ALBERT

Description: The structures in the SW part of the Cantabrian Mountains have much in common with those of the Foothills Belt of the Rocky Mountains, the Alps and the Central European Hercynian orogene, and their origin can be explained in the same way as that of the structures in these orogenes. The greywacke sedimentation and the folding both migrated from the internal to the external part of the original basin during the Upper Carboniferous. The folds and thrust faults run parallel to the axis of the original basin. The basement has been broken into large blocks in the shape of parallelograms, along the boundary faults of which local deviations of the regional directions occurred.

Description: The structures in the SW part of the Cantabrian Mountains have much in common with those of the Foothills Belt of the Rocky Mountains, the Alps and the Central European Hercynian orogene, and their origin can be explained in the same way as that of the structures in these orogenes. The greywacke sedimentation and the folding both migrated from the internal to the external part of the original basin during the Upper Carboniferous. The folds and thrust faults run parallel to the axis of the original basin. The basement has been broken into large blocks in the shape of parallelograms, along the boundary faults of which local deviations of the regional directions occurred.

Description: The present map is the continuation of the map published by De Sitter in 1962. The folded Precambrian basement in this area is overlain unconformably by Cambrian up to Carboniferous strata. The Palaeozoic has been uplifted during the Bretonic phase, and folded during the Sudetic, Asturian, and Saalic phases. In the western end of the Le\xc3\xb3nides the structures known from the eastern part of the Luna unit do not continue but are replaced bij one syncline and a number of thrusts. Major block faulting of the basement determined the curved structure of the ""Asturian Knee"" and also the diverse contemporaneous directions of thrusting and folding. Thinly developed Devonian of the Caldas Formation demonstrates the presence of a structural ridge early during the sedimentation. Stephanian intramontane basins developed along faults in downwarped areas.

Description: After a late-Precambrian folding, clastic deposits, partly continental, spread out over the region during the Lower Cambrian; later, marine intercalations became more abundant when upper Lower Cambrian marine sediments were deposited. This sedimentation continued until the Upper Carboniferous and occurred on a generally stable shelf between a rise in the NNE (the Asturian Geanticline) and a curved geosyncline (present at least until the Devonian) in the SSW. Unstable conditions prevailed during the Upper Cambrian and the Couvinian-Givetian.\nThe Asturian Geanticline extended several times towards the SSW, which resulted in emergence, accompanied by erosion, of the Luna-Sil region during the Llanvirn-Llandovery, during the Gedinnian (only the NNE part) and at the end of the Devonian. The last epeirogenic uplifts resulted in strong erosion, especially in the NNE part of the region: Famennian-Tournaisian deposits unconformably overlie rocks of a Gedinnian age. These uplifts occurred along fundamental faults. Slight epeirogenic uplifts along the same faults during the Lower Vis\xc3\xa9an resulted in the erosion of the very thin black shales of a Tournaisian age.\nWith the beginning of the greywacke deposition during the Upper Namurian B, initial to the folding and thrusting of the region, the palaeogeographic pattern changed: the source area was now situated in the SSW, while a rapidly subsiding basin lay in the place of the former shelf. The line of maximum sedimentation, just as the folding front, was displaced during the Namurian and Westfalian from SSW to NNE. After the orogenesis, followed by strong erosion, oblong basins developed along normal faults approximately parallel to the strike of the orogene, in which thick coal-bearing sediments accumulated during the Stephanian B and C; these sediments were folded during the Lower Permian.\nDuring the orogenesis thrusts were formed, generally parallel to the strike of the former curved basin, which developed from the breaking through of anticlines. These folds and thrusts have their vergence to the NNE. The shape and amplitude of the folds were mainly determined by a thick Ordovician quartzite formation. During the folding and thrusting a tectonic \xe2\x80\x98Stockwerk\xe2\x80\x99 was formed in the Palaeozoic rocks, each of the 11 levels in this \xe2\x80\x98Stockwerk\xe2\x80\x99 possessing its own tectonic style. During continued compression, movement along the thrust faults ceased and these faults were involved in the folding. This last stage of the folding has its vergence to the SSW.\nOne important and a number of less important WSW trending faults cross the folds and thrust faults which are generally parallel to the chiefly WNW strike of the former curved basin. Due to a reorientation of the stress field in a direction perpendicular to the WSW trending faults, deviation of the generally WNW trending structures took place in a direction parallel to these faults. This deviation is strongest near the ends and nil in the central parts of the WSW trending faults.