SOFT-SEDIMENT DEFORMATION STRUCTURES INDUCED BY EARTHQUAKES (SEISMITES) IN PLIOCENE LACUSTRINE DEPOSITS (GUADIX-BAZA BASIN, CENTRAL BETIC CORDILLERA)

The Guadix-Baza intramontane basin,located in the central sector of th e Betic Cordillera (Southern Spain) contains Pliocene lacustrine and a lluvial sediments in its central and marginal areas, respectively. The Pliocene sediments contain many soft-sediment deformation structures, mainly located at the marginal sites of Guadix-Baza paleo-lake. This area is characterised by sandy, silty and clayey sediments with rare g ravel horizons. The soft-sediment deformation structures include: load casts, pillows and water-escape structures, all indicative of sedimen t liquefaction or fluidization. An evaluation of these structures sugg est that storm waves, overloading and artesian spring action can be re jected as possible genetic mechanism. Regional considerations favour t ectonic activity during the Pliocene in this sector of the Betic Cordi llera as the cause of the soft-sediment deformation structures in the Guadix-Baza basin, i.e. moderate-high magnitude seismic shocks.