El Paleozoico de les Guilleries

The Guilleries form a large massif of metasedimentary and igneous Paleozoic rocks, in the northern part of the Catalonian Coastal Ranges. The oldest rocks croping out have been considered as Cambrian-Early Ordovician. They consist of two lithostratigraphical units separated by a laminar body of orthogneises, several hundred meters thick. The lower unit (Osor Formation) is essentially metapelitic, with a horizon of orthoamphibolites up to 50 m thick. The upper unit (Susqueda Formation) is also essentially metapelitic, but it shows a thick marble horizon near its base, a few meters above the top of the gneisses. The existence of this marble horizon has been traditionally taken as an argument to support the Cambrian age. Stratigraphically higher, there is a volcano-clastic sequence, containing acid volcanic horizons, in which Caradoc brachiopods have been collected. Silurian and Devonian rocks also crop out in the area although very incomplete due to faulting. The whole sequence was folded and metamorphosed during the Hercynian orogeny. The deformation is polyphasic, the deeper zones show a gently diping schistosity which shows to be the result of the crenulation of an older foliation. In the shallower crustal levels the dominant foliation is a slaty cleavage. All rocks exposed in the area have been affected by the Hercynian metamorphism. The deep seated levels show an amphibolite facies metamorphism, with cordierite and K-feldspar in pelites. In the shallower zones green-schist facies rocks with chlorite prevail in pelites. Several intrusive events, with the emplacement of different types of granitoids can be evidenced. The oldest, are represented by deformed diorite and quartzdiorite dykes. Later on two-mica leucogranites were emplaced. coinciding with the higher-grade zones. These granites are also deformed, at least in some localities. Finally, late tectonic granitoids were emplaced inducing a contact metamorphism, particularly clear where they reach high structural levels

El Paleozoico de les Guilleries

The Guilleries form a large massif of metasedimentary and igneous Paleozoic rocks, in the northern part of the Catalonian Coastal Ranges. The oldest rocks croping out have been considered as Cambrian-Early Ordovician. They consist of two lithostratigraphical units separated by a laminar body of orthogneises, several hundred meters thick. The lower unit (Osor Formation) is essentially metapelitic, with a horizon of orthoamphibolites up to 50 m thick. The upper unit (Susqueda Formation) is also essentially metapelitic, but it shows a thick marble horizon near its base, a few meters above the top of the gneisses. The existence of this marble horizon has been traditionally taken as an argument to support the Cambrian age. Stratigraphically higher, there is a volcano-clastic sequence, containing acid volcanic horizons, in which Caradoc brachiopods have been collected. Silurian and Devonian rocks also crop out in the area although very incomplete due to faulting. The whole sequence was folded and metamorphosed during the Hercynian orogeny. The deformation is polyphasic, the deeper zones show a gently diping schistosity which shows to be the result of the crenulation of an older foliation. In the shallower crustal levels the dominant foliation is a slaty cleavage. All rocks exposed in the area have been affected by the Hercynian metamorphism. The deep seated levels show an amphibolite facies metamorphism, with cordierite and K-feldspar in pelites. In the shallower zones green-schist facies rocks with chlorite prevail in pelites. Several intrusive events, with the emplacement of different types of granitoids can be evidenced. The oldest, are represented by deformed diorite and quartzdiorite dykes. Later on two-mica leucogranites were emplaced. coinciding with the higher-grade zones. These granites are also deformed, at least in some localities. Finally, late tectonic granitoids were emplaced inducing a contact metamorphism, particularly clear where they reach high structural levels

Paleozoic stratigraphy of the Central and Northern part of the Catalonian Coastel Ranges (NE Spain)

The Paleozoic stratigraphic succession in the Catalonian Coastal Ranges spans the interval from Cambrian(?) to Carboniferous, with only one break, separating the pre-Carboniferous part of the sequence from the Carboniferous. The oldest rocks exposed form a sequence of schists, fine grained sandstones, gneisses (laminar pre-Hercynian intrusions), marbles, orto- and para-amphibolites and calcsilicate rocks. comparison with other localities iuggests an Early Cambrian age (or perhaps in part older). Upwards the sequence becomes more monotonous andconsists only of schists (or slates where themetamorphic grade is lower) and thin fine-grained sandstone layers (Cambrian- Ordovician). Still higher in the sequence, an altemation of greywackes and slates is found, with interlayered mud-supported conglomerates at its lower part and acid volcanic rocks which occur throughout the whole sequence. This part of the sequence has provided the oldest faunas known in the Catalonian Coastal Ranges, which indicate the Caradoc. Finally, in its uppermost part, the Ordovician sequence contains some thin limestone layers that contain Ashgill faunas. The Silurian, from Llandovery to Lower Ludlow, consists of black graptolitic shales with dolerite sills, whilst the upper Ludlow, Pridolian and Devonian consist of nodular limestones and marls withpelagic and hemipelagic faunas. The youngest Devonian faunas found correspond in general to the Emsian. The existence of a gap at this point of the sequence suggests the possibility that part of the Devonian could have been eroded. The Carboniferous is characterized by a thick culm sequence (Visean to Westphalian?), resting on thin chert and limestone layers (Tournaisian and Visean). A comparisonwith neighbouring areas shows a similarity regarding succession and facies with other Paleozoic massifs around the Western Mediterranean

The Hercynian structure of the Catalonian Coastel Ranges (NE Spain)

In the Catalonian Coastal Ranges, Paleozoic sedimentary and meta-sedimentary rocks crop out in several areas, intruded by late tectonic Hercynian granitoids and separated by Mesozoic and Tertiary cover sediments. Large structures are often difficult to recognize, although a general east-west trend can be observed on the geological map. Deformation was accompanied by the development of cleavages and regional metamorphism. Green-schist facies rocks are prominent throughout the Ranges, while amphibolite facies are restricted to small areas. In low-grade areas, the main deformation phase generated south-facing folds with an axial plane cleavage (slaty cleavage in metapelitic rocks). The intersection lineation (Ss/Sl) and the axes of minor folds trend cast-west, as do all mapable structures. Late deformations generated coarse crenulations, small chevrons and kink-bands, all intersecting the slaty cleavage at high angles. In medium- to high-grade areas no major folds have been observed. In these areas, the main foliation is a schistosity and is often folded, giving centimetric to decimetric, nearly isoclinal intrafolial folds. In schists, these folds aremuchmore common than inother lithologies, and can be associated with a crenulation cleavage. All these planar structures in high-grade rocks are roughly parallel. The late Hercynian deformational events, which gave rise to the crenulations and small chevrons, also produced large (often kilometric) open folds which fold the slaty cleavage and schistosity. As aconsequence, alternating belts with opposite dip (north and south) of the main foliation were formed. With respect to the Hercynian orogenic belt, the Paleozoic outcrops of the Catalonian Coastal Ranges are located within the northern branch of the Ibero-Armorican arc, and have a relatively frontal position within the belt. The Carboniferous of the Priorat- Prades area, together with other outcrops in the Castellón Province, the Montalbán massif (Iberian Chain) and the Cantabrian zone (specially the Pisuerga-Carrión Province) probably form part of a wide area of foreland Carboniferous deposition placed at the core of the arc

The Hercynian structure of the Catalonian Coastel Ranges (NE Spain)

In the Catalonian Coastal Ranges, Paleozoic sedimentary and meta-sedimentary rocks crop out in several areas, intruded by late tectonic Hercynian granitoids and separated by Mesozoic and Tertiary cover sediments. Large structures are often difficult to recognize, although a general east-west trend can be observed on the geological map. Deformation was accompanied by the development of cleavages and regional metamorphism. Green-schist facies rocks are prominent throughout the Ranges, while amphibolite facies are restricted to small areas. In low-grade areas, the main deformation phase generated south-facing folds with an axial plane cleavage (slaty cleavage in metapelitic rocks). The intersection lineation (Ss/Sl) and the axes of minor folds trend cast-west, as do all mapable structures. Late deformations generated coarse crenulations, small chevrons and kink-bands, all intersecting the slaty cleavage at high angles. In medium- to high-grade areas no major folds have been observed. In these areas, the main foliation is a schistosity and is often folded, giving centimetric to decimetric, nearly isoclinal intrafolial folds. In schists, these folds aremuchmore common than inother lithologies, and can be associated with a crenulation cleavage. All these planar structures in high-grade rocks are roughly parallel. The late Hercynian deformational events, which gave rise to the crenulations and small chevrons, also produced large (often kilometric) open folds which fold the slaty cleavage and schistosity. As aconsequence, alternating belts with opposite dip (north and south) of the main foliation were formed. With respect to the Hercynian orogenic belt, the Paleozoic outcrops of the Catalonian Coastal Ranges are located within the northern branch of the Ibero-Armorican arc, and have a relatively frontal position within the belt. The Carboniferous of the Priorat- Prades area, together with other outcrops in the Castellón Province, the Montalbán massif (Iberian Chain) and the Cantabrian zone (specially the Pisuerga-Carrión Province) probably form part of a wide area of foreland Carboniferous deposition placed at the core of the arc

Paleozoic stratigraphy of the Central and Northern part of the Catalonian Coastel Ranges (NE Spain)

The Paleozoic stratigraphic succession in the Catalonian Coastal Ranges spans the interval from Cambrian(?) to Carboniferous, with only one break, separating the pre-Carboniferous part of the sequence from the Carboniferous. The oldest rocks exposed form a sequence of schists, fine grained sandstones, gneisses (laminar pre-Hercynian intrusions), marbles, orto- and para-amphibolites and calcsilicate rocks. comparison with other localities iuggests an Early Cambrian age (or perhaps in part older). Upwards the sequence becomes more monotonous andconsists only of schists (or slates where themetamorphic grade is lower) and thin fine-grained sandstone layers (Cambrian- Ordovician). Still higher in the sequence, an altemation of greywackes and slates is found, with interlayered mud-supported conglomerates at its lower part and acid volcanic rocks which occur throughout the whole sequence. This part of the sequence has provided the oldest faunas known in the Catalonian Coastal Ranges, which indicate the Caradoc. Finally, in its uppermost part, the Ordovician sequence contains some thin limestone layers that contain Ashgill faunas. The Silurian, from Llandovery to Lower Ludlow, consists of black graptolitic shales with dolerite sills, whilst the upper Ludlow, Pridolian and Devonian consist of nodular limestones and marls withpelagic and hemipelagic faunas. The youngest Devonian faunas found correspond in general to the Emsian. The existence of a gap at this point of the sequence suggests the possibility that part of the Devonian could have been eroded. The Carboniferous is characterized by a thick culm sequence (Visean to Westphalian?), resting on thin chert and limestone layers (Tournaisian and Visean). A comparisonwith neighbouring areas shows a similarity regarding succession and facies with other Paleozoic massifs around the Western Mediterranean

Hercynian Metamorphism in the Catalonian Coastel Ranges

Paleozoic rocks in the Catalonian Coastal Ranges are in their largest part affectedby alow- tovery-low grade Hercynian metamorphism. Amphibolite facies conditions are only found in restricted areas such as the southwestern part of the Guilleries massif where upper amphibolite facies conditions are reached. Metamorphic grade increases from top to bottom of the Paleozoic stratigraphic sequence and the metamorphic peak is diachronous, being progressively older in the lower grade metamorphic zones. The isograd pattern, mineral assemblages, mineral chemistry and preserved reaction textures are consistent with a low pressure metamorphism possibly evolving from a previous Barrovian type event. The metamorphic climax in the high grade zone was reached after the seconddeformational phase. Calculatedpeak P-Tconditions are 620-640 OC and around 3.5 Kb . A latter episode of decompression from the maximum conditions to 1-2 Kb, with an associated temperature decrease to 530-550 OC, is recognized. The intrusion of late Hercynian granitoids produced contact metamorphic aureoles where the pyroxene-hornfels facies is locally reached