Diagenesis of Pennsylvanian phylloid algal mounds from the southern Cantabrian Zone (Spain)

Abstract. The cross-correlation of ambient noise records registered by seismic networks has proven to be a valuable tool to obtain new insights into the crustal structure at different scales. Based on 2- to 14-s-period Rayleigh and Love dispersion data extracted from the seismic ambient noise recorded by 20 three-component broadband stations belonging to two different temporary experiments, we present the first i) upper crustal (1–14 km) high-resolution shear wave velocity and ii) radial anisotropy variation models of the continental crust in NW Iberia. The area of study represents one of the best exposed cross-sections along the Variscan orogen of western Europe, showing the transition between the external eastern zones towards the internal areas in the west. Both the 2-D maps and an E-W transect reveal a close correspondence with the main geological domains of the Variscan orogen. The foreland-fold and thrust-belt of the orogen, the Cantabrian Zone, is revealed by a zone of relatively low shear wave velocities (2.3–3.0 km/s), while the internal zones generally display higher homogeneous velocities (> 3.1 km/s). The boundary between both zones is clearly delineated in the models, depicting the arcuate shape of the orogen grain. The velocity patterns also reveal variations of the bulk properties of the rocks that can be linked to major Variscan structures, such as the basal detachment of the Cantabrian Zone or the stack of nappes involving pre-Variscan basement; or sedimentary features such as the presence of thick syn-orogenic siliciclastic wedges. Overall, the radial anisotropy magnitude varies between −5 and 15 % and increases with depth. The depth pattern suggests that the alignment of cracks is the main source of anisotropy at < 8 km depths, although the intrinsic anisotropy seems to be significant in the West-Asturian Leonese Zone, the low-grade slate belt adjacent to the Cantabrian Zone. At depths > 8 km, widespread high and positive radial anisotropies are observed, caused by the presence of subhorizontal alignments of grains and minerals in relation to the internal deformation of rocks either during the Variscan orogeny or prior to it.

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En el extremo de la Zona Cantábrica (Artículo de divulgación basado en una conferencia dictada por el autor, en Arbejal, Palencia, a profesores de Enseñanza Media) At the Cantabrian zone edge (Dissemination article based on a lecture given by the author, in Arbejal, Palencia, to Secondary Education teachers)

Trabajos de Geología ◽

10.17811/tdg.36.2016.163-190 ◽

2018 ◽

Vol 36 (36) ◽

pp. 163

Author(s):

Jenaro L. García-Alcalde

Keyword(s):

Secondary Education ◽

Variscan Orogeny ◽

Cantabrian Zone ◽

Secondary Education Teachers ◽

Zone Edge

Resumen: Se describe a grandes rasgos la evolución paleogeográfica y estructural y las condiciones tectonosedimentarias de la Zona Cantábrica, durante las etapas Variscas preorogénica y sinorogénica, con foco principal en la Provincia del Pisuerga-Carrión, y se detalla algo más la estratigrafía del Devónico de la región y las huellas que dejaron en las rocas de esta edad diferentes eventos geo-biológicos con elevado interés como herramientas cronoestratigráficas.Palabras clave: paleogeografía, evolución tectonosedimentaria, Zona Cantábrica, provincia del Pisuerga-Carrión, orogenia Varisca, Silúrico-Carbonífero.Abstract: An overall description of the Variscan paleogeography and tectonosedimentary evolution of the Pisuerga-Carrion Province (eastern Cantabrian Zone, N Spain) is given. The Devonian stratigraphy of that province and the major geologic and paleontological events recorded in these successions are briefly discussed, emphasizing their significance as chronostratigraphic tools.Keywords: paleogeography, tectonosedimentary evolution, Cantabrian Zone, Pisuerga-Carrion province, Variscan orogeny, Silurian-Carboniferous.

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The Geology and Isotope Geochemistry of the Talc Deposits ofPuebla de Lillo (Cantabrian Zone, Northern Spain)

Economic Geology ◽

10.2113/gsecongeo.95.6.1277 ◽

2000 ◽

Vol 95 (6) ◽

pp. 1277-1296

Author(s):

F. Tornos ◽

B. F. Spiro

Keyword(s):

Isotope Geochemistry ◽

Northern Spain ◽

Cantabrian Zone

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Algae, calcitarchs and the Late Ordovician Baltic limestone facies of the Baltic Basin

Facies ◽

10.1007/s10347-019-0585-0 ◽

2019 ◽

Vol 66 (1) ◽

Cited By ~ 1

Author(s):

Björn Kröger ◽

Amelia Penny ◽

Yuefeng Shen ◽

Axel Munnecke

Keyword(s):

Green Algae ◽

Carbonate Platform ◽

Late Ordovician ◽

Baltic Basin ◽

Low Latitude ◽

Fine Grained ◽

Baltic Countries ◽

The Baltic ◽

Algal Mounds ◽

Shallow Part

Abstract The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limestone, which is rich in calcareous green algae. This limestone occurs in surface outcrops and drill-cores in an extensive belt reaching from Sweden across the Baltic Sea to the Baltic countries. This limestone, which is known in the literature under several different lithological names, is described and interpreted, and the term “Baltic limestone facies” is suggested. The microfacies, from selected outcrops from the Åland Islands, Finland and Estonia, consists of calcareous green algae as the main skeletal component in a bioclastic mudstone-packstone lithology with a pure micritic matrix. Three types of calcitarch, which range in diameter from c. 100–180 μm, are common. Basinward, the youngest sections of the facies belt contain coral-stromatoporoid patch reefs and Palaeoporella-algal mounds. The Baltic limestone facies can be interpreted as representing the shallow part of an open-marine low-latitude carbonate platform.

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