Subsidence analysis, maturity modelling and hydrocarbon generation of the Alpine sedimentary sequence in the NW of the Iberian Ranges (Central Spain)

Abstract

The burial, thermal and hydrocarbon histories of late Permian-Tertiary sedimentary succession in the NW of the Iberian Ranges were investigated using a single-well model. The reconstructed geobistories indicate four stages of evolution during early Alpine to late Alpine infill in the studied area: late Permian, Triassic, early and middle Jurassic, and latest Jurassic-middle Cretaceous. The differences between interpreted basement behaviour interpreted from tectonic subsidence curves differentiates four major «rift-uplift realms». The «riftluplift» realm is defined either as an individual fault-bounded structural domain of ifie continental phase of the rift system or as an uplift that displays similar extensional/uplift proeesses. Thcse «riftluplift realms» show a propagation of rifting/uplift stages through time. The initial Permian, Triassic and Jurassic episodes show a north-eastem propagation foliowed by a south-western propagation from the Central realm. Each of these realms shows aLo a gradual north-eastern progress of the extension strain. The Cretaceous rift/uplift stage seems to behave in the opposite direction. Present day bottom heat flow and thermal history were modelled, using both a steady sUite thermal aud a paleothermal heat flow-invariant model. Thc present average bottom heat flow oblained faills within the range of values reported in the literature from similar tectonic contexts. Different hcat flow values were tentatively adopted to determine maturation. Ml the quantitative estimations of generated hydrocarbons indicate that insignificant volumes of hydrocarbons were generated by source rocks considered in this study.