Soft-sediment deformation structures induced by cyclic stress of storm waves in tempestites (Miocene, Guadalquivir Basin, Spain)

The identification of triggering agents for soft-sedimentation structures i s an enigmatic geological problem. Mainly seismic-induced soft-sediment str uctures have been recognized in ancient sediments, rather than those result ing from storm waves. We analyse soft-sediment deformation structures in up per Miocene calcarenitic tempestites of the Guadalquivir Basin (Southern Sp ain). The most common structures are load-casts which vary in height and wi dth from 10 centimetres to several metres. The structures are always restri cted to a small part of the stratigraphic sections, in exclusive associatio n with tempestites. The analysed soft-deformation structures are interprete d to be the result of liquidization processes. Chiefly from their inferred depositional environment, and subordinately from the deformation style, we have devised basic criteria to identify the trigger mechanism, in these sof t-sediment deformation structures the liquefaction was triggered by pore pr essure changes induced by cyclic and residual stress of storm waves.