Cantos blandos en tempestitas con estructuras sedimentarias de deformación (Mioceno, Cuenca del Guadalquivir; Porcuna, provincia de Jaén)

Abstract

Mud pebbles in Upper Miocene calcarenitic tempestites with soft-sediment deformation structures of the Guadalquivir Basin (Southern Spain) are analysed. The mud pebbles are always restricted to part of the stratigraphic sections, in exclusive association with calcarenitic tempestites with softdeformation structures. They are interpreted as the result of erosion of marls, interbedded between the dominant calcarenites, both with a low degree of lithitication. This marls were eroded by storms and redeposited as rip-up clasts. In the soft-sediment deformation structures the liquefaction of the calcarenites with the mud pebbles was triggered by pore pressure changes induced by cyclic and residual stress of storm waves. The upper part or the complete beds of previous storm events were reworked and redeposited by later depositional storm events with the mixture of older and subsequent sediments. The amalgamated nature of these deposits shows that the building of these beds implied multiple processes of erosion, deposition and liquefaction, related to the effect of individual storms or periods of important storms. The mud pebbles horizons represent a substantial loss in stratigraphic resolution due to widespread erosion of the marls deposited in the carbonate ramp.