RT Journal Article
T1 Tectono-thermal evolution in a region with thin-skinned tectonics:the western nappes in the Cantabrian Zone (Variscan belt of NW Spain)
A1 Bastida Ibáñez, Fernando
A1 Brime Beteta, Begoña
A1 García López, Sofía
A1 Sarmiento Chiesa, Graciela Noemí
AB The palaeotemperature distribution in the transition from diagenesis to metamorphism in the western nappes of the Cantabrian Zone (Somiedo, La Sobia and Aramo Units) are analysed by conodont colour alteration index (CAI) and illite crystallinity (IC). Structural and stratigraphic control in distribution of CAI and IC values is observed. Both CAI and IC value distributions show that anchizonal conditions are reached in the lower part of the Somiedo Unit. A disruption of the thermal trend by basal thrusts is evidenced by CAI and IC values. There is an apparent discrepancy between the IC and CAI values in  carboniferous rocks of the Aramo Unit; the IC has mainly anchizonal values, whereas the CAI has diagenetic values. Discrepant IC values are explained as a feature inherited from the source area. In the Carboniferous rocks of the La Sobia Unit, both IC and CAI indicate diagenetic conditions. The anchimetamorphism predated completion of emplacement of the major nappes; it probably developed previously and/or during the early stages of motion of the units. Temperature probably decreased when the metamorphosed zones of the sheets rose along ramps and were intensely eroded. In the context of the Iberian Variscan belt, influence of tectonic factors on the metamorphism is greater in the internal parts, where the strain and cleavage are always present, than in the external parts (Cantabrian Zone), where brittle deformation and rock translation are dominant, with an increasing role of the burial on the metamorphism.
PB Springer Science Business Media
SN 1437-3254
YR 1999
FD 1999
LK https://hdl.handle.net/20.500.14352/60430
UL https://hdl.handle.net/20.500.14352/60430
LA spa
DS Docta Complutense
RD 18 abr 2025