Resumen de Tesis Doctoral: Evolución tectonosedimentaria de la cuenca Terciaria de As Pontes (NW de España)

BERNAT FERRÚS I PINYOL

Abstract


The oligo-miocene As Pontes strike-slip basin (Galicia, NW Spain) is a first order coal-field in the Iberian Peninsula. Their structural and sedimentary features are genetically related to the evolution of a NW-SE dextral strike-slip fault system located in NW Galicia. This contribution deals with the analysis of structural evolution, stratigraphic framework and tectonics-sedimentation relationships in the basin. The structural evolution recorded in the basin is characterised by two evolutionary stages. The sedimentation began in two sub-basins located in a compressive relay of two main strike-slip faults, and their conve rgence led to a second stage characterised by a restraining bend strike-slip fault geometry. The preserved basin fill records syntectonic activity during 7,4 My, between 29,8 My (near the Rupelian-Chattian boundary) to 22,4 My (Aquitanian). A sequence stratigraphy subdivision of the basin fill has been carried out in order to set up a hierarchy of genetic stratigraphic units. The subdivision is based on the spreading-retreat trends affecting the palustrine-lacustrine systems. These stratigraphic units can be either simple (elemental sequences) or complex (composite sequences, macrosequences and megasequences). Tectonics was the main control on the sequence arrangement recorded in the basin, and acted in an ensemble of diverse overlapped spatial and temporal scales, controlling subsidence and uplift rates, that in its turn influenced sediment and water inputs. These factors altogether caused the alluvial-fan progradation-retrogradation trends, and also the spreading-retreat trends of the lacustrine-palustrine systems. Autogenic controls (differential compaction, alluvial fan dynamics) and climate represent minor controls, and probably their effects were partially concealed by tectonic effects, even in the elemental sequences order.

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