean.

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Early Ordovician–Devonian Passive Margin Stage in the Gondwanan Units of the Iberian Massif

Cited by 28 publications

References 82 publications

Ordovician ironstone of the Iberian margin: Coastal upwelling, ocean anoxia and Palaeozoic biodiversity

Ordovician ironstone of the Iberian margin: Coastal upwelling, ocean anoxia and Palaeozoic biodiversity

The enigmatic curvature of Central Iberia and its puzzling kinematics

Comparative geochemical study on Furongian (Toledanian) and Ordovician (Sardic) felsic magmatic events in south-western Europe

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