A coarsening-upward megasequence generated by a Gilbert-type fan-delta in a tectonically controlled contex (Upper Miocene, Guadix-Baza Basin, Betic Cordillera, southern Spain)

Abstract

The 100 m thick succession at Bodurria of a Gilbert-type fan-delta constitutes an Upper Tortonian, coarsening- and thickening-upward megasequence. It lies uncofor mably converted by the continental Pliocene. Neogene materials of the basin infill, and is uncomformably covered by the continental Pliocene. The succession was deposited on one margin of an extension basin, with ac tive sysedimental techonics and rosing sea-level. In these circumtances the accommodation space and the sudiment supply increased throughhout time. This determined the development of the coarsening and thickening upwward megasequence, resulting from the vertial stacking of four smaller sequences which in turn, were built by staking of Gilbert-tpe fan-delta units and were bounded by calcarenite facies deposited on a shallow shelf. This sequential organisation and internal structure were controlled by the tectonic behaviour of the faults on the basin margin, in particular large-scale movements with intervals of stability, which respectively created accommodation space for the deltaic sequences and conditions for development of calcarenite shelf facies.